June 12, 2013
By Dan Namowitz
Thunderstorms didn’t get their fearsome reputation just from the extreme conditions a pilot can encounter by stumbling into, or too close to one. The reputation also hints at the speed at which thunderstorms can grow from puffy cumulus clouds into giant, opaque cumulonimbus.
That speed of growth is important because it helps you set a freshness date on your weather briefing and periodic updates. Since it doesn’t take long for convective conditions to develop, any conditions conducive to convection in your flight’s weather profile deserve constant monitoring.
Even if thunderstorms are not specifically mentioned in your briefing, indicators—high dew points, an unstable atmosphere, an approaching front—should put you on alert. If you will depart in a hazy, stable air mass with reduced visibility and fly toward an advancing front, be wary of embedded weather hazards.
Just before heading out, give weather radar a final glance on a computer terminal; animating the display will show you the speed, direction, and intensity of areas of precip. Not available? Then make sure you can read and decode a radar weather report. There is an example on page 12-10 of the Pilots Handbook of Aeronautical Knowledge.
Once airborne, remember that a squall line can develop ahead of an advancing front—also with little warning. Note the navaids that transmit hazardous in-flight weather advisory service broadcasts; a HIWAS broadcast may be your first clue that conditions are changing for the worse.
One of the many benefits of receiving flight following services from ATC is hearing any announcement that a convective sigmet has been issued. Follow up with HIWAS, or give flight watch a call.
Perilous is any decision to land in haste at an airport in the path of an approaching storm. If you win the race to the airport, a gust front—or worse, a microburst—could still beat you to the punch.
“The wind's downward movement is part of the danger when an aircraft flies into a microburst. But, the biggest danger is a sudden shift in wind direction,” wrote meteorologist Jack Williams in this installment of “The Weather Never Sleeps” in Flight Training magazine.
In any scenario involving thunderstorms, safety requires putting as much distance as possible between you and the rough stuff. Some pilots try to shave that margin. That’s a losing bet.
Dan Namowitz is an aviation writer and flight instructor.
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