Thunderstorm Climatology part I

Summer is ending soon, here in Romania. For thunderstorms it was a rather good year with numerous thunderstorms, although most thunderstorms were of the airmass thunderstorm type. Well organized storms didn't occur often.

On average nearly 40 thunderstorms days do occur here in central Transylvania. To see how this is distributed over the year I did some statistical research. And this is the result:






Table 1. Number of thunderstorm days for LRTM (Tirgu Mures) for the last 20 years. Data extracted from www.tutiempo.net

Season starts rapidly in the month of May, with July as peak month. However, my experience is that most severe thunderstorms do occur in the month of June, when the jet-stream is stronger. In July and August the jetstream shifts to the north (on average of course). Rapid decline of the number of thunderstorm-days is from August to September when, again on average, dry arid conditions are the norm. Besides, the air in the upper levels is warmer by then, reducing the instability.

Because the continental airmass in winter is often cold and stable, winter thunderstorms are extremely rare in Transylvania. However they do happen in the period december till february: once in four or five years or so. Mainly in cases with an active coldfront or in a situation with wintry showers in northwesterly flow.

At last I will show my own observations of thunderdays from the village of Curteni (near Tirgu Mures) with data from the last three years:

* This number may change






Table 2. Number of thunderstorm days for Curteni in the period oktober 2007 - august 2010.