Avoiding Thunderstorms

If you’re planning a cross country trip this time of year, thunderstorms are a major factor. To significantly reduce your chances of running into thunderstorms or convective activity there is a very simple tactic and is almost foolproof. It also has nothing to do with interpreting charts, convective outlooks or other briefing tools. Here it is; leave early in the day. By early we mean get to the airport by 5:00AM at least, so you can get loaded, get a complete in route weather brief, file a flight plan, taxi plus run up and be in the air by 7:00AM. This will insure that you are to your destination or at least to the end of your first leg by 11:00 or 12:00. This is generally before the heat of the day has a chance to stir up potentially major convective activity. This will also help to insure more of a smooth ride for your passengers. If you have a second leg, be conservative on your go no go decision. Pay very close attention to dew points higher than 17 degrees Celsius, this means heavy moisture laden air which translates into fuel for the storm. Also gather what the weather is doing 100 to 200 miles to the windward side of your route. This will give you a good idea what kind of weather has the possibility of crossing your path. Get in route weather briefings from FSS.

An air safety foundation study of 204 thunderstorm related accidents showed that — 68% occurred between noon and 8PM, 50% between 3PM and 8PM and only 8% between midnight and 9AM. Most of these accidents occurred in the cruise phase of flight and involved pilots in 2 categories. Those with 100 to 500 hours and those with more than 1000 hours. Those with more than 1000 hours accounted for 40%.

The launch early rule is not foolproof, especially with steady state thunderstorm complexes such as the type that occur in the Midwest. These can linger for days and even intensify at night. These are called Mesocale Convective Complexes and get fed by a steady stream of warm moist air from the Gulf of Mexico. Dawn Patrol tactics will also not work against a fast moving cold front.

References: WCFC ground school, Aviation Weather Manual, AOPA Pilot May 2002

These safety tips are provided by the WCFC Safety Committee. They are intended to stimulate thought and discussion about flight safety and do not necessarily represent club policy nor are they intended to replace instruction from a qualified instructor.

Avoiding Thunderstorms