Convective outflow boundaries emanating away from thunderstorms are generated as cold, dense air descends in downdrafts then moving outward away from the convection to produce a mesoscale cold front also known as a gust front. Some gust fronts can be completely harmless or may be a precursor for an encounter with severe turbulence and dangerous low-level convective wind shear. The direction of movement of the gust front isn’t always coincident with the general motion of the thunderstorms. If the gust front is moving in advance of the convection, it should be strictly avoided. The pilot’s best defense is to recognize and characterize the gust front using METARs, ground-based radar and visible satellite imagery.

According to research meteorologist and thunderstorm expert, Dr. Charles Doswell, “cold, stable air is the ‘exhaust’ of deep, moist convection descending in downdrafts and then spreading outward like pancake batter poured on a griddle.” As a pulse-type thunderstorm reaches a point where its updraft can no longer support the load of precipitation that has accumulated inside, the precipitation load collapses down through the original updraft area. Evaporation of some of the rain cools the downdraft, making it even more dense compared to the surrounding air. When the downdraft reaches the ground, it is deflected laterally and spreads out almost uniformly in all directions producing a gust front. 

• READ MORE: Keeping an Eye on the Storm

Gust fronts are normally seen moving away from weakening thunderstorm cores. Once a gust front forms and moves away from the convection the boundary may be detected on the NWS WSR-88D NEXRAD Doppler radar as a bow-shaped line of low reflectivity returns usually 20 dBZ or less. Outflow boundaries are low level events and do not necessarily produce precipitation. Instead, the radar is detecting the density discontinuity of the boundary itself along with any dust, insects and other debris that may be carried along with the strong winds within the outflow. The gust front in southwest Missouri shows up very well on the NWS radar image out of Springfield as shown below. 

 An important observation is to note the motion of the gust front relative to the motion of the convection. In this particular case, the boundary is steadily moving south while the thunderstorm cells that produced the gust front are moving to the east. This kind of outflow boundary is usually benign especially as it gains distance from the source convection. On the other hand, a gust front that is moving in the same general direction in advance of the convection is of the most concern. These gust fronts often contain severe or extreme turbulence, strong and gusty straight line winds and low-level convective wind shear. 

As mentioned previously, gust fronts are strictly low-level events. As such, even the lowest elevation angle of the radar may overshoot the boundary if it is not close to the radar site. Shown above at 22Z, the NWS WSR-88D NEXRAD Doppler radar out of Greenville-Spartanburg, South Carolina is the closest radar site and clearly “sees” the gust front (right image). However, the NEXRAD Doppler radar out of Columbia, South Carolina (left image), is further away and misses the gust front completely. As the gust front moves away from the radar site, it may appear to dissipate, when in fact, the lowest elevation beam of the radar is simply overshooting the boundary. 

As a result, it is important to examine the NEXRAD radar mosaic image before looking at the individual radar sites.

Not all gust fronts are easy to distinguish on visible satellite imagery; the gust front could be embedded in other dense clouds or a high cirrus deck may obscure it. It is also possible that the boundary may not have enough lift or moisture to produce clouds. In many cases, however, it will clearly stand out on the visible satellite image. When the gust front contains enough moisture, as it was in this situation, cumuliform clouds may form along the boundary and move outward. This is very common in the Southeast and coastal regions along the Gulf of Mexico given the higher moisture content.  

As this particular gust front passed through my neighborhood located south of Charlotte, North Carolina, strong, gusty northerly winds persisted for about 10 minutes. As is common, the main core of the precipitation didn’t start to fall for another 10 minutes. When a gust front such as this appears on satellite or radar, it is important to monitor the METARs and ASOS or AWOS closely for the occurrence of high winds. Several airports in the vicinity reported wind gusts peaking at 30 knots. The sky cover went from being just few to scattered clouds to a broken sky with these cumuliform clouds moving rapidly through the region.

• READ MORE: The Ins and Outs of Pilot Weather Reports

As mentioned earlier, a gust front moving away from thunderstorms is a low-level event that can contain very strong updrafts and downdrafts. The graph shown above is a time series, plotting the upward and downward motion or vertical velocity in a strong gust front as it moved over a particular point on the ground. The top half of the graph is upward motion and the bottom half is downward motion. 

Time increases from left to right. As the gust front approaches, the vertical velocity of the air upward increases quickly over a one or two minute period. While the maximum vertical velocities vary with height in the outflow, a common maximum number seen is 10 m/s at about 1.4 km or 4,500 feet agl (25 knots is roughly 12 m/s for reference). As the gust front moves through, the velocities abruptly switch from an upward to a downward motion creating strong wind gusts at the surface. Most outflow boundaries don’t extend above about 2 km or 6,500 feet agl. What is remarkable is that upward to downward motion changes in just about 30 seconds over the ground point where this was observed. But imagine flying an aircraft at 150 knots through this; the up and down exchange will happen in just a few seconds producing a jarring turbulence event.

Just in case you were wondering, gust fronts are conveniently filtered out by your datalink weather broadcasts as shown above for XM-delivered satellite weather. This is because the broadcast only provides returns from actual areas of precipitation. Often outflow boundaries or gust fronts produce low reflectivity returns that fall below the threshold used to filter out other clutter not associated with actual areas of precipitation. When in flight, pay particular attention to surface observations looking for strong, gusty winds before attempting a landing at an airport when storms are approaching. 

This feature first appeared in the July/August Issue 949 of the FLYING print edition.

The post Know Your Convective Outflow Boundaries appeared first on FLYING Magazine.

Answer: There are many observed cases of lightning strikes to aircraft inside or near clouds that had not previously produced natural lightning. Studies show that about 90 percent of the lightning strikes to aircraft are thought to be initiated by the presence of the aircraft itself. The scary statistic, however, is that 40 percent of all discharges involving airborne aircraft occurred in areas where no thunderstorms were reported.

Apollo 12

One of the more famous cases of aircraft-initiated lightning is the Apollo 12 launch at the Kennedy Space Center, Florida, in November 1969. The Saturn V rocket was struck not once but twice on its way into orbit.

According to the 1970 NASA findings, other than these two strikes, there was no other lightning activity reported six hours before or six hours after the launch. At the time of the launch, a cold front was moving south into the launch area. Broken towering cumulus topping out at 23,000 feet with light to moderate rain showers were reported.

Rarely Fatal

Damage to airborne aircraft struck by lightning includes minor pitting or scarring to the aircraft’s skin to complete destruction of the aircraft.

Besides direct damage at the point of entry and/or exit, indirect effects that include the loss of VHF communication, loss of navigation equipment, and loss of instrument panel gauges are also possible.

In 1963, a Pan American Airlines Boeing 707 over Elkton, Maryland, was struck by lightning while in a holding pattern at 5,000 feet. The outermost fuel tank in the left wing exploded causing two other fuel tanks to follow suit. There were no survivors.  

• READ MORE: Does the FAA Punish Pilots for Logbook Mistakes?

It’s certainly true that a catastrophic accident such as this is extremely rare, but lightning strikes to aircraft are more common than you might imagine—most of which are aircraft-initiated strikes.

Based on compiled data it is estimated that in the U.S. a commercial airliner is struck once for every 3,000 hours flown. That’s an equivalent of about one strike each year. 

Melting Level

While aircraft-initiated lightning is still being actively studied, there are a few important characteristics to consider.

Based on the current research, it doesn’t take flying in or near a mature thunderstorm to become the victim of a lightning strike. The mere presence of the aircraft in an environment conducive to an electrical discharge is all that is necessary.

Most of the aircraft-initiated lightning strikes occur when the aircraft is flying at or near the melting level (0 degrees Celsius). The preferred temperatures include a range from plus-3 C to minus-5 C, with the highest number of incidents occurring right at the melting level.  

A few of the strikes down low are the result of an aircraft intercepting a lightning strike in progress. Essentially, this is the case of being in the wrong place at the wrong time.

On the other hand, aircraft-initiated strikes are observed the most are between 3 km and 5 km or 10,000 to 16,000 feet during the warm season. Once again, temperature is a key factor. The melting level that typically occurs is in this same range of altitudes throughout the summer months.  

