ForeFlight 10.3 is available now for download on the App Store. This release includes 200+ refinements and performance enhancements, with a couple nice touches like a Runway Final Approach Alert and Logbook – Track Log links.
With the first half of 2018 (and Oshkosh) behind us, we decided to take a short break from major feature additions and focus instead on improvements, refinements, and fixes. Each team found ways to optimize their respective piece of the app, increasing speed, reducing processor and memory usage, conserving battery, and improving overall app performance. The result is over 200 behind-the-scenes changes that will keep ForeFlight running smoothly so we can get back to doing what we love most – building awesome features that make flying easier, safer, and more enjoyable.
Runway Final Approach Alert
ForeFlight Runway Final Approach Alert
The new alert provides added situational awareness on final approach by calling out the runway name and your distance from it. The alert triggers for any runway that you are approaching based on your altitude, vertical speed, track, and distance from the runway threshold. The Runway Final Approach Alert is available for all subscribers in More > Settings > Alerts.
Logbook – Track Log Links
Top: Logbook link to the associated Track Log. Bottom: Link to the Track Log connected to the Logbook entry.
Logbook entries and recorded Track Logs that are associated with each other now include links to view the details of the other, making it easier to tie them to the same flight. The link is automatically created when the Track Log auto-record and Logbook auto-log settings are enabled, but you can also use the Send To > Logbook option when viewing a Track Log to manually link the two. Track Logs associated with multiple Logbook entries show the number of linked entries, so you can see if you’ve already created a Logbook entry from a given Track Log.
New Airport Resources
New Airport Information Resource Links
The list of miscellaneous airport details in Airports > More > Features or in the airport popup on Maps now includes links to view the airport in the Apple Maps app or the airport’s Wikipedia page.
Be sure to visit our video library for additional support and information.
This week Team ForeFlight heads to the second annual FLYING Aviation Expo in Palm Springs, California. Janessa and Thomas will be on hand in the ForeFlight booth (#715), ready to demonstrate all of the latest ForeFlight features, offer tips and tricks to make you a ForeFlight super-user, and answer any how-to questions you may have.
Thomas is presenting our ForeFlight 201—Advanced Flying with ForeFlight seminar each day of the show. This presentation is an advanced, scenario-based course and you will learn how to use the app to its fullest from planning to inflight navigation.
ForeFlight 201 Seminar Schedule:
Thursday, October 15 at 4:00pm in Room Primrose A
Friday, October 16 at 10:00am in Room Primrose A
Saturday, October 17 at 11:30am in Room Primrose A
It’s early in the morning and you’re preparing to depart on an IFR flight out of Asheville (KAVL) in western North Carolina. While finishing your breakfast you open up the ForeFlight Mobile app, insert your favorite route to your destination and tap the little suitcase to pack all of the current charts, NOTAMs, fuel prices and latest weather for your flight. While ForeFlight is packing everything that you need (love that feature!), you decide to take a peek at the latest terminal forecast for Asheville (below) and see something that doesn’t look too appealing – WS020/07040KT; ForeFlight translates this initial part of the TAF to a forecast for wind shear. Ugh!
A terminal forecast for non-convective low-level wind shear (LLWS) as shown in ForeFlight.
So you tap on the Imagery tab and select the Graphical AIRMETs collection and see under Tango a forecast for low-level wind shear (LLWS) covering a large area from the panhandle of Maryland southwest to northern Georgia as shown below. This area impacts a good portion of your proposed route including your departure out of Asheville. Now what? Cancel the flight since you don’t want to be fooling around with wind shear in the mountains? Perhaps, but let’s take a closer look at this particular forecast and what it really means.
A forecast for non-convective low-level wind shear (LLWS) issued by the Aviation Weather Center in the form of a Graphical AIRMET (G-AIRMET). The actual magnitude of the wind shear or direction is not provided in the G-AIRMET.
Both of these forecasts identify the potential for non-convective low-level wind shear (LLWS). This is perhaps the most misunderstood weather forecasts in aviation. Pilots hear the term wind shear and immediately equate this to severe turbulence. It is not a forecast for turbulence per se and is definitely not the same wind shear you might experience in and around areas of convection since it has nothing to do with thunderstorms. So now that we know what it is not, let’s dig a bit deeper.
