Storm Forecast
Valid: Fri 18 Feb 2011 06:00 to Sat 19 Feb 2011 06:00 UTC
Issued: Thu 17 Feb 2011 23:13
Forecaster: TUSCHY

A level 1 was issued for the coast of W/NE-Greece and W-Turkey mainly for severe wind gusts, large hail and a few tornadoes.

SYNOPSIS

A strong LL depression evolves over the S-central Mediterranean during the period, moving gradually to the east. High pressure persists over N/NE Europe.

DISCUSSION

... Ionian Sea, Greece, Aegean Sea and parts of Turkey...

Neutral tilt of the upper trough shifts into a negative one, as the center of the upper low reforms within its eastern quadrant just within the left exit of the sharp cyclonically curved upper jet. Favorable forcing and upper divergence assist in rapid development of an attendant surface depression just to the east of Sicily. A warm and moist air mass spreads to the north ahead of this feature, covering the Ionian Sea during the daytime hours and the Aegean Sea thereafter. Responding to the rapidly developing surface depression, the LL wind field strengthens with high LL shear/SRH1 magnitude especially along the westward facing coasts of Greece and Turkey. Favorable overlap of shear and CAPE increase the risk for well organized storms with severe wind gusts, large hail and a few tornado reports. Level 1 areas will cover this risk. A somewhat limiting reason for a more widespread severe risk will be the ongoing separation of 20-40 m/s DLS and highest SBCAPE (despite some marginal overlap). Hence, more rapid storm clustering withing the level areas is expected.

...Sicily and extreme S-Italy ...

Despite agreement of models like ECMWF and GFS in evolving a strong depression just east of Sicily, the final placement remains still somewhat unclear, which will have major effects on a more concentrated heavy rainfall risk. Another uncertainty will be, how fast thunderstorm development over th S-Ionian Sea will be, which could limit/cut off favorable moist inflow from the SE. Local models indicate some areas with augmented probabilities for excessive rainfall (especially over S-Italy and N-Sicily). Due to ongoing uncertainties and the fact that only GFS produced QPF amounts shy below our level 1 criterion, we decided to stick with a general thunderstorm area, mentioning the potential for excessive rainfall within those areas.