Low-Topped Convection

In general, natural lightning in deep, moist convection doesn’t form until the tops of the storm build well above the melting level.

For lightning to form, three ingredients must be simultaneously present. These include vapor-born ice crystals, graupel, and supercooled liquid water. If any one of these three is missing in sufficient quantities, natural lightning doesn’t generally occur, but this not to say the cloud is void of all electrical activity—some still remains.    

Therefore, an aircraft-initiated lightning strike typically occurs within local air mass instability within low-topped convection.

Often low-topped convection doesn’t produce natural lightning. The updrafts are rather weak in comparison to those that do produce lightning. Consequently, the updrafts do not carry enough supercooled liquid water into the upper part of the cloud where it is needed. 

• READ MORE: What Are Echo Tops?

Clouds and Precipitation

An overwhelming number of lightning strikes occur within the cloud itself. Only a very small percentage of strikes occur outside of the cloud boundary or below the cloud.

Here’s the key: A very large percentage of the strikes occur within precipitation to include rain, snow, snow grains, ice pellets, and hail. It is not uncommon to find a mixture of these near the melting level. 

Keep Your Distance?

The FAA encourages all pilots to keep a safe distance from an active thunderstorm for obvious reasons.

Unfortunately, this practice alone isn’t quite enough. Even when thunderstorms (natural lightning) are not occurring or expected to occur, an aircraft-initiated lightning strike can still be a risk.

In order to avoid an encounter with lightning, the best advice is to remain in cloud-free air whenever possible, especially when the atmosphere is conditionally unstable and capable of producing marginally deep, moist convection extending well above the melting level.

While it may be difficult, the best advice is to operate outside of areas of precipitation and minimize your time in clouds and precipitation near the melting level.

The post How Can an Aircraft Get Struck by Lightning Without a Close Thunderstorm? appeared first on FLYING Magazine.

Answer: The short answer is no. Echo top height is a volume product that originates from the NWS WSR-88D NEXRAD Doppler radars.

This is the same network of radars that is used to build the familiar radar mosaic pilots readily use in the cockpit. While not provided in the FIS-B broadcast, the echo top height product, however, is arguably the most misused data that is broadcast by SiriusXM to your satellite-based weather receiver.

Despite what many pilots are taught, this product does not represent the height of the cloud tops and should never be used as such since it is often likely to produce unreliable and inconsistent results.

When looking at any ground-based radar depiction, the colors you see are mapped to a quantity in decibels of Z, often abbreviated dBZ, where Z is the reflectivity parameter. As the name implies, reflectivity is the amount of energy that is returned (reflected) back to the receiver after hitting a target.

For precipitation, these targets are called hydrometeors that include rain, snow, ice pellets, and hail. There are a few exceptions, but generally speaking, the higher the dBZ value, the heavier the precipitation.

All deep, moist convection or thunderstorms have both a cloud top (the highest point of the cloud as measured from sea level) and top of the precipitation core within the convection. The “top” of the precipitation core is defined as the msl height of the highest radar reflectivity of 18 dBZ. This altitude is referred to as the echo top height.   

For example, imagine taking a vertical “slice” through a typical thunderstorm, such as the one shown above. The white dashed line shows the west-to-east slice with the echo top height shown on the left and the base reflectivity from the lowest elevation angle shown on the right. The radar depiction on the right is the view most familiar to a pilot.

However, to better illustrate how the echo tops are determined, the depiction below is this same slice from above that is shown as a vertical cross section of the radar reflectivity. In other words, it depicts all possible elevation angles from the radar’s volume scan through this slice.

The colors are the reflectivity values in dBZ. The highest values shown in the precipitation core are about 55-60 dBZ and are all below about 7 kilometers (about 23,000 feet). As height increases in the core, notice the values drop off to less than 15 dBZ.

By connecting the points where the values in the core drop off to the 18 dBZ value, this represents the echo top height (shown by the white squiggly line). For this cell, the highest point in this cross-section is 17 kilometers or roughly 56,000 feet msl.

Cloud top height, on the other hand, is higher than the echo top height. In fact, it can be 5,000 to 10,000 feet higher in some of the most intense storms.

The visible satellite image below is a good example of thunderstorms with overshooting tops. Given the time of day, the highest tops actually cast a shadow on the thunderstorm anvil. This is the column of air in the thunderstorm that will usually have the highest echo tops due to the vigorous updraft. 

Echo top heights are specifically used by forecasters to identify the most significant storms by locating the highest echo regions. Stronger updrafts are seen in regions where the highest echo tops are located.

Moreover, the parameter that has the highest apparent correlation with lightning is not the highest cloud top but rather the highest detected radar echo top of 30 dBZ or greater.

Shown above is the SiriusXM composite radar mosaic shown with the Garmin Pilot app. In addition to the radar reflectivity, storm cell identification tracking (SCIT) markers are shown.

These attempt to identify the movement and echo top height of various cells in the radar mosaic. The height provided is measured in hundreds of feet. If there’s an arrow, this defines the direction of movement, and the end of the arrow represents where the cell might be located in the next 60 minutes given its current speed and direction of movement.  

Lastly, this may seem obvious, but echo tops are not going to help identify the vertical extent of many weather systems unless those clouds are producing some kind of precipitation in the form of rain, snow, hail, or ice pellets.

Therefore, a stratus deck, even one that has some depth, won’t likely be picked up by the radar. In fact, it’s not likely you will see echo tops shown below 20,000 feet because of this. Echo tops are more appropriate for convective precipitation where the clouds have significant vertical depth.  

The post What Are Echo Tops? appeared first on FLYING Magazine.

Avoid thunderstorms. This stark statement that has been thrown at pilots over the last century portends danger and seems like a reasonably cut-and-dried message. This is understandable, although it misses the mark, and it’s not the most complete message to send to pilots. There’s more to the story that has yet to be told.

The National Severe Storm Laboratory (NSSL) defines a thunderstorm as “a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lightning.” You may have just chuckled reading this definition. However, “rain shower” is the key phrase to notice. In other words, one minute before the first lightning strike, it technically cannot be called a thunderstorm. Instead, it’s called a rain shower. A rain shower may be just as dangerous as—and may be more dangerous than—a thunderstorm. The new narrative that should be shouted from the tops of the airport hangars is to “beware of the benign.”

From the outset, understand that showery precipitation is, by definition, a form of moist convection. It may be shallow in thickness, or rather deep. A thunderstorm is a specific class of deep, moist convection, namely one that contains lightning. Shallow, moist convection might lead to a rough ride, but won’t likely contain jarring convective turbulence. Deep, moist convection, on the other hand, is bad news. And while no two rain showers are alike, avoidance is strongly encouraged with or without lightning.

In fact, during the summer you may hear your local broadcast meteorologist or weather personality say during the news, “expect scattered showers this afternoon.” The term “showers” tends to be glossed over by many pilots as a benign weather condition. Pilots should translate this as, “expect scattered deep,moist convection this afternoon,” since rain showers and thunderstorms are, for all intents and purposes, one and the same from a pilot’s perspective. In fact, not too many decades ago, the term “thundershowers” was commonly used but was slowly abandoned in favor of the phrase “showers and thunderstorms.” While there is a technical difference between a rain shower and thunderstorm, it’s not a technicality that should matter to a pilot. Both should be treated the same and avoided.

Convective Precipitation

As the sun beats down on the earth’s surface during the day, an imbalance in temperature is created. The convective process that starts out as dry eddies transfers heat energy away from the surface to reduce this imbalance, through a process called convection. These dry eddies—more commonly called thermals—expand and cool as they ascend and may reach saturation to produce shallow, moist convection called cumulus clouds. When there’s mid-level instability aloft or some form of outside energy contribution available (e.g., a frontal system), these clouds can grow into congested or towering cumulus, which is referred to as deep, moist convection. At this point in the convective process, an aircraft flying through these clouds may encounter severe or extreme turbulence. But what few pilots appreciate is that they can also produce microbursts be-low these deep convective clouds when the precipitation core falls out of these clouds to the surface.

