A thunderstorm is one or several cumulonimbus clouds accompanied by lightning and thunder. Three Ingredients: – Lifting force – Unstable Air – Moist air

Wind shear – An abrupt change in wind direction and/or velocity Lightning Hail Tornados

Don’t land or takeoff in the face of an approaching thunderstorm. Don’t attempt to fly under a thunderstorm. Don’t fly without airborne radar into a cloud mass containing scattered embedded thunderstorms. Avoid any thunderstorm by at least 20 miles. Clear the top of a known or suspected severe thunderstorm by at least 1,000 ft altitude for each 10 knots of wind speed at the cloud top. Circumnavigate the entire area if the area has 6/10 thunderstorm coverage. Regard any thunderstorm with top 35,000 feet or higher as extremely hazardous.

If you cannot avoid penetrating a thunderstorm do the following before entering the thunderstorm: Tighten your safety belt and put your shoulder harness on. Plan a hold your course to take you through the storm in a minimum time. To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level of minus 15 degrees Celsius. Verify/turn on pitot heat, carb heat or jet engine anti-ice. Establish power settings for turbulence penetration airspeed (VA). Turn up the cockpit lights to highest intensity. Disconnect the autopilot. If using airborne radar, tilt the antenna up and down occasionally to detect other thunderstorms.

Follow these guidelines during thunderstorm penetration: Keep your eyes on your instruments, this will decrease the danger of temporary blindness from lightening. Don’t change power settings; maintain settings for the recommended turbulence penetration airspeed. Don’t attempt to maintain constant altitude; let the aircraft “ride the waves.” Don’t turn back once your are in the thunderstorm, a straight course through the storm will most likely get you out of the hazards most quickly.

Isolated / Air mass thunderstorms – Last 20min to 1.5 hours Cools the surface below the storm in the mature stage which inhibits updrafts and cuts off the storms supply of water vapor. Frontal / Steady State thunderstorms – Associated with fronts, converging winds and troughs aloft. – Sometimes embedded in cloud masses and called embedded thunderstorms Dangerous for all pilots, especially those without radar. Squall line thunderstorms – Most dangerous of all – Narrow bands of very active thunderstorms that may produce a line that is too long to detour and wide/severe to penetrate. – Produces the most intense weather hazards to aircraft Tornadoes Large hail Heavy rain Strong winds

Occurs ahead of a thunderstorm Caused by a downdraft that hits the ground and fans out in front of the thunderstorm Causes a great deal of windshear and turbulence Particularly hazardous during takeoff and landing – Near the ground – Incapable of dealing with drastic changes in wind direction and velocity Rule – Don’t land/takeoff in the face of an approaching thunderstorm

The areas forecast to have thunderstorms or severe thunderstorms are depicted to the right of the line.

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