Thunderstorm Tactics
By Richard L. Collins
August 2006
 I have been studying general aviation accidents for almost 50 years and it is amazing that over all this period of time we have lost eight, plus or minus a few, IFR airplanes to thunderstorms each year. It’s amazing because when I started there was little or no radar information on thunderstorms available, where now our cup runneth over with radar and lightning information. In 2004 there were eight airplanes lost in storms. They were high-value singles, light twins and a turboprop twin. All likely had some manner of weather-avoidance gear.
Apparently we need to step back and examine how all the available information is used, both in planning, the strategy part, and in flying, the tactics part. Tom Benenson, who is handling strategy, remarked when I told him to don his combat boots before writing that maybe we should call it “Shock and Awe.” Maybe, because it is shocking that some pilots don’t recognize thunderstorms for the awesome things that they are. But we’ll stick with “Strategy and Tactics.”
As we were discussing this, some mention was made that it might be addressed from the perspective of the new pilot and the experienced pilot. In truth, there is not much difference because thunderstorms don’t discriminate. Scott Crossfield, with more experience than the rest of us could ever hope to have, lost a battle with a storm in north Georgia recently. And a perusal of the accidents shows a broad level of experience. Of the eight 2004 thunderstorm accidents reviewed, only three involved pilots with less than 1,000 hours. The high time pilot claimed 30,000 hours.
The simple fact is that once the airplane is in a thunderstorm, experience might not count for much. So, the trick is to stay out of the beasts. Does experience help here? Are there effective ways to do this? Read on.—RLC
If you fly enough, the day will come when you will want to depart with a thunderstorm in the vicinity. The key to avoiding trouble here is found both in staying a safe distance from the rain and the mean looking clouds, and in visualizing the outflow from the storm. That outflow can make the surface wind shift almost instantly, and if it switches to a tailwind when you are at a tender point in the flight, you can be in a world of hurt. The big outflow comes on the side which the storm is moving toward and, as the name suggests, it blows away from the storm. Thus, logic suggests that you take off toward the storm, but that also means you would have to turn away from the storm after takeoff, which could involve an increasing tailwind in the turn, which might in itself create problems. Have another cup of coffee and let the storm pass.
Once we take off to fly in an area where storms exist or are forecast, the battle is joined. One definition of tactics is maneuvers designed to gain success. There are a number of things to guide us in doing this, so let’s look at all of them.
What we see is all important because before a cumulus cloud becomes a cumulonimbus cloud it goes through quite a mean building stage. With no lightning and no rain yet falling, it can dish out a level of turbulence that might make aircraft control difficult. Remember, thunderstorms don’t just exist. They also develop and the appearance of building cumulus gives the only clue here. For years I have flown with a sight level through which you can look to see if the tops of building clouds are above or below your level. It is also useful in judging how fast the clouds are building. If they are building rapidly, they might form into a thunderstorm. If there is any question about cumulus building through your level, best point the airplane in a different direction.
Congested cumulus clouds can be bad news if they build above your level and become difficult to avoid. They may or may not build into a thunderstorm but, again, aircraft control might be difficult inside those clouds.
The time of day often has an influence on the strength of thunderstorms. Like all meteorological rules of thumb this is not 100 percent true, but the middle of the morning is often when storms are at their weakest. Late afternoon is when they most like to make whoopee. Squall lines often pay no attention to the time of day, but I have seen strong ones weaken in midmorning.
Before leaving vision as a thunderstorm avoidance tool, I have to add something that has been said many times before. If clouds look mean, they probably are mean. Guidelines are given for thunderstorm avoidance: five miles for garden-variety storms, and I’ve seen numbers from 15 to 25 miles for severe storms. That may or may not be enough. The real distance, especially from severe storms, is obvious from looking at the clouds around the storm. If they look turbulent, they will be turbulent. The best deal is to visually stay away from any clouds associated with storms, especially severe storms that tend to be quite visible and quite obvious in intensity.
The up- or downlink of Nexrad information has added a most valuable tool to what you see. This has, in fact, greatly changed the tactics of thunderstorm avoidance. We can see the big picture, and by watching storms from afar we can get some idea of how they are changing in relation to a desired track or destination airport. This is important because the picture we get on the ground, before takeoff, is likely to change a lot if much time elapses before the area is reached.
While with vision, airborne weather radar and lightning detection devices, we used to fly toward an area of weather and make deviation decisions when we got close, now those decisions can be real tactical decisions that are made well in advance using the big Nexrad picture.
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