Wind shear is defined as a marked change of wind speed and/or wind direction over a horizontal plane or within a vertical depth of the atmosphere. When the wind shear occurs near the surface, it is referred to as low-level wind shear and abbreviated LLWS. Non-convective LLWS as it appears in a TAF or within AIRMET Tango (also G-AIRMETs) is primarily a form of vertical speed shear. That is, the wind is forecast to rapidly increase with height within the wind shear layer. In addition, winds may also change direction with increasing altitude within the wind shear layer – although it is primarily a forecast for a change in wind speed.
Here’s the pertinent part of the coded Asheville TAF shown above:
01008KT 6SM -SHRA BR OVC015 WS020/07040KT
Decoded, this TAF suggests that between 1200 and 1600 UTC the surface winds will be 010 degrees (true) at 8 knots with a visibility of 6 statute miles with light rain showers and mist and an overcast ceiling of 1,500 feet. Easy so far? Now the confusing part. The WS code following all of this translates to non-convective low-level wind shear. The 020 following the WS code defines the depth of the wind shear layer which is 2,000 feet above ground level (AGL) in this case. Two thousand feet is the maximum depth forecast, but you may also see 005 (500 feet), 010 (1,000 ft) or 015 (1,500 ft). But it’s also acceptable to see 018 representing an 1,800 ft depth to the wind shear layer.
The remainder of the code following the forward slash defines the wind speed and direction at the top of the wind shear layer. Therefore, 07040KT translates to a wind direction of 070 degrees (true) at 40 knots at 2,000 feet AGL. Putting it all together, the winds are expected to increase rapidly from 8 knots at the surface to 40 knots at 2,000 feet AGL. This forecast also implies that winds will also shift direction from 010 degrees at the surface to 070 degrees at 2,000 feet although there’s no way to know how or where the shift occurs within the wind shear layer. Now that you are an expert decoder of the wind shear forecast in a TAF, what does it mean to you as a pilot?
As mentioned earlier, this is not a forecast for severe turbulence as many pilots might have been taught. Forecast or not, it is a common phenomenon and you may have flown through it and did not even know it was there. In fact, in the evening and overnight hours a nocturnal temperature inversion is often the catalyst for non-convective LLWS to evolve. In the nocturnal flavor of non-convective LLWS, the sky is often clear and the winds at the surface are usually light or calm. But the air in the wind shear layer remains glassy smooth. The only thing you may notice is a change of groundspeed as you penetrate the layer.
Essentially, non-convective LLWS is a river of faster flowing air just above the surface whether it occurs during the day or night. More often than not, a surface-based temperature inversion is present and as mentioned above is the primary catalyst for this form of wind shear. Normally the temperature decreases with increasing altitude. However, with an inversion the temperature actually increases with height through some depth. Meteorologists call this a negative lapse rate. The more negative the lapse rate, the more stable the atmosphere. A stable atmosphere resists or inhibits upward or downward motion keeping the potential wind shear layer near the surface from mixing. No mixing yields no turbulence.
Profile view from the ILS approach to runway 7 at Rockford, Illinois.
Beware on approach
Even though the air may be glassy smooth, imagine the case where you are flying an instrument approach with this kind of wind shear in place. Even if the wind doesn’t change direction in the wind shear layer, you will still have to contend with the change of wind speed that is increasing rapidly with height from the surface. If the wind is right off your nose and you are flying an ILS, for example, you will notice as you intercept the localizer around 2,000 ft AGL your groundspeed will be abnormally low (you have a 40 knot headwind in the case for Asheville). As you begin to track the glideslope, your groundspeed will increase since the headwind is decreasing in the descent. This means you’ll have to increase your rate of descent to keep the glideslope needle centered.
You can also imagine this being a tailwind or a direct crosswind while on the approach. So you have be constantly changing the descent rate or heading (crab angle) into the wind. Keep in mind that non-convective LLWS comes in all shapes and sizes. There’s not a one size fits all method to handle this. In most cases, this form of wind shear is not something you should fear, but it’s something you definitely need to manage. It is probably present more than it’s forecast.
Besides the shear in the overnight hours discussed above, non-convective LLWS may be associated with the following: frontal passage, lee side mountain effect, sea breeze front and Santa Ana winds just to name a few. In a future blog I will discuss the meteorology behind non-convective LLWS and provide some background when this phenomenon can become dangerous.
As the old saying goes, in so many ways, a picture speaks a thousand words. By now you have probably seen the chilling photo like the one shown in this media report of Delta Flight 1889 parked safely at the gate after diverting to Denver International Airport. This was the result of a nasty encounter with hail at 34,000 feet while en route from Boston to Salt Lake City last Friday evening. It makes little sense with today’s proven technology that any commercial aircraft should ever encounter such a hazardous situation and risk the lives of those on board. The crew of this Airbus A320 did an admirable job getting the aircraft safely on the ground after this encounter, but there’s another side to the story that got them into trouble in the first place. A few simple pictures in the cockpit may have made all the difference in the world to avoid putting these passengers through such a harrowing experience.
