Thunderstorm season has begun and, admit it or not, pilots fill with a certain dread. Anyone planning a cross-country flight of any duration has to wonder if thunderstorms will become a factor. The concern really ratchets up if a flight service station weather briefer mentions a chance of convective activity. Same deal if your own Internet weather sources turn up any hints of convection.
As I'm sure you're well aware, there are many National Weather Service forecast products that give thunderstorm warnings. We'll discuss some of them in the next installment of "Wx Watch." But for now, let me give you the single most important tactic in avoiding thunderstorms. This is simple advice, and it's almost foolproof. Plus, it has nothing to do with interpreting charts, convective outlooks, or other sometimes-confusing briefing tools.
Ready to copy this advice? OK, here it is:
Take off early in the day. So early that you'll arrive at your destination before noon. That's it. This is all you need to do to significantly reduce your chances of running into thunderstorms in the warmer months of the year.
By "early in the day" I mean early. This means getting to the airport at 5 a.m. — or even earlier — checking the weather, and taking off before 7 a.m. Light general aviation airplanes typically have enough fuel capacity to permit endurances of three and a half to four hours of flying, so you'll arrive at your destination no later than 11 a.m. with comfortable fuel reserves. You say you have a second leg to fly? Then be conservative with your go/no-go decision if conditions are ripe.
It's no secret that thunderstorms are more likely to occur late in the day, when surface heating is at a maximum and thermals create the building cumulus clouds that can quickly turn into full-blown storms. This is especially true in areas with high dew points. High dew points (say, above 65 degrees Fahrenheit/18 degrees Celsius) mean humid, moisture-laden air — and plenty of storm fuel. As temperatures rise during the day — reaching a peak in the 4 to 5 p.m. time frame — this moister air gets a huge upward boost, condensing into clouds with ever-larger droplets as it rockets into unstable air aloft.
An AOPA Air Safety Foundation study of general aviation weather accidents showed that most thunderstorm-related accidents — 68 percent of 204 accidents — occurred between noon and 8 p.m. Just over 50 percent occurred between 3 p.m. and 8 p.m. Only 8 percent happened between midnight and 9 a.m. Surprise, surprise.
Other major elements in the thunderstorm accident profile round out the risk factors. Pilots taking off under instrument flight rules into reported thunderstorm activity, pilots trying to fly in or around storms, and pilots continuing VFR flight into instrument meteorological conditions were named most often in the top-ten list of pilot errors. Most thunderstorm accidents happened in the cruise phase of flight, in the months of June through August, and involved pilots in two experience categories — those with 100 to 500 hours' total time (34 percent) and more than 1,000 hours (40 percent). But for me, it's the accident time frame that speaks the clearest message.
It can be difficult to make a dawn liftoff — really difficult if you have passengers who don't understand thunderstorm behavior. Let me give you examples from my experience.
I was to fly three nonpilot, non-weather-minded passengers to the beach. This was a vacation trip, natch. In spite of my urgings to make a dawn-patrol departure, the three arose somewhere around 8 a.m., then lolled around the house for another hour or so, drinking coffee and packing. The whole time, I was trying to urge them on, telling them about how flying late in the day can mean turbulence and yes, even thunderstorms.
I was becoming a very unpopular Dutch uncle, a scold, a bring-down. In short, not very vacationlike. That's because I'd been briefed about the risk of severe storms along the route later in the day. By the time I'd herded my passengers into their cars and we'd arrived at the airport it was 11 a.m. Then came the preflight check of the airplane, the loading of the passengers (who by now I had come to consider more load than passengers), the final check of the weather (of course, a few random air-mass precipitation cells had begun to pop), and the — yes! — takeoff at noon. Long story short: An hour later we were on the ground, waiting out a line of thunderstorms.
Here's another tale from my rain-soaked logbook:
Flight of two. Me with more weather-flying experience than the other pilot. I'm up at 5 a.m.; other pilot sleeps in until 7 or so. I let him get the preflight weather briefing, but I get one of my own at 5:30. He gets his at 9. Weather's supposed to be good, he says. OK, fine.
You guessed it. We get to the airport at noon and futz around for another hour. While he preflights his airplane, I'm on the cell phone, getting the last word on the weather — a very, very important step before departure. Now it's not so fine. Embedded cell tops at 25,000 feet and rising fast.
Now he's ready to climb in and taxi out. I break the news and we end up circumnavigating some huge buildups right across our flight-planned route. It turned out well, but only because I made that last-minute check and because we were able to keep our distance visually from the (very impressive and numerous) cumulonimbus clouds. We squeaked between a couple of doozies. If we had been flying in clouds the story could have had a different outcome.
All of this could have been avoided by launching early. And I'm certain that many of those 204 thunderstorm accidents (two-thirds of them fatal) could have been avoided by the same ultra-simple tactic.
So let's resolve to do our best this season to:
- Wake early, launch early.
- Get a good preflight briefing. Compare it with yesterday's predictions. Any changes for the worse?
- Make sure your passengers' feet hit the floor by 5 a.m. Be a Dutch uncle in the name of safety. They'll find you annoying now, but thank you later for the smooth ride and nice views.
- Check the weather just prior to takeoff. Has it gone downhill since you last checked? If so, reconsider the flight.
Will the launch-early rule always work? Of course not. Steady-state thunderstorm complexes of the sort that plague the Midwest can linger for days, and even intensify at night. These mesoscale convective complexes (MCCs) are fed by a constant flow of southerly winds that shunt moisture from the Gulf of Mexico northward. MCCs often park themselves to the northeast of large high-pressure systems. They're huge, and have been known to affect entire states. Dawn-patrol tactics won't work against them, or .ny storms associated with fast-moving cold fronts. In fact, their thunder may be your wakeup call!
E-mail the author at [email protected].
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