Convective precipitation can be characterized in one extreme as the coalescence of raindrops formed where the temperature profile within the cloud is warmer than 0 degrees Celsius. This is the kind of showeryprecipitation you might get in tropical areas such as Hawai‘i or the Caribbean. At the other extreme is convection that occurs at temperatures well below 0 degrees Celsius within most of the cloud, with all of the precipitation originating in the ice phase including snow and graupel, a form of soft hail.

Significant electrification in moist convection occurs as a result of bouncing collisions between smallice (solid) and graupel that grow at the expense of supercooled cloud drops (liquid). Within the cloud, this is followed by the gravitational separation of charged particles that enable the discharge we call lightning. To get electrified convection (i.e., a thunderstorm),the cloud top temperature needs to be sufficiently cold enough to support precipitation originating in the ice phase. These conditions occur in deep, moist convective updrafts. However, when tops are not as cold (not as high), lightning may be absent. This is what meteorologists label low-topped convection.

So, all thunderstorms begin as rain showers. However, not all rain showers grow up to be mature thunderstorms. In other words, a little rain shower is the beginning of the mature stage of the convective process and should be viewed as such. As a rain shower deepens, it can develop dangerous convective turbulence.

Drs. Ted Fujita and Fernado Caracena stated long ago that most microbursts occur from benign-looking cells. You may recognize the name Fujita. Dr. Fujita was the research meteorologist and professor at the University of Chicago who defined the microburst. The way tornado intensity is quantified today is named after him, namely, the Fujita scale.

He defined the microburst as a violent outflow from convection that occurs on a spatial and temporal resolution of 1 to 4 km and 2 to 5 minutes, respectively. To put that into perspective, a microburst is about the size of the runway complex at most medium to large airports and occurs within a timeframe of an aircraft on a five-mile final approach to land.

Here’s the problem. Pilots—whether flying light, medium, or heavy aircraft—will not be bitten by a supercell thunderstorm. That’s because those storms look ugly, and we want to avoid them. However, a benign-looking cell such as a high-based rain shower is far more inviting. The high base gives the pilot the impression it’s safe to fly under and lures them into a false sense of security. Often, there’s no visible rainshaft present until it’s too late

The Microburst Threat

Here’s a quote from an article written by Captain William W. Melvin entitled, “Wind Shear Revisited.” It appeared in the November 1994 issue of Air Line Pilot Magazine: “Many pilots have been trained to avoid large supercell-type thunderstorms in the belief that this will prevent encounters with microbursts. Yet no evidence exists that any of the known microburst encounters have occurred in supercell storms. Dr. Ted Fujita and Dr. Fernando Caracena, recognized authorities in this field have repeatedly emphasized that microbursts are frequently generated from benign-appearing cells. Many ‘experts’ who disagree with Drs. Fujita and Caracena have empha-sized the supercell storms with warnings of dangers of gust fronts. These so-called experts are leading pilots down the primrose path for microburst encounters.”

Convection with high cloud bases is a perfect environment for the birth of a microburst. Often, the air below the convective cloud is relatively dry. However, there’s no accepted definition for the depth of this dry air before it portends danger. A good example of such an environment was on August 2, 1985, in Dallas, Texas, around 6 p.m. CDT. The surface temperature and dew point were reported at 101 degrees Fahrenheit and 65 degrees Fahrenheit, respectively, just before Delta Air Lines Flight 191 succumbed to a microburst while the Lockheed L-1011 was on approach to Dallas-Fort Worth International Airport (KDFW). This is a dewpoint depression of 35 degrees, equating to a relative humidity of 31 percent at the surface. In other words, extremely dry air was in place over the airport. The estimated ceiling at KDFW shortly before the accident was broken at 21,000 feet. This certainly would not appear threatening and is far from being a supercell event. 

Those dry conditions allow for evaporative cooling to occur. Essentially as the precipitation core begins to fall out of the base of the cloud into this very dry air, the raindrops begin to undergo rapid evaporation. Evaporation is a cooling process making the descending air below the cloud base denser and heavier. This allows the shaft of cold air falling out of the convection to accelerate rapidly toward the surface, sometimes with a speed of 100 miles per hour or more. While microbursts can and do occur within supercell thunderstorms, pilots and crews are more likely to discount potential danger with benign-appearing cells. Many of these are low-topped convective rain showers, often with a lot of blue sky throughout the area.

This is not to say that every benign-appearing cell will produce a microburst. However, microbursts are not as rare as most pilots assume. I remember one long cross-country training flight with an instrument student from Chicago Executive Airport (KPWK) to Eagle, Colorado. We had planned a quick fuel stop in Nebraska. When we arrived, nearly a dozen cells were in the vicinity, including a thunderstorm hanging out over our destination. With my student under the hood, I took this opportunity to give him a chance to ask ATC for a hold so we could decide the best course of action, since our planned destination wasn’t viable. While we were making perfect wind-corrected one-minute turns at 8,000 feet in the hold with blue sky above us, I saw at least five dry microbursts occur in the distance in a span of about 10 minutes. I saw a circular ring of dust on the surface appear underneath benign-seeming cells. The cloud bases were about 12,000 feet.

We diverted to a different airport and asked ATC for a practice ILS approach. After landing, we tied the aircraft down on the ramp and started to walk to the FBO, only to be met with a blast of sand and dust at our backs that was so intense we couldn’t pull open the door to the FBO to escape it. I wouldn’t have wanted to tangle with that on final approach. It was likely the result of another dry microburst nearby. Given their small scale, microbursts may go unnoticed unless they occur near a major airport or cause damage to a populated area. If you Google “microburst damage” you will find countless pictures of the extreme damage they can cause to vegetation and structures, sometimes more than you’d see with a small tornado. Given that they occur on such small spatiotemporal scales, they are also quite difficult to detect so that pilots can be given sufficient advance warning.

One of the best utilities to detect microbursts (wet or dry) as they happen is terminal Doppler weather radar (TDWR). These are located near many high-impact airports throughout the U.S. and have a range of 60 nm. Unlike the airport surveillance radar (ASR) typically collocated on the field, TDWR is typically sited about six to seven miles from the airport so that it is in a position to scan the primary approach and departure corridors. TDWR can detect and track convective outflow boundaries (gust fronts) and microbursts and provide an alert to controllers, which can be relayed to the pilot.

A Healthy Respect

Most pilots are used to looking at the Nexrad surveillance scan of the radar that measures the base reflectivity. However, it’s the Doppler scan of the TDWR that is the crown jewel when it comes to detecting a microburst. This is referred to as the base velocity data. A microburst is a rush of concentrated air flowing nearly straight down (although there can be rotation of this air) out of the cell that may strike the surface and spread outward like pouring pancake batter on a griddle.

The velocity data does not show the velocity of the downward motion of the air itself. It simply quantifies the magnitude of the velocity component of the wind toward or away from the radar site, once the air from the microburst or downburst is moving horizontally. And, as the microburst begins to move outward, those hydrometeors (raindrops, dust, sand, insects, etc.) intersect the radar beam and are detected and show up with a classic dual node signature. This signature can be quickly detected by TDWR, with subsequent alerts generated. Hydrometeors that move tangentially to the radar beam show up as zero velocity, although the actual magnitude of the wind in that direction may be extreme.

It’s fair to say that most seasoned pilots have a healthy respect for Mother Nature, especially as it relates to deep, moist convection. But it doesn’t take a full-blown supercell thunderstorm to ruin your day. Please beware of the benign.

This article was originally published in the March 2023 Issue 935 of  FLYING.

The post Beware of the Benign appeared first on FLYING Magazine.

Answer: It depends on your mission and how many Ben Franklins you have to spare. Your sferics (short for radio atmospherics) equipment may represent the only real-time weather you’ll ever see in your cockpit.

Sure, panel-mounted and portable weather systems deliver their product in a timely fashion, but it will never be as immediate as your sferics device. Once you understand how to interpret your real-time lightning guidance, it can become a valuable asset in your in-flight aviation toolkit. 

Choices in the Cockpit

You have two options if you want lightning data in the cockpit: You can choose from ground-based lightning sensors or onboard lightning detection from a sferics device such as a Stormscope.

