Storm Forecast
Valid: Sun 11 Oct 2015 06:00 to Mon 12 Oct 2015 06:00 UTC
Issued: Sun 11 Oct 2015 00:28
Forecaster: TASZAREK

A level 2 was issued for S and E Greece, Aegean Sea, W Turkey and S Bulgaria mainly for the large hail, tornadoes, severe wind gusts and excessive precipitation.

A level 1 was issued for Albania, Greece, FYROM, S and E Bulgaria, W Turkey mainly for the large hail, severe wind gusts and excessive precipitation.

SYNOPSIS

Extensive Scandinavian high covers N Europe and drives cold and stable air masses into most of the N, NE and Central Europe. Over the NW Europe a weak trough with a cold front and a shallow convection approaches N British Isles. In SW Europe a trough over Atlantic Ocean will move within a forecast period into a Portugal and provide conditions for DMC especially during the nigh time hours. Another trough together with a mid geopotential shortwave moves eastwardly through Balkan Peninsula, Aegean Sea and Black Sea. Within this feature a dangerous overlap of unstable warm and moist air mas with a high low and mid-level wind shear takes place.

DISCUSSION

...S Balkan Peninsula, Aegean Sea, Black Sea, W Turkey...

During a forecast period, a low-level inflow of very moist (avg. mixing ratios ~ 14-15 g/kg) and warm (850 hPa temperature - 16-17C) air will take place over the Aegean Sea. Such air within a steepening lapse rates in front of the approaching trough result in a CAPE over the Aegean Sea up to 2000 J/kg. Increased mid-level flow with a jet streak extending from Greece to Black Sea results in a DLS up to 20-25 m/s. Impressive flow over 700 hPa pressure level exceeding 20 m/s provides also strong shear values that may be likely of organizing convection into linear feature (squall line). Given also significant directional wind shear (0-1km SRH up to 400-600 m2/s2, 0-3km SRH up to 600-800 m2/s2) and LLJ (0-1 km shear up to 15-17 m/s) an isolated and embedded supercells capable of producing damaging wind gusts, large hail and strong tornadoes cannot be ruled out. The highest risk for tornadoes falls especially in the afternoon hours on the NW Turkey and NE Greece where the overlap of favorable conditions is the best. Numerous composite parameters derived from the NWP models indicate good conditions for tornadoes over these areas as well. Persistent QG-forcing driven from the passage of the shortwave over the region with DMC in level 2 area is expected to provide favorable conditions for the formation of the MCS that is forecast to occur over the Aegean Sea in the late afternoon hours and move eastwardly into W Turkey. Although the thunderstorm motion is predicted to be quite high, impressive PW values exceeding 40-45mm create threat for the excessive precipitation and flash flooding. Most of the level 1 area is covered by the threat for the supercell thunderstorms and thus large hail and severe wind gust within these storms are possible.