1. 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

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

3. 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

4. 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

5. 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

6. 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

7. 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