A Stormscope provides real-time data but does require some basic interpretation. Ground-based lightning, on the other hand, is a bit delayed and is only available through a data link broadcast at this time. Ground-based lightning is normally coupled with other weather guidance, such as ground-based weather radar (NEXRAD), surface observations, pilot weather reports, and other forecasts.   

Ground-Based Lightning

The ground-based lightning that’s now available through the Flight Information System-Broadcast (FIS-B) comes from the National Lightning Detection Network (NLDN). This network of lightning detectors has a margin of error of 150 meters for locating a cloud-to-ground strike. The ground-based lightning sensors instantly detect the electromagnetic signals given off when lightning strikes the earth’s surface.    

With 150-meter accuracy, I’d choose ground-based lightning any day. Don’t get too excited, though. Ground-based lightning is expensive (the data is owned by private companies like Vaisala), and you’ll not likely see a high-resolution product in your cockpit anytime soon.

SiriusXM satellite weather pulls from a different lightning detection network and includes both cloud-to-ground and intracloud lightning. It produces a 0.5 nm horizontal resolution lightning product. This means that you will see a lightning bolt or other symbol arranged on your display in a 0.5 nm grid.

Even if 50 strikes were detected minutes apart near a grid point, only one symbol will be displayed for that grid point. Same is true for the FIS-B lightning.

Stormscope Advantages

A Stormscope must be viewed as a gross vectoring aid. You cannot expect to use it like onboard radar.

Nevertheless, it does alert you to thunderstorm activity and will provide you with the ability to see the truly ugly parts of a thunderstorm.  Where there’s lightning, you can also guarantee moderate or greater turbulence.   

No lightning detection equipment shows every strike, but the Stormscope will show most cloud-to-ground and intracloud strikes. This allows you to see the intensity and concentration of the strikes within a cell or line of cells with a refresh rate of two seconds. It also lets you see intracloud electrical activity that may be present in towering cumulus clouds even when no rain may be falling.

Even if no cloud-to-ground strikes are present, intracloud strikes may be present. The Stormscope can detect any strike that has some vertical component (most strikes do). This is important since there are typically more intracloud strikes than cloud-to-ground strikes.

To emphasize this point, most of the storms in the Central Plains have 10 times more intracloud strikes than cloud-to-ground strikes. Moreover, during the initial development of a thunderstorm, and in some severe storms, intracloud lightning may dominate the spectrum. 

Also keep in mind that a sferics device does not suffer from attenuation like onboard radar. That is, it can “see” the storm behind the storm to paint cells in the distance out to 200 nm, but it does not see precipitation or clouds.     

Stormscope Disadvantages

It doesn’t take a full-fledged storm, complete with lightning, to get your attention.

Intense precipitation alone is a good indicator of a strong updraft (or downdraft) and the potential for moderate to severe turbulence in the cloud. Consequently, the Stormscope does not tell you anything about the presence or intensity of precipitation or the absence of turbulence.

Never use the Stormscope as a tactical device to penetrate a line of thunderstorm cells. Visible gaps in the cells depicted on the Stormscope may fill in rapidly. Fly high and always stay visual and you will normally stay out of any serious turbulence.        

A Stormscope display is often difficult to interpret by a novice. Radial spread, splattering, buried cables, and seemingly random “clear air” strikes can create a challenge for the pilot. It may take a couple years of experience to be completely comfortable interpreting the Stormscope display. Often what you see out of your window will confirm what you see on your display.    

Radial Spread

As the name suggests, the biggest Stormscope error is the distance calculation along the radial from the aircraft.

The placement of the strike azimuthally is pretty accurate. However, how far to place the strike from the aircraft along the detected radial is a bit more complicated and prone to error.

Lightning strikes are not all made equally. When the sferics devices were invented back in the mid-1970s, they measured the distance of the cloud-to-ground strike based on the strength of the signal (amperage) generated by the strike. An average strike signature of 19,000 amperes is used to determine the approximate distance of the strike.

Statistically, 98 percent of the return strokes have a peak current between 7,000 and 28,000 amperes. That creates the potential for error in the distance calculation. This error is a useful approximation, however, in that strokes of stronger intensity appear closer and strokes of weaker intensity appear farther away. 

In strike mode on the Stormscope, strikes are displayed based on a specific strike signature, whereas cell mode on the newer Stormscope models uses a clustering algorithm that attempts to organize these strikes around a single location or cell.

Cell mode will even remove strikes that are not part of a mature cell. Most thunderstorm outbreaks are a result of a line of storms. Cell mode provides a more accurate representation to the extent of the line of thunderstorms.

Radial spread is not necessarily always a bad thing. You can use it to your advantage to distinguish between false or clear air strikes and a real thunderstorm. Most of the strikes of a real storm will be of the typical strike signature and be placed appropriately.

As mentioned above, stronger than average strikes will be painted closer to the airplane. Looking at this in strike mode, a line of these stronger strikes will protrude toward the aircraft.  The result is a stingray-looking appearance to the strikes.    

You can confirm this by clearing the display.  The same stingray pattern should reappear with the tail protruding once again toward the airplane.

Clear Frequently

Clearing the Stormscope display frequently is a must.  How quickly the display “snaps back” will provide you with an indication of the intensity of the storm or line of storms.

You should be sure to give these storms an extra-wide berth.  Clearing the Stormscope in “clear air” will also remove any false strikes that may be displayed allowing you to focus on real cells that may be building in the distance.

Aging

Both ground-based and onboard lightning use a specific symbol to indicate the age of the data.

For Stormscope data shown on the Garmin 430/530, a lightning symbol is displayed for the most recent strikes (first six seconds the symbol is bolded). The symbol changes to a large plus  sign after one minute followed by a small plus  sign for strikes that are at least two minutes old. Finally, it is removed from the display after the strike is three minutes old.

Cells with lots of recent strikes will often contain the most severe updrafts and may not have much of a ground-based radar signature. Cells with lots of older strikes signify steady-state rainfall reaching the surface that may include significant downdrafts. 

Flight Strategy

A nice feature of a Stormscope is that you can quickly assess the convective picture out to 200 nm while still safely on the ground. Same is true for lightning received from the SiriusXM datalink broadcast.

However, for those with lightning from FIS-B, you won’t receive a broadcast until you are well above traffic pattern altitude unless your departure airport has an ADS-B tower on the field.  

As soon as your Stormscope is turned on, within a few minutes you’ll get a pretty good picture of the challenging weather ahead. If you are flying IFR, you may want to negotiate your clearance or initial headings with ATC to steer clear of the areas you are painting on your display. I’ve canceled or delayed a few flights based strictly on the initial Stormscope picture while I was still on the ramp. 

Another goal is to fly as high as allowable. You will benefit from being able to get above the haze layer, and the higher altitude will allow you to see the larger buildups and towering cumulus from a greater distance.

If you are flying IFR and you are continually asking for more than 30 degrees of heading change to get around small cells or significant buildups, then you should call it quits. You are too close, or you are making decisions too late.

Visual or not, the goal is to keep the strikes (in cell mode) out of the 25-mile-range ring on your Stormscope. If one or two strikes pop into this area, don’t worry. Just keep most of the strikes outside of this 25-mile ring.      

Don’t discount the value of a sferics device.  Add one of the data link cockpit weather solutions as a compliment, and you will have a great set of tools to steer clear of convective weather all year long.

The post Is Sferics Equipment Still Needed in the Cockpit? appeared first on FLYING Magazine.

The Atlantic hurricane season officially began June 1 and runs through November 30. While the National Oceanic and Atmospheric Administration (NOAA) has not released its official forecast for 2024 as of this writing, in an average Atlantic hurricane season the U.S. experiences 14 named storms, seven of which are hurricanes and three are major hurricanes.

Buckle up. Given the likely return of La Niña (one of three phases of the El Niño-Southern Oscillation) and record warm sea surface temperatures in February as heated as we see in mid-July, this is not good news if you were hoping for just a mediocre season. If you live and fly anywhere along the Atlantic coastal plain or the Gulf of Mexico, here’s how you can prepare for what may be a wild hurricane season.

