Storm Forecast
Valid: Mon 25 Nov 2013 06:00 to Tue 26 Nov 2013 06:00 UTC
Issued: Sun 24 Nov 2013 19:36
Forecaster: SCHLENCZEK

A LVL1 was issued for W and SW Turkey for large hail, severe wind gusts and excessive precipitation.

A LVL1 was issued for W Greece and the Ionian Sea region for excessive precipitation and severe wind gusts.

SYNOPSIS

High pressure dominates the western parts of Europe while an upper trough persists over the central and southern parts. Ahead of this upper trough, cyclogenesis is observed over the southeastern parts of Romania. The developing low pressure system will then move northwards. Apart from the warm sector region of this low, moist and unstable air is only found over the Mediterranean. Severe convective storms are most likely in the Ionian / Aegean Sea region where a 35 m/s upper jet streak overlaps with an airmass containing some hundred J/kg MUCAPE.

DISCUSSION

...Ionian / Aegean Sea region, parts of Greece and W / SW Turkey...

As the cold airmass enters the Mediterranean from the Alpine region, strong cooling at upper levels over the still quite warm sea surface leads to some hundred J/kg of CAPE. In addition to the upper level cooling on the NW side of the upper jet streak, warm air at lower levels is advected to the north. The greatest chance of severe weather is found over the E Aegean Sea near the W / SW coast of Turkey. Upper level winds reach 30 - 35 m/s at 500 hPa and about 25 m/s of deep layer shear coincide with instability and QG forcing ahead of the trough. It is expected that most storms will turn into organized multicells or even a small MCS may form.

In this environment of enhanced 200 - 300 m^2/s^2 SRH3, moderate vertical shear and some instability, a few storms might turn into supercells which are capable of producing large hail and severe wind gusts. An isolated tornado is not ruled out either as there exist some regions with slightly enhanced SRH1 and LL shear.

Further upstream towards Greece, there is not much instability forecast in the first half of the period but as the upper trough spreads out to the south, instability will increase over the Ionian Sea and storms will likely fire up in an environment of 20 - 25 m/s of 0-6 km shear. The possibility of supercells is not as high as in SW Turkey but an isolated large hail / severe wind gust event is not discounted either.

Both regions which are covered with a LVL1 will likely get excessive precipitation as onshore advection of warm and moist air will tend to produce long-lasting and intense convective precipitation.