THUNDERSTORMS FAVORABLE CONDITIONS: UNSTABLE AIR INITIAL UPDRAFT HIGH MOISTURE CONTENT OF THE AIR LATENT HEAT RELEASED BY WATER VAPOR CONDENSATION INCREASES BUOYANCY OF RISING AIR COLUMNS AND MAKES THEM SELF-SUSTAINING

THUNDERSTORMS GREATEST DANGER IS FROM THE VERTICAL CURRENTS WHICH CAN CAUSE AIRCRAFT DISINTEGRATION THREE STAGES OF LIFE CYCLE: CUMULUS MATURE DISSIPATING

THUNDERSTORMS SEVERITY GOVERNED BY MAKE-UP OF THE MATURE STAGE UPDRAFT MAY EXTEND FROM EARTH SURFACE TO SEVERAL THOUSAND FEET ABOVE VISIBLE CLOUD TOPS IN CUMULUS STAGE, TINY CLOUD DROPLETS GROW INTO RAIN DROPS AS CLOUD BUILDS UPWARD WHEN DROPLETS REACH SIZE THAT CANNOT BE SUPPORTED BY UPDRAFT, THEY FALL

THUNDERSTORMS MATURE STAGE STARTS WITH FALLING DROPLETS IN “LIMITED STATE” T-STORM, MATURE STAGE SELF DESTRUCTS WITH UPDRAFT UNABLE TO SUPPORT RAIN DROPS, AND PRECIPITATION FALLING THROUGH UPDRAFT, AND DOWNDRAFT DEVELOPING IF UPDRAFT AND DOWNDRAFT REMAIN BALANCED, GET STEADY STATE T-STORM

THUNDERSTORMS STEADY-STATE T-STORM HAS EXTREME TURBULENCE AND POSSIBLE LARGE HAIL GOOD INDICATOR OF STEADY-STATE STORM IS SURFACE TEMP AND DEWPOINT (IF DEWPOINT 50 F OR MORE, WITH 30 F SPREAD BETWEEN TEMP AND DEWPOINT, SEVERE) “LIMITED STATE” T-STORM MAY LAST 20 MINS TO AN HOUR STEADY-STATE MAY LAST 24 HOURS AND TRAVEL 1000 MILES

THUNDERSTORMS PILOT ACTIONS: AVOID T-STORMS DO NOT FLY BELOW - DESTRUCTIVE SHEAR TURBULENCE POSSIBLE AVOID CELLS BY 20 MILES - HAIL AND VIOLENT TURBULENCE POSSIBLE REDUCE AIRSPEED TO VA IN T-STORM VICINITY MAINTAIN STRAIGHT AND LEVEL ATTITUDE ON HEADING TO MINIMIZE TIME IN STORM AREA - DON’T ATTEMPT TO HOLD ALTITUDE IN VERTICAL DRAFTS

THUNDERSTORMS THUNDERSTORM CONDITION 2: THUNDERSTORM CONDITION 1A: CONDITIONS FAVORABLE FOR T-STORMS WITHIN 40 NM OF STATION AND/OR WITHIN 6 HOURS THUNDERSTORM CONDITION 1A: T-STORMS PRESENTLY WITHIN 40 NM AND EXPECTED TO AFFECT STATION THUNDERSTORM CONDITION 1: T-STORMS IMMINENT AND WITHIN 10 NM CONDITION 1 - REFUELING AIRCRAFT PROHIBITED CONDITION 2 - REFUELING PERMITTED