Even though hurricane season peaks on September 10, the tropics will begin to see increased activity during the months of June, July, and August as sea surface temperatures increase and the jet stream migrates north into Canada, creating a more favorable breeding ground in the tropics. During this time, what are called tropical waves will develop in the Atlantic Ocean, Gulf of Mexico, and Caribbean Sea, forming in the tropical easterlies (winds moving from east to west). A weak area of low pressure with a closed circulation called a tropical depression may develop along one of these waves.

• READ MORE: The Ins and Outs of Pilot Weather Reports

If conditions are favorable, such as the presence of weak atmospheric wind shear over relatively warm waters, then convection can organize and strengthen into a tropical storm. Once it reaches tropical storm criteria, the National Hurricane Center (NHC) will give the storm a name. The first named storms of 2024 were Alberto and Beryl, with Chris, and Debby to follow. If you recognize a few of these names, be aware that the list is recycled every six years. The NHC points out that a name is removed from the list only “if a storm is so deadly or costly that the future use of its name for a different storm would be inappropriate for reasons of sensitivity.”

Saffir-Simpson Scale

Let’s become familiar with the Saffir-Simpson Hurricane Wind Scale. This scale from 1 to 5 was introduced in the early 1970s by the NHC, using estimates of peak wind, storm surge, and minimum central pressure to describe the destruction from both water and wind for tropical cyclones making landfall.

The Saffir-Simpson scale was simplified in 2010 to be solely determined by a one-minute-average maximum sustained wind at a height of 10 meters (33 feet) above ground level. Once a tropical cyclone reaches hurricane strength (sustained wind speed of 64 knots or greater), it is assigned a category, with a Category 1 hurricane being the weakest and a Category 5 hurricane being the strongest (sustained wind speed of 137 knots or greater). There has been some interesting discussion lately to expand this open-ended scale from 5 to 6 categories given that some of the strongest Category 5 hurricanes are well above that minimum threshold and may not truly capture the potential destruction. This change, however, is unlikely to occur any time soon.

• READ MORE: How to Wrap Your Head Around Weather

Next, you should become familiar with the NHC website, where you will find all of the official guidance published by NOAA. Each named storm, tropical depression, and tropical disturbance will be tracked along with public advisories, such as watches and warnings (e.g., hurricane watch) based on the threat to people and property. You’ll also find a public discussion for the tropics when there are no named storms and a discussion for each system being tracked.

Hurricane Graphics

One product that is ubiquitous during hurricane season is the tropical cyclone forecast cone graphic. This is designed to depict the expected track, location, and strength of the tropical cyclone over the next five days. It also shows the cone of uncertainty.

According to the NHC, “the cone represents the probable track of the center of a tropical cyclone where the entire track can be expected to remain within the cone roughly 60-70 percent of the time.” Of course, the cone tends to get wider with forecast lead time. In other words, there’s more certainty with a forecast that is valid in 48 hours (smaller cone) versus one that is valid in 120 hours (larger cone).

Currently, the graphic only includes those watches and warnings along coastal regions. Starting in 2024, the NHC will be issuing an experimental tropical cyclone forecast cone graphic that also includes inland tropical storm and hurricane watches and warnings in effect for the contiguous U.S. Recommendations from social science research suggest that the addition of inland watches and warnings to the cone graphic will help communicate inland wind risk during tropical cyclone events while not overcomplicating the current version of the graphic with too many data layers.

Electrification of Hurricanes

It’s probably not a surprise to hear that a healthy squall line moving through the Midwest can generate lightning at a rate of more than one strike per second for an extended period of time. But what about in a tropical storm or hurricane? You might be astonished to learn that, on average, a hurricane rarely produces more than a single lightning strike every 10 minutes. While there are some hurricanes and tropical storms that are highly electrified (especially when making landfall), don’t let your guard down—many are not.

No GA pilot is going to fly through the center of a tropical storm or hurricane on purpose. There’s typically plenty of advance warning from the NHC on the location and track of these powerful weather systems. However, once the tropical system makes landfall and weakens, how safe is it to fly through some of the precipitation remnants of the storm? A dissipating tropical system over land can contain some nasty convective turbulence and even small EF0 and EF1 tornadoes. Consequently, it is not unusual for the Storm Prediction Center (SPC) to issue a tornado watch for most tropical systems making landfall.

• READ MORE: Flying Through the Center of a Trough Should Have Been Uneventful

The precipitation signature as depicted on a ground-based radar mosaic associated with tropical cyclone remnants may not look too threatening to the average pilot.

First, it is often void of lightning, unlike what you might see with other convective outbreaks. Also, the automated surface observations in the area may only include +RA for heavy rainfall. In other words, you may not see +TSRA implying lightning exists as well as rain. Second, the ground-based radar mosaic may not have much of a true cellular structure with high reflectivity gradients that we often see with other deep, moist convection.

Despite the lack of lightning and a relatively benign-looking radar image, tropical system remnants should be treated as if they were that intense squall line in the Midwest. After such a tropical system makes landfall and begins to rapidly dissipate into a tropical depression or extra-tropical cyclone, it will move inland carrying similar risks.

This is evidenced by the remnants of Hurricane Katrina in 2005. This was a powerful storm that made landfall as a strong Category 3 hurricane at the end of August near New Orleans and moved north into the Tennessee and Ohio valleys as it dissipated.

Even after the storm was declared as extra-tropical, tornado watches were issued just to the east of Katrina’s track along the central and southern Appalachian Mountains and into the Mid-Atlantic. It is important to understand that the lack of lightning does not imply the lack of dangerous convective turbulence.

In order for lightning to form within deep, moist convection, three ingredients must be present in the right location of the cloud. This includes ice crystals, supercooled liquid water, and a “soft hail” particle called graupel.

Updrafts in tropical systems are actually quite limited, usually no more than 1,500 feet per minute. These updrafts are far from upright, owing to the strong horizontal wind shear present. According to hurricane researcher Dr. Robert Black, “while there is some presence of electrical fields, the graupel-liquid water-ice combination turns out to be at the wrong place at the wrong temperature and in insufficient volume to give the spatial charge distribution to produce a lightning discharge.”

In layman’s terms, little supercooled liquid water gets carried high enough to the level necessary to electrify the cloud. This continues to be true even after the tropical system makes landfall and dissipates inland.

The most serious electrification occurs in the outer rain bands as they spiral outward from the center of the storm. These can often look a lot like that Midwest frontal convection. Most convective cells along that squall line in the Great Plains or Midwest often move in a northeasterly direction based on the shift of the air mass and the winds aloft.

However, this may not be the case for these tropical cyclone bands. You may find these cells moving in a northerly or even westerly motion depending on the track of the tropical system.

Remain Outside of the Northeast Quadrant

If you split the storm into four quadrants based on its forward movement, the most intense atmospheric shear occurs in the northeast quadrant. This is typically where you will find the highest storm surge at landfall and where tornado watches are usually issued. As the system makes landfall, moves inland, dissipates, and becomes extra-tropical, you will find the northeast quadrant should be strictly avoided.

As we make our way through hurricane season this year, keep a close eye on the tropics and heed the guidance from the NHC. Even weak storms making landfall can add significant hazards for most aircraft. The convection associated with these storms is not the normal kind we experience during the warm season. Therefore, you can’t assume that the same ground-based signatures you might steer away from with normal convection will be present with this tropical convection.

Last, but not least, don’t use the lack of lightning to be your guide to determine what precipitation is safe to fly through. Assume there is ample wind shear in the atmosphere regardless of how it appears on radar. It may prove not to be a fair match for your aircraft or skill set.

This feature first appeared in the May 2024/Issue 948 of FLYING’s print edition.

The post Keeping an Eye on the Storm appeared first on FLYING Magazine.

Answer: In general aviation, one of the most cumbersome things to do while in flight is to file a pilot weather report, more commonly known as a PIREP. This has created the unfortunate situation that on any given day 98 percent of the PIREPs in the system are typically describing weather conditions at or above 18,000 feet.

It wasn’t all that long ago that the Enroute Flight Advisory Service (EFAS) was available primarily for pilots to receive weather updates while they were flying to their destination. More importantly, EFAS was the main outlet to file a PIREP such that it was guaranteed to be input into the system and become available for other pilots to see. This service was also called Flight Watch.