It’s truly a shame that a pilot flying a single engine Cessna 172 can have significantly more weather information available to them in the cockpit than the crew of this A320 had. We woulda, coulda, shoulda this crew’s decision to fly into this developing area of convection, but that’s not the point. The simple fact is, aircrews flying paying customers today are not equipped with matured technology that will provide them with valuable weather data to make timely decisions during any phase of flight to avoid these kinds of encounters.
Think big picture
Sure, these aircraft are equipped with onboard radar and the crews they carry are highly trained and experienced pilots who know how to make use of that radar. Even when properly used, onboard radar has limitations. It is a real-time snapshot of what’s occurring right now out in front of the aircraft, and this is critical data for tactical decisions, but is simply a microcosm of the overall energy in the atmosphere. In events like this, it is the macro picture of what’s unfolding 100 or more miles away that is often just as important. This large-scale view is better suited to help make the proper strategic decisions, especially when it comes to a developing area of severe thunderstorms. But that information needs to get to the pilot-in-command.
The view from above
Air crews can and do get help from air traffic controllers. Controllers can tout about a “hole” that the last five aircraft recently traversed. But that doesn’t necessarily tell you how fast that hole is closing up and whether or not it will still be there when you arrive. The crew may also have access to their company’s dispatchers, but in the end, the captain may not have the complete picture in his or her head…and that’s where these strategic decisions are made.
This color-enhanced infrared satellite image (also available in ForeFlight Mobile) valid at 0045 UTC shows two distinct areas of convection. Dark purple and white areas denote very cold cloud tops likely from strong updrafts. Flight path of Delta 1889 taken from Flightaware is shown in black.
The squeeze play
Even before Delta Flight 1889 departed Boston’s Logan Airport, two areas of convection started to blossom in Colorado, one in northeast Colorado and the other in southeast Colorado. At 0045 UTC, you can see two distinct systems on the color-enhanced infrared satellite image shown above. As the Airbus crossed over the Mississippi River (black line is the aircraft’s approximate track taken from Flightaware) around the time this satellite image was taken, both areas of thunderstorms had been designated as severe. Nevertheless, there’s clearly a gap between these two convective systems and that appears to be where the crew was headed.
This color-enhanced infrared satellite image valid at 0115 UTC shows the gap between these two areas of convection beginning to quickly fill in with a rapidly developing line of severe thunderstorms.
The gap shrinks on satellite
By 0115Z, that severe line of thunderstorms to the south moved into western Kansas. A line of storms developed on the northern extent of this area of severe thunderstorms bridging the gap shown very clearly in the infrared satellite image above. At this point the flight was still in southwest Iowa just about to cross the Nebraska State line. Even if this image didn’t become available for at least 15 to 20 minutes later at 0130Z, it was plenty of time to notice this explosive area of convection was quickly filling this gap.
About 20 minutes before Delta Flight 1889 penetrated this line of storms, the gap had completely closed with the color-enhanced infrared satellite image showing very cold (high) cloud tops along the route of flight.
The gap is all gone
About 20 minutes before the crew diverted to Denver at 0205 UTC, the image above shows the gap is now completely gone as these two areas of severe convection continue to mature and merge into one mesoscale convective system (MCS). Unfortunately, the crew of this Airbus A320 did not have access to critical weather data such as this. A simple three hour loop of this color-enhanced infrared satellite image could have given the pilots enough information to recognize the gap was closing and choose a better route to prevent this kind of encounter from occurring.
The view from the ground
The local ground-based NEXRAD that is updated every five minutes had even more details that might have suggested the gap would quickly disappear. Once again, this kind of strategic weather information is not available in the cockpit of these aircraft. The 2.5 hour 0.5 degree base reflectivity loop shown below is from the Goodland, Kansas WSR-88D NEXRAD Doppler radar. The loop ends right about the time the crew diverted to Denver, shortly after being pelted by hail.
This is a loop of the 0.5 degree base reflectivity out of Goodland, Kansas. This loop shows how the gap between these two convective systems begins to quickly disappear. Radar site is in the center of this image. Source: UCAR.
