McCann Aviation Weather Research, Inc. offers VVSTORM as a thunderstorm algorithm that incorporates the recipe. VVSTORM examines any numerical forecast model for the necessary ingredients. Not only will VVSTORM give the location where the forecast model has the ingredients coming together, but also the time the storms will develop. The benefits of better temporal thunderstorm forecasts go beyond aviation uses. Anyone interested in thunderstorms wants to know "When?" as well as "Where?'

Hit the red button below for a technical description of VVSTORM.

Thunderstorms

Of all aviation hazards pilots fear thunderstorms the most. Thunderstorms are dangerous because of the turbulence and icing potential they cause. In fact, thunderstorm-produced turbulence and icing are likely the most severe that any aircraft could encounter.

Forecasters use an "ingredients-based" recipe to locate areas of thunderstorm potential. The concepually simple recipe is given below. The forecast challenges are 1) discerning how much of each ingredient will be present in a given environment, and 2) discerning if there are enough of each ingredient to produce a thunderstorm.

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RECIPE FOR THUNDERSTORMS

Conditionally unstable lapse rate
Parcel with a Level of Free Convection
Lifting mechanism

Find zones of forced upward lifting. If parcels in those zones can be lifted to their LFC, then the parcel will be accelerated upward by buoyance. The parcel will continue accelerating until it reaches its equlibrium level (EL). Its vertical velocity will eventually become zero which defines its top. The maximum upward vertical velocity is a measure of the storm's potential strength. If parcels cannot reach their LFC or have no LFC, then no thunderstorms form.

VVSTORM output from the 6-hour 1800UTC 9 April 2001 RUC2 forecast. Each color fill is 10 m/sec with the magenta color 50 m/sec. The storm tops for the highest updrafts are printed as 100s of feet.