Given that EFAS was organized by Air Route Traffic Control Centers (ARTCC), you simply put 122.0 MHz into your radio, keyed the mic, and referenced them by a particular center’s airspace you were located within. For example, if you were in the Jacksonville Center’s airspace in Florida, your initial call might have been, “Jacksonville Flight Watch, Skyhawk One Two Three Whiskey X-ray, 30 miles southwest of the Brunswick V-O-R at five thousand five hundred.” Then as long as you were more than 5,000 feet above the ground, someone from Flight Watch came on the frequency, and you engaged in a two-way conversation to file your PIREP.

• READ MORE: The Ins and Outs of Pilot Weather Reports

However, EFAS was terminated on October 1, 2015. This now leaves the arduous task of finding the right Flight Service Station (FSS) frequency, making contact, and hoping someone on the other end responds to your call. The frequency you use to transmit and receive is dependent on your location. Pull out your VFR sectional (paper or electronic version), find the nearest VOR to your location, and look for the frequency located on the top of the VOR information box.

Of course, the correct frequency to use may also be available through your avionics or one of the many heavyweight electronic flight bag apps.

This is the frequency you will use to transmit and receive. Below the box is the name of the particular FSS to use in your initial call. For example, if you are near the Brunswick VORTAC in Georgia, your initial call may be, “Macon Radio, Skyhawk One Two Three Whiskey X-ray, transmitting and receiving on 122.2, over.” This is the easy case.

• READ MORE: How to Wrap Your Head Around Weather

If there’s an “R” shown at the end of the frequency (e.g., 122.1R), then that means FSS will receive on this frequency and you will transmit on this frequency. And you’ll need to be sure you listen for its response over the VOR frequency. Make sure your volume is turned up and not muted on your VOR radio.

This column first appeared in the May 2024/Issue 948 of FLYING’s print edition.

The post How Do I File a Pilot Weather Report Online? appeared first on FLYING Magazine.

Pilot weather reports, more simply known as PIREPs, are those rare commodities that general aviation pilots yearn for during preflight planning or while en route using datalink weather. They are vital since they answer these basic questions: At what altitude will I likely encounter ice? What is the severity of those icing conditions? What is the severity of turbulence at my planned altitude? And the most frequently asked question: What altitude will I find the cloud tops?

Perhaps there’s a PIREP or two out there that might just fill the void and answer one or more of these basic questions.

Other Consumers of PIREPs

It’s important to know that pilots are not the exclusive consumers of your reports. Meteorologists, air traffic controllers, dispatchers, briefers, and researchers are all extremely interested in your PIREPs. On a visit to the Aviation Weather Center (AWC) in Kansas City,

Missouri, nearly two decades ago, I asked one of the forecasters if PIREPs were important to him. He responded without hesitation, “Oh, god, yes!” as if his job depended on it. While he could continue to do his job without PIREPs, a forecaster can do his job better with more of them in the system.

Some meteorologists that issue terminal aerodrome forecasts (TAFs) examine the latest PIREPs before constructing their forecast. By far, the forecasters that depend on PIREPs the most are those located at the Center Weather Service Units (CWSUs) and those at the AWC. Let’s say an urgent pilot weather report from a Boeing 767 comes in for severe icing. An audible alarm will sound on the forecaster’s terminal at the AWC alerting them to the urgent report. They must click the alarm to silence it. AWC forecasters affectionately call this the “blue light special” since the alarm button turns that color.

• READ MORE: How to Wrap Your Head Around Weather

Such a PIREP will likely trigger the AWC meteorologist to pick up their “bat phone” and start a conversation with a CWSU meteorologist. They put their heads together to determine if there’s a need for a SIGMET or perhaps just a simple center weather advisory (CWA). The goal is to avoid advisories that may conflict and create confusion for pilots, although it does happen from time to time, especially when the weather is rather extreme.

As such, SIGMET advisories for severe or extreme turbulence and severe icing literally live and die by PIREPs. An urgent PIREP (UUA) of severe icing or severe or extreme turbulence may trigger an AWC forecaster to issue a SIGMET based solely on the conditions reported by a single pilot or aircrew. In fact, if you read the SIGMET or CWA text carefully, you will likely notice it often says, “RPTD BY ACFT” or “RPTD BY B767,” which tells you the SIGMET was issued due to one or more PIREPs of severe conditions.

At the other extreme, the AWC forecaster may cancel a SIGMET because there are no longer reports of severe icing or turbulence in the area. It may just be mostly moderate reports. Again, the decision to let the SIGMET die or extend it largely comes from PIREPs.

There’s nothing inherently wrong with a forecaster issuing a SIGMET without pilots reporting severe conditions. However, many forecasters want to see “ground truth” before issuing one. This is because issuing a SIGMET for severe ice, for example, makes the area a no-fly zone for most GA aircraft. Your TBM 960 can no longer legally fly through this area since it is not certified for flight into severe icing conditions. The FAA will no doubt pull the SIGMET as evidence that you should have known better if you turn yourself into a flying popsicle and need assistance.

Automation Ingests Your PIREPs

Your PIREPs are incorporated by weather guidance such as the Current Icing Product (CIP) and Graphical Turbulence Guidance (GTG) product found on aviationweather.gov. Both of these use PIREPs for icing and turbulence, respectively, to build the product’s analysis.

For example, a positive icing report helps CIP to increase the confidence there’s icing at the altitude reported by the pilot at the time the guidance is valid. Conversely, if the report is for negative icing, it might decrease the icing probability at that altitude.

But don’t try to fool the algorithm. If you were to report moderate ice in an area where the sky is obviously clear, it will be able to toss out your bogus report since it also relies on other observational data, such as satellite and surface observations (METARs). Sure, it’s unlikely any pilot would file a bogus report on purpose, but at times turbulence PIREPs are miscoded as reports for icing or the VOR identifier provided in the report for the location is miscoded (e.g., ODG instead of OGD).

Filing That Report

If you are like me, you undoubtedly find it difficult to file a pilot weather report. This is especially true when flying in busy terminal airspace, where it often matters the most. Whether flying IFR or VFR with flight following, it’s a challenge.

First, you need to leave the frequency. That involves asking the controller permission to switch frequencies so you can make that call to flight service. Once you’ve received permission, then you have the chore of finding the correct frequency and hoping someone on the other end will answer. When the weather is challenging, expect to hear, “N1234B, you are number four, standby.”

• READ MORE: Flying Through the Center of a Trough Should Have Been Uneventful

Can you just give the controller your PIREP and skip the call to flight service? Sure, but the controller’s primary job is not to file your report—it is to separate IFR aircraft from other IFR or special VFR aircraft.

In other words, there’s no requirement for that controller to take your report and forward the details to flight service so the rest of the stakeholders in the aviation industry can take advantage of it. If you are reporting severe conditions, such as severe or extreme turbulence, severe ice, or low-level wind shear, the controller should be passing this along. However, in busy airspace, the controller may just say, “Thanks!” and that’s as far as it goes.

If you are lucky enough to have an internet connection in the cockpit, there are resources to file the report online. You may find that some of the heavyweight apps provide this service. There is one such portal on the aviationweather.gov website.

Just be aware that you have to create an account and then make direct contact to provide your name, airman’s certificate number, and specific affiliation (e.g., airline, flight school, government, military, etc.) for validation purposes. Once this validation is complete, you can sign in and file a report directly online. Those reports are appended with “AWCWEB” in the remarks like this one:

OVE UA /OV KCIC/TM 1515/FL260/TP B737/TB MOD/RM 180-260 AWC-WEB

However, to make the process even easier, download the Virga app (search for “Fly Virga” in the App Store or Google Play Store). This is a great option since it is fully integrated with the aviationweawther.gov PIREP portal. Visit www.flyvirga.com for more information. Note that you still must have a Wi-Fi or cellular connection to file the report.

When making a PIREP, be sure to be specific. Avoid general terms, such as “icing during the climb” or “turbulence during descent,” unless you specify the altitudes you experienced icing or turbulence in the climb or descent. This is critical since nobody knows what altitude you climbed to or descended from. Moreover, the CIP and GTG analyses depend on these specifics in order to utilize your report effectively.

