With the onset of winter, as pilots, we must shift our flight planning and weather analysis from assessing convective threats to icing and cold-weather hazards such as icing, frozen precipitation and fast-moving cold fronts. Going into the colder months, we need to have a strategy for gathering and understanding all the weather data to make sound go/no-go decisions during the winter.
Where to start: First take a look at the big picture, what meteorologists call the synoptic situation. The latest surface analysis, prog charts and significant weather outlooks will give you a pretty good idea of what’s happening in terms of major weather systems affecting your route. Airmets are also good products to review as they advise of weather that may be hazardous – other than convective activity – to light aircraft, as well as larger planes. Airmets are typically issued for conditions that are widespread, meaning it covers at least 3,000 square miles, and are issued in six-hour periods.
As a quick review, airmet components consist of instrument meteorological conditions (Airmet Sierra), turbulence (Airmet Tango) and icing (Airmet Zulu). Gone are the days of trying to decipher and visualize long airmet codes. Today, with a few clicks, we can view a graphical representation of airmets.
Cold fronts, especially fast-moving ones, often trigger convective activity as colder air overtakes and plows under warmer air. In the wintertime, our concern with convective activity is its ability to lift substantial amounts of moisture to altitudes where the temperature is below freezing. The cloud droplets are cooled to temperatures below 0 degrees Celsius and yet can remain, for a time at least, in this liquid form.
Warm fronts, defined as warmer air overtaking and being gradually lifted up and over colder air at the surface, often have a more limited vertical extent than those associated with cold fronts. However, the area over which the clouds spread is often greater, which can spread low ceilings and limited visibility over a similarly larger number of potential destinations and alternate airports under consideration for our planned trip.
The most serious possibility that warm fronts present is freezing rain or freezing drizzle. Rain forming in the clouds in the overrunning warm air falls through colder air below the frontal surface. If the temperature of this air is less than 0 degrees C, the raindrops will initially be supercooled. Ultimately, given enough time and distance of fall, something will trigger the freezing process in these raindrops. The greatest potential hazard from this warm-front situation arises when the falling supercooled raindrop encounters some object, like our airplane (also cooled by passage through the subfreezing air to a temperature of less than 0 degrees C), which triggers the freezing process. The result is often a rapid, large buildup of clear ice.
Thankfully, we’ve got some excellent tools for pre-flight planning. The Current Icing Potential (CIP) is an online display of high-precision maps and is updated hourly. It identifies areas of potential aircraft icing produced by cloud droplets, freezing rain and drizzle. The Forecast Icing Potential (FIP) tool depicts icing hazards up to 12 hours in advance. It provides color-coded maps of icing potential from altitudes of 1,000 to FL290 MSL.
In ForeFlight, there is a robust suite of icing products (including CIP & FIP) that allow you to view the forecast for the severity probability of ice and the lowest freezing level. You can also find these depictions on the FAA ADDS website.
Once we have the big picture, we will want to start looking at specifics of the reported and forecast conditions at our departure, destination and alternate airports. En route surface reports may also provide insight into whether a front or pressure system is behaving as predicted. Pilot reports near our departure airport can be valuable data for our decision-making process. As long as the PIREPs are current and in a relevant position, they can provide a glimpse of conditions as they existed at the time of the report, especially cloud bases and tops and any ice encountered.
You are probably familiar with a forecasting product called Model Output Statistics (MOS) forecast alongside the traditional TAF. As the name implies, MOS is derived from weather forecasting models, including the NAM (North American Mesoscale) and GFS (Global Forecast System.) MOS takes the long- and short-range model guidance and attempts to produce an objective and more useful site-specific forecast. MOS is used by forecasters at the NWS to help generate TAFs but is never used solely for constructing the TAF.
MOS does have limitations. It cannot “fix” a bad or faulty model forecast. If you use MOS, verify against METARs, satellite and radar data to ensure the MOS guidance appears on track. Also, MOS tends to be less accurate for extended forecasts. In fact, a MOS forecast beyond 72 hours isn’t much better than using climatology averages. Finally, MOS is not good at predicting extreme conditions. All that said, MOS is best used for tracking trends.
Once you’ve gathered all the pertinent weather information, consider these questions:
- Where are the fronts moving relative to your departure, route and destination?
- Where are the cloud tops? If you can get on top, will you be able to stay on top?
- What are the cloud bases along your entire route?
- Where is the warm air?
- Are the surface winds within my personal minimums?
- When is sunrise and sunset? Short winter days may mean some flights may push into darkness, which brings its own hazards. (You’re night current, yes?)
- What are the runway surface conditions like? Pick up the phone and call the destination FBO who has eyes outside.
- Is every system on your aircraft operational, such as prop heat, pitot heat, windshield defroster, anti-ice systems, lights, etc.? Check functionality prior to launching.
- Do I have plenty of fuel? Plan conservatively, especially in winter when winds can be stronger than forecast.
- What’s your out? Regardless of your experience, recent IFR time and equipment, never leave yourself without an out. What if conditions rapidly deteriorate? What if you have an unexpected mechanical issue? Always plan out your alternate courses of action, even if it means you return to better weather conditions behind you.
For more great information on icing and cold weather ops, check out AOPA’s excellent content: www.aopa.org/Pilot-Resources/Air-Safety-Institute/Safety-Spotlights/Icing-and-Cold-Weather-Ops.
Tribute to My Friend Kevin Dingman
If you are a longtime Twin & Turbine reader, you most likely have enjoyed reading “From the Flight Deck,” one of the longest-running columns to be continually published in any monthly aviation magazine. Kevin Dingman has served up wit, sage advice and a clever turn of phrase to the T &T family for more than a decade.
In the summer of 2010, as the Twin & Turbine editor-in-chief, I received an email from a reader detailing his harrowing experience of an MD-80 engine failure during takeoff from Miami International. Intrigued, I called him, and after a short conversation, I insisted he write an article about it as there were several great lessons he imparted. I also quickly caught onto his hilariously dry sense of humor and how he used it effectively in his storytelling.
Kevin at first demurred, saying he wasn’t a professional writer, but eventually he agreed to give it a go. That article became the genesis for a regular column. Since then, I don’t believe Kevin has ever missed a deadline.
If you’ve read Kevin’s work through the years, you know how much flying is a part of his being. A former F-16 pilot and Air Force veteran, flying has defined his professional legacy but is also deeply personal to him. Planes are more than machines; they have the ability to invoke great joy, angst, frustration and nostalgia. (Remember his article on anthropomorphism?). He once wrote, “Every plane is deserving of our appreciation and respect. It’s something we have to remember when talking about our planes to others. I try to start off with several compliments about someone’s aerospace vehicle before I list the things about mine of which I’m proud.”
In 2016, he volunteered to ferry American Airlines’ last MD-80 to the Roswell, New Mexico boneyard. CNN documented the flight (which you can still find with a quick Google search) and captured Kevin’s emotional farewell to an airplane as it reached its final resting place. If you know Kevin, you know how much he loves the Mad Dog.
Fast-forward to the summer of 2021: Kevin sent me a short note announcing his last flight as captain at American Airlines. He was honored with a water cannon salute as he taxied an AA Boeing 737-800NG (featuring the airline’s “legacy” tail insignia) to the gate for the final time.
Congrats Kevin, on your retirement and all that you’ve accomplished. Keep flying that Duke and writing nuggets like this: “We’ve all tasted flight, and someday you will ‘walk the earth with your eyes turned skywards, for there you have been and there you will long to return’ (da Vinci).” Still though, for now, “We’re still flying, and that’s enough.”