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Introduction to Global Weather

Introduction to Thunderstorms

It is estimated that there are as many as 40,000 thunderstorm occurrences each day world-wide. This translates into an astounding 14.6 million occurrences annually! The United States certainly experiences its share of thunderstorm occurrences.

Annual number of thunderstorms the U.S. From: Koehler, Thomas L., 2019: Cloud-to-Ground Lightning Flash Density and Thunderstorm Day Distributions over the Contiguous United States Derived from NLDN Measurements: 1993-2018. Under review at Monthly Weather Review. Used by permission.

The figure above shows the average number of thunderstorm days each year throughout the U.S. (The graphic defines a day of thunderstorms as two lightning flashes within a 10 nmi (18.5 km) radius.) The most frequent occurrence is in the southeastern states, with Florida having the highest number 'thunder' days (80 to 105+ days per year).

It is in this part of the country that warm, moist air from the Gulf of Mexico and Atlantic Ocean (which we will see later are necessary ingredients for thunderstorm development) is most readily available to fuel thunderstorm development.