Also, for turbulence reports, add details such as whether or not you were in or outside of the cloud boundary. This is to differentiate turbulence related to convection (i.e., cumuliform-type clouds) versus clear air turbulence.

Age Makes a Difference

How long is a PIREP useful? While it’s difficult to pick out a particular length of time, reports of icing conditions more than 75 minutes old are typically useless to a pilot and to the CIP algorithm. Not unlike thunderstorms, icing conditions and intensity can change rapidly in time and space. Precipitation and clouds come and go as the synoptic, or big weather picture, changes. Clouds become supercooled due to rapid cold-air advection, and other clouds become glaciated (all ice crystals) as temperatures fall below minus-20 degrees Celsius.

• READ MORE: Go or Stay? Getting Personal with Your Pilot Minimums

From an aging perspective, turbulence PIREPs have an even shorter shelf life than icing PIREPs. Turbulence is highly transitory. An eddy of air might be propagating to a lower altitude after a pilot encounters it. Twenty minutes later, the next pilot at that same altitude may not see any bumps since the cause of the turbulence is now at a lower altitude. Again, it’s hard to agree on a specific time, but after about 45 minutes an isolated report of severe turbulence is probably too old to trust.

Required PIREPs

According to 14 CFR § 91.183 (b), a pilot flying under IFR in controlled airspace must report “any unforecast weather conditions encountered” by radio to ATC. Given this broad-brush regulation, you should limit your report to any forecast errors strictly significant to aviation operations. Unless it is urgent, there’s no need to make a big deal out of it either.

For example, let’s say you depart an uncontrolled field that has a TAF issued, and the forecast suggests that ceilings will be 2,000 feet at the departure time. As you climb out, you penetrate the lowest cloud deck at 900 feet AGL—this is significant to aviation, and you should report it to ATC. “Cirrus 1WX, one thousand two hundred, climbing four thousand, ceiling niner hundred overcast” is all you need to say.

While ATC may make use of this report for its own purposes, it is highly unlikely it will assemble your report into an official PIREP. To be sure this is relayed to the rest of us inquiring pilots, take a moment to file that report with flight service when you have the time.

Catch-22?

One of the comments I repeatedly hear from pilots is, “If I report icing, won’t I be admitting guilt if I’m piloting an aircraft not certified for flight into known icing conditions?” I’m not an attorney, however, I believe the answer is yes and no.

There was a similar concern from pilots when cockpit voice recorders (CVRs) were first introduced. Could the FAA use the recording against a pilot? The FAA said that wasn’t the intention, and CVRs were strictly added to improve safety of flight to learn why mistakes are made—not to bust the pilot during some random audit.

Similarly, there are no PIREP police waiting to nab you at the FBO in random fashion. Now, if you reported icing conditions and then had a hard landing that caused a prop strike due to a load of ice on the airframe, it’s likely the FAA will use your own PIREP against you.

Controllers are there to help you out of a bad situation. As always, confess to them that you are quickly becoming a flying popsicle. Be assertive with your request— tell them exactly what you need. For example, “1WX is in moderate icing and needs an immediate descent to four thousand.” If necessary, don’t hesitate to declare an emergency because doing so will likely get you priority handling.

Just remember that PIREPs are not just a private conversation between you and flight service. They are broadcast to the world. So, try to challenge yourself on each and every flight to file at least one PIREP.

So it doesn’t matter if the weather is extremely challenging or “oh-so boring.” Sometimes the best report is one that states smooth conditions and negative icing. There may be a pilot out there getting their back fillings jarred, and your report of glassy smooth conditions just 2,000 feet above them will help make their flight more enjoyable.

The hardworking folks at the AWC only complain when they don’t get enough PIREPs. So, let’s file those reports and not give them a reason to complain. I can tell you from firsthand experience, there’s nothing worse than a whiny meteorologist.

This column first appeared in the April 2024/Issue 947 of FLYING’s print edition.

The post The Ins and Outs of Pilot Weather Reports appeared first on FLYING Magazine.

Northrop Grumman, I needed something that would challenge my mind, body, and spirit. There were two options on the table. I had just graduated with my master’s degree and was seriously thinking of taking the next leap of faith and earning a doctorate.

But that was quickly overshadowed by my second option—my childhood dream of learning to fly. And I wasn’t disappointed. It did challenge my mind, body, and spirit every step of the way.

What intrigued me the most about learning to fly was that it required mastering many disciplines. In other words, it’s more than just jumping into an airplane and learning stick-and-rudder skills. You have to become entrenched in subjects such as aerodynamics, radio navigation, geography, radio communications, airspace, map reading, legal, medical, and my favorite discipline, meteorology.

Despite my background as a research meteorologist, my aviation weather background was limited when I was a student pilot. So, I was very excited to discover what more I might learn about weather in addition to all of these other disciplines. If you are a student pilot, here are some tips that will help you achieve a good foundation with respect to weather.

It Isn’t Easy

First and foremost, weather is inherently difficult. It’s likely the most difficult discipline to master because of the uncertainty and complexity it brings to the table. Therefore, strive to understand what basic weather reports and forecasts the FAA effectively requires that you examine before every flight. It certainly doesn’t hide it. It’s a fairly short and succinct list that’s all documented in the new Aviation Weather Handbook (FAA-H-8083-28) and the Aeronautical Information Manual (AIM). Ultimately, knowing the nuts and bolts of this official weather guidance will help with your knowledge and practical tests and give you a head start once the ink is dry on your private pilot certificate.

Second, as a student pilot, plan to get your weather guidance from a single and reliable source. Try not to bounce around using multiple sites or apps. There are literally hundreds, if not thousands, of websites and apps that will deliver weather guidance to your fingertips such that you can become overwhelmed with all of the choices, and entropy quickly takes over. Besides, flight instructors love to show off their unique collection of weather apps on their iPhone. Sticking with the official subset of weather guidance will allow you to focus on what matters the most.

• READ MORE: Aviation Weather Center Website Upgrade—the Good, Bad, and Ugly

Once you receive your private certificate, then you can expand the weather guidance you use to include other websites and apps.

The two internet sources that should be at the top of your list include the Aviation Weather Center (aviationweather.gov) and Leidos (1800wxbrief.com). Both of these sites provide the essential weather guidance needed to make a preflight weather decision. Using one or both of these sites will help focus you on the official weather guidance the FAA demands you use.

Categorize Your Data

Third, when you look at the latest weather guidance, take a minute and characterize each product. It should fall into one of three categories: observational data, advisories, or forecasts. Knowing its category will tell you how to properly utilize that guidance. For example, if you come across a visible satellite image, that’s an example of observational data.

Observational data is always valid in the past and typically comes from sensors. What about a ground-based radar mosaic (e.g., NEXRAD)? That’s also an observation. Pilot weather reports (PIREPs) and routine surface observations (METARs) are also considered observational data. While not a pure observation, the latest surface analysis chart that is valid in the recent past will identify the major players driving the current weather systems.

• READ MORE: What Is the Criteria for Issuing a Convective SIGMET?

Observations are like the foundation when building a house. All other weather guidance you use will build on that foundation. A sturdy and well-built foundation is the key to a good preflight weather briefing. You can’t know where the weather is going until you know where it has been. Identifying the latest trends in the weather through the use of these observations is the cornerstone of this foundation. When possible, looping the guidance over time will expose these trends. Is the weather moving or stagnant? Is it strengthening or weakening over time?

Advisories such as the initial graphical AIRMETs (G-AIRMETs) snapshot, SIGMETs, and center weather advisories (CWAs) are the front lines of aviation weather. They are designed to highlight the current location of the truly ugly weather. Advisories build the structure that sits atop of this foundation. Essentially, these advisories summarize the observational data by organizing it into distinct hazards and areas of adverse weather to be avoided.