At the beginning of this loop, notice a crescent-shaped area of low reflectivity returns appears out of the northern edge of the southern-most area of severe storms. This is called an outflow boundary. According to meteorologist and thunderstorm researcher, Dr. Charles Doswell, III, “Cold, stable air is the ‘exhaust’ of deep, moist convection, descending in downdrafts and then spreading outward like pancake batter poured on a griddle. After spreading outward, the leading edge of this outflow – a ‘gust front’ – which often has ascent associated with it, can develop new storms.”
This is a perfect description of what transpires next. This boundary continues to push north-northeast and helps to initiate a new line of thunderstorms that rapidly blossoms into a convective barrier in extreme southwest Nebraska leaving the crew little choice but to use their onboard radar to tactically locate and penetrate the “softest” part of this line.
The crew of this Airbus didn’t have any ground-based radar loop such as this available to them in the cockpit. Even so, most of the in-cockpit radar mosaics that general aviation pilots use every day is a volume product constructed from a composite of all elevation angles of the radar. Composite reflectivity tends to mask out important details such as these outflow boundaries. Unfortunately, most in-cockpit weather providers have chosen not to broadcast the 0.5 degree base reflectivity product like the one shown above. This includes the radar mosaic that can be received through the FIS-B (ADS-B) broadcast with Stratus or through the Baron Mobile Link for XM-delivered satellite weather.
Vertically integrated liquid or VIL is another volume product that can show the truly nasty part of the storm. This loop clearly shows how quickly the gap disappeared between these two convective areas. Source: Plymouth State Weather Center.
More is better
Furthermore, there are other NEXRAD products that can be very useful in flight. This includes another volume product called vertically integrated liquid (VIL) shown above. As mentioned earlier, composite reflectivity looks at all elevation angles of the radar for a particular volume scan and shows the highest reflectivity return in the column. VIL is similar, but is a summation of the reflectivity in the column. VIL is often an indicator of the storms’s updraft strength and has a strong link to observed hail size.
At 0055 UTC, two convective SIGMETs were active each describing an area or line of severe thunderstorms. Source: NOAA.
Severe weather and aircraft don’t mix
You might say hindsight is 20/20, but this isn’t about second guessing a pilot’s decision. Instead, it’s a plea that aircrews should have more information available to them to make better informed decisions. There’s no doubt this was a risky choice; not only a risk of hail damage, but the threat of dangerous convective turbulence. The weather on both sides of the flight path consisted of severe thunderstorms. At 0055 UTC, the Aviation Weather Center (AWC) had issued two convective SIGMETs (WSTs) covering both areas of severe thunderstorms. Whether thunderstorms are severe or not is determined by the local weather forecast offices, but was echoed in the text of these convective SIGMETs. Both advisories suggested the potential for hail up to 2 inches in diameter as shown below.
The southern most convective SIGMET was issued for a line of severe thunderstorms with hail up to 2 inches in diameter with tops above FL450. Source: NOAA.
It’s time to end this madness
It’s the middle of the second decade of the 21st century and no airplane should end up flying into a thunderstorm and encounter hail and turbulence like that of Delta Flight 1889. Was this just a case of being in the wrong place at the wrong time? Not likely. Perhaps a bit of bad timing, but it was not some kind of surprise encounter that removed the paint and dented the nose cone of this A320. Not only that, but the hail nearly shattered the pilot and co-pilot’s front windscreen making it look like something you’d see in a Hollywood movie. As Stu Ostro, a senior meteorologist at The Weather Channel, commented: “hail shafts aren’t like lightning bolts from the blue shooting way out the side of a storm.”
It’s time to start requiring commercial aircraft to have unlimited access to weather information in the cockpit – more than just onboard radar. Many aircraft equipped with Wi-Fi could easily connect to any number of ground-based weather sources and display it on a mobile device such as an iPad. Even with a device like a Stratus, the FIS-B data broadcast is still lagging way behind the available technology. So it’s time to start providing pilots with more than just basic weather data that mimics the heavy textual weather of the 1980s. There’s no doubt that getting more graphical weather data in the cockpit along with some focused training will keep professional aircrews from flying blindly into a hailstorm. Fortunately for those on board Delta Flight 1889, this flight ended well.
However, right now airlines are stuck in this information-age purgatory. Is this due to cost? Probably, but there’s no encouragement by the FAA for airlines to equip pilots with this potentially live-saving guidance. This encounter should be a wakeup call to those stakeholders in aviation safety to allow, if not require, pilots to have unfettered access in the cockpit to whatever weather data is necessary to make every flight an uneventful one. What is it going to take to make this happen? Hopefully it will not be an event that has a tragic ending. But that’s usually the way it works.