Storm Forecast
Valid: Wed 13 Oct 2010 06:00 to Thu 14 Oct 2010 06:00 UTC
Issued: Tue 12 Oct 2010 17:50
Forecaster: PUCIK

A level 2 was issued for Western Greece mainly for excessive precipitation, large hail and to the lesser extent for tornadoes and severe wind gusts.

A level 1 was issued for Eastern Greece, Ionian Sea and Western Turkey mainly for excessive precipitation, large hail and to the lesser extent for tornadoes and severe wind gusts.

A level 1 was issued for Corsica, Sardegna, Tyrrhenian Sea, Italy, Ionian Sea mainly for excessive precipitation.

A level 1 was issued for Tunisia for excessive precipitation, large hail and to the lesser extent for severe wind gusts.

SYNOPSIS

At midlevels, a system of high geopotentials is stagnating over Eastern Atlantic, resulting in a split flow pattern. Towards east, a significant trough will reside over Scandinavia and Western Russia, filled with the arctic airmass and surrounded by a jet-stream. During the day, sharply defined short-wave trough will rotate around the northwestern flank of the trough, over Norway. The large scale trough is connected with another one, albeit much shallower, over the Mediterranean. A second branch of the jet-stream is observed on its southern and eastern flank. Both branches will reconnect over the Black Sea.

At the surface, high pressure system covers Eastern Atlantic, Southern Scandinavia and most of Central Europe. A broad system of lows is simulated over the Mediterranean and a deep low is forecast over Western Russia. Diffuse frontal zone will surround the mid and upper level trough over Scandinavia and Russia, while another frontal zone will be observed over the Central Mediterranean, slowly progressing eastwards.

With a plume of high mid-level lapse rates overlying region of warm SSTs over the Mediterranean, broad zone of abundant latent instability is forecast with widespread thunderstorm activity.

DISCUSSION

... Western coastal areas of Greece, Albania towards Turkey, Tunisia ...

Under the WAA regime on the forward flank of the surface low, high lapse rates are simulated at mid-levels of troposphere, aiding in the development of moderate degree of latent instability. MLCAPE values will probably reach the range of 1000 to 2000 J/kg, decreasing towards north. It should be noted as well, that significant CIN values (over -200 J/kg) will be likely observed over the southern and eastern parts of this belt of latent instability. As mid and upper level jet overlie this belt, strong wind shear will be observed, with values over 25 m/s in the 0-6 km layer and over 20 m/s in the 0-3 km layer. Moreover, backing low level winds will likely result in the moderate SREH values (over 200 J/kg calculated for 0-3 km layer). These conditions are very favorable for well organised, supercellular convection with wide spectrum of severe weather types.

Thunderstorms will be initiated especially by the means of coastal convergence and along the convergence zones associated with the low and its frontal system. Numerous rounds of storms can be expected over the western coasts of Greece and Albania with the highest chance of severe in the late evening hours and night. Due to the high moisture content and probability of numerous rounds of storms, excessive precipitation might be observed locally. If well organised, especially supercellular, convection manages to develop, large hail and severe wind gusts might be observed. With low LCLs and enhanced low level shear in the coastal and inland areas, tornadoes can not be ruled out either. For Greece a Level 2 is required due to the high expected storm coverage. For Turkey and Tunisia, Level 1 seems to be warranted at the moment.

... Corsica, Sardegna, Tyrrhenian Sea, Italy, Ionian Sea ...

Due to the high moisture content of the airmass, in which thunderstorms will form and also due to the fact, that several slow moving MCS might form or numerous rounds of thunderstorm might occur, Level 1 is issued for this area for the excessive precipitation. Waterspouts are not ruled out over this area either.