Forecasts are the springboard for how these observations and advisories will evolve over time. You can think of forecasts as the elements that protect the finished house, such as paint, shingles, and waterproofing. This also includes the alarm and surveillance system to alert you to the possible adverse weather scenarios that may occur during your flight. While forecasts are imperfect, they are still incredibly useful. Forecasts include terminal aerodrome forecasts (TAFs), convective outlooks, prog charts, and the remaining four snapshots for G-AIRMETs.

Dive into the Details…

Fourth, details matter quite a bit. Look at the guidance and identify what stands out. Don’t make a decision too early. Instead, carefully observe and gather facts. Is the precipitation occurring along the route limiting the ceiling and/or visibility? Is the precipitation expected to be showery? This is a clear indication of a convective process in place.

Are the surface observations reporting two or three mid- or low-level cloud layers? Again, this is another indication of a convective environment. This can be especially important to identify, especially when there’s a risk of thunderstorms that have yet to form.

…But Fall Back on the Big Picture

Fifth, get a sense of the big weather picture. This is likely the most difficult aspect of learning how to truly read the weather. Think about the big weather picture as the blueprint for building an entire community. It’s what brings everything together. When I do my own preflight briefings, my decisions are largely driven by what’s happening at that synoptic level.

Lastly, read, read, and read some more. Focus mostly on the weather guidance and less on weather theory. These are the specific weather products mentioned earlier. Weather theory is something you can tackle at a later time. The FAA’s Aviation Weather Handbook is a great start. You can download a PDF document for free from the agency website and add this to your online library. This was issued in 2022 to consolidate the weather information from six FAA advisory circulars (ACs) into one source document. My book, Pilot Weather: From Solo to the Airlines, was published in 2018 and is written for pilots at all experience levels in their journey to learn more about weather.

If you fly enough, you will eventually find yourself in challenging weather. The goal of any preflight weather briefing is to limit your exposure to adverse conditions, and that takes resources and time. Once you’ve mastered the weather guidance, then giving Flight Service a call at 1-800-WXBRIEF will allow you to sound like a true professional.

Yes, I eventually did earn that doctorate, but I am really happy that I took the step over 25 years ago to learn to fly. One guarantee with weather: You can never learn enough. I am still learning today.

This column first appeared in the March 2024/Issue 946 of FLYING’s print edition.

The post How to Wrap Your Head Around Weather appeared first on FLYING Magazine.

Answer: When looking at the surface analysis chart issued every three hours by meteorologists at the Weather Prediction Center (WPC), you may have seen a tan dashed line with a label “OUTFLOW BNDRY” nearby. This is what meteorologists call a convective outflow boundary.

You may view North American surface analysis here.

Convective outflow boundaries emanating away from thunderstorms are generated as cold, dense air descends in downdrafts then moves outward away from the convection to produce a mesoscale cold front also known as a “gust front.” 

• READ MORE: Should I File an Initial Approach Fix?

Some gust fronts can be completely harmless or may be a precursor for an encounter with severe turbulence and dangerous low-level convective wind shear. The direction of movement of the gust front isn’t always coincident with the general motion of the thunderstorms. If the gust front is moving in advance of the convection, it should be strictly avoided. The pilot’s best defense is to recognize and characterize the gust front using METARs, ground-based radar, and visible satellite imagery.

According to research meteorologist and thunderstorm expert Charles Doswell, “cold, stable air is the ‘exhaust’ of deep, moist convection descending in downdrafts and then spreading outward like pancake batter poured on a griddle.” 

As a pulse-type thunderstorm reaches a point where its updraft can no longer support the load of precipitation that has accumulated inside, the precipitation load collapses down through the original updraft area. Evaporation of some of the rain cools the downdraft, making it even more dense compared to the surrounding air. When the downdraft reaches the ground, it is deflected laterally and spreads out almost uniformly in all directions, producing a gust front.

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Gust fronts are normally seen moving away from weakening thunderstorm cores. Once a gust front forms and moves away from the convection, the boundary may be detected on the NWS WSR-88D NEXRAD Doppler radar as a bow-shaped line of low reflectivity returns usually 20 dBZ or less. Outflow boundaries are low-level events and do not necessarily produce precipitation. Instead, the radar is detecting the density discontinuity of the boundary itself along with any dust, insects, and other debris that may be carried along with the strong winds within the outflow. The gust front in southwest Missouri shows up very well on the NWS radar image out of Springfield as shown below.

An important observation is to note the motion of the gust front relative to the motion of the convection. In this particular case, the boundary is steadily moving south while the thunderstorm cells that produced the gust front are moving to the east. This kind of outflow boundary is usually benign, especially as it gains distance from the source convection. On the other hand, a gust front that is moving in the same general direction in advance of the convection is of the most concern. These gust fronts often contain severe or extreme turbulence, strong and gusty straight-line winds, and low-level convective wind shear.

As mentioned previously, gust fronts are strictly low-level events. As such, even the lowest elevation angle of the radar may overshoot the boundary if it is not close to the radar site. 

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Shown below at 22Z, the NWS WSR-88D NEXRAD Doppler radar out of Greenville-Spartanburg, South Carolina, is the closest radar site and clearly “sees” the gust front (right image). However, the NEXRAD Doppler radar out of Columbia, South Carolina (left image), is farther away and misses the gust front completely. As the gust front moves away from the radar site, it may appear to dissipate, when in fact, the lowest elevation beam of the radar is simply overshooting the boundary. As a result, it is important to examine the NEXRAD radar mosaic image before looking at the individual radar sites.

Not all gust fronts are easy to distinguish on visible satellite imagery; the gust front could be embedded in other dense clouds, or a high cirrus deck may obscure it. It is also possible that the boundary may not have enough lift or moisture to produce clouds. In many cases, however, it will clearly stand out on the visible satellite image. When the gust front contains enough moisture, as it was in this situation, cumuliform clouds may form along the boundary and move outward as can be seen in this visible image below centered on Charlotte, North Carolina. This is very common in the Southeast and coastal regions along the Gulf of Mexico given the higher moisture content. 

As this particular gust front passed through my neighborhood located south of Charlotte, strong, gusty northerly winds persisted for about 10 minutes. As is common, the main core of the precipitation didn’t start to fall for another 10 minutes. When a gust front such as this appears on satellite or radar, it is important to monitor the METARs and ASOS or AWOS closely for the occurrence of high winds. Several airports in the vicinity reported wind gusts peaking at 30 knots. The sky cover went from being just a few scattered clouds to a broken sky with these cumuliform clouds shown below moving rapidly through the region.

These cumuliform-type clouds were the result of a strong convective outflow boundary that moved through Fort Mill, South Carolina.  [Courtesy: Scott Dennstaedt]

As mentioned earlier, a gust front moving away from thunderstorms is a low-level event that can contain strong updrafts and downdrafts. The graph shown below is a time series, plotting the upward and downward motion or vertical velocity in a strong gust front as it moves over a particular point on the ground. 

The top half of the graph is upward motion and the bottom half is downward motion. Time increases from left to right. As the gust front approaches, the vertical velocity of the air upward increases quickly over a one- or two-minute period. While the maximum vertical velocities vary with height in the outflow, a common maximum number seen is 10 meters per second (m/s) at about 1.4 kilometers or 4,500 feet agl (25 knots is roughly 12 m/s for reference). 

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As the gust front moves through, the velocities abruptly switch from an upward to a downward motion, creating strong wind gusts at the surface. Most outflow boundaries don’t extend above about 2 kilometers or 6,500 feet agl. What is remarkable is that upward-to-downward motion changes in just about 30 seconds over the ground point where this was observed. But imagine flying an aircraft at 150 knots through this— the up-and-down exchange will happen in just a few seconds, producing a jarring turbulence event.

Just in case you were wondering, gust fronts are conveniently filtered out by your datalink weather broadcasts as shown below for XM-delivered satellite weather. This is because the broadcast only provides returns from actual areas of precipitation. Often outflow boundaries or gust fronts produce low reflectivity returns that fall below the threshold used to filter out other clutter not associated with actual areas of precipitation. 

When in flight, pay particular attention to surface observations, looking for strong, gusty winds, before attempting a landing at an airport when storms are approaching. 

The post What Is an Outflow Boundary Shown on a Surface Analysis Chart? appeared first on FLYING Magazine.