Storm Forecast
Valid: Mon 13 Sep 2010 06:00 to Tue 14 Sep 2010 06:00 UTC
Issued: Sun 12 Sep 2010 17:21
Forecaster: DAHL

A level 1 was issued across the N Adriatic ... the Tyrrhenian Sea ... the Ligurian Sea ... and parts of Italy mainly for marginally severe wind gusts/hail, waterspouts, and locally excessive convective rainfall.

SYNOPSIS

Main feature of interest this period is an upper trough analyzed over central Europe on Sunday afternoon, which will continue to dig southeastwards on Monday. Thereby, its southern extension will evolve into a cut-off cyclone over the central Mediterranean late in the period ... while the residual central-European trough lifts into the Baltic States. This feature will not be accompanied by appreciable surface cyclogenesis, but CAA/DAVA in its wake will lead to an eastward expansion of Atlantic high pressure into central parts of Europe. An extensive and quite vigorous Atlantic system will reach the northwestern parts of Europe on Monday.

DISCUSSION

... North Sea ...

Although the warm-sector air mass ahead of the cold front of the Atlantic cyclone should be rather stable, there seems to be a slight chance of a narrow and strongly forced line of convection along the cold front. However, neither GFS nor WRF suggest that any instability will form while usually in these scenarios at least weak hints can be found in these models. It thus seems that overall lightning probabilities will remain below 15%. However, expect convectively augmented wind gusts with any convection that may form along the cold front.

... northern Mediterranean ...

Expect scattered thunderstorms over Italy ahead of the developing upper low. Instability should be rather meager but DLS should be in the 15 - 20 m/s range ... with a slight weakening trend during the period. Expect some of the storms to become organized, capable of isolated marginally severe wind gusts/hail along with locally excessive convective rainfall. Waterspouts may form over the N Adriatic and the Tyrrhenian Sea late on Monday.

... central parts of Europe into the N Balkans ...

Farther N over central Europe ... the severe threat seems to be rather low, though there appears to be some potential for locally excessive convective rainfall. However, overall precip amounts should be rather low so that a LVL1 is not introduced for heavy rainfall at this time.

... Black Sea ...

Convection will likely persist over the Black Sea and N Turkey throughout the period. Low-level buoyancy suggests that a few waterspouts may occur over the Black Sea. The overall severe-thunderstorm probabilities are too low for a LVL1 threat, however.