Storm Forecast
Valid: Fri 21 May 2010 06:00 to Sat 22 May 2010 06:00 UTC
Issued: Fri 21 May 2010 05:42
Forecaster: SCHLENCZEK
A level 1 was issued for N-central Italy for large hail, tornadoes and severe wind gusts.
A level 1 was issued for parts of the E Mediterranean mainly for severe wind gusts.
SYNOPSIS
Blocking high over W Europe will persist on Friday. A weakening upper cut-off low over the Ionian Sea will shift eastward. Hot and relatively dry air is advected towards S Iberia whereas moderately cool and moist air overspreads most parts of Europe. Except for parts of Italy, the Aegean Sea and S / SW Turkey, convection is only expected to develop in an environment with very weak vertical shear.
DISCUSSION
...N Morocco, NW Algeria...
Diurnal heating may lead to some low-end instability in a hot and relatively dry airmass. In the afternoon / evening hours, some thunderstorms may develop in an environment with approx. 10 m/s deep layer shear. An isolated severe wind gust event cannot be ruled out but storm coverage is probably too low for a level 1.
...British Isles...
Diurnal heating may create a few hundred J/kg CAPE over parts of UK and Ireland which may lead to some showers and briefly organised thunderstorms. Severe weather is not expected.
...SE-central Europe, Adriatic Sea, C Mediterranean...
In the wake of an upper trough, some low-end instability is expected to be available and thunderstorms may develop during the day. Most of the storms should be briefly organised multicells which may produce isolated marginally severe hail. The hail threat should be maximised over Hungary and Slovenia where a local maximum of CAPE is forecast.
...North-central Italy from 09Z to 18Z...
A 20 m/s upper jet streak over N-central Italy should lead to locally enhanced DLS in a region with slightly augmented SRH (100 - 150 mē/sē). Even though instability is limited, a few storms may manage to organise into multicells or supercells which may pose a threat of large hail and severe wind gusts. Rich BL moisture will lead to a low cloud base and, combined with locally 10 - 13 m/s LLS, this should allow an isolated tornado.
...E Germany, Poland, Baltic States...
Some 500 - 1000 J/kg CAPE are expected to be created in a region with very weak pressure gradients. From the early afternoon until the late evening hours, numerous thunderstorms will develop in this region. Most of the storms should be briefly organised as deep layer shear is below 10 m/s but isolated large hail and local flooding may be possible as storm motion is expected to be very slow.
...Crete, E Mediterranean, SW Turkey...
Ahead of an upper vort-max, some instability should be available near the left exit of an upper jet streak. Only a small region of CAPE is forecast along the warm side of the cold front and recent satellite images show much mid-level cloudiness. CAPE should be limited to a few hundred J/kg but deep layer shear in order of 25 - 30 m/s should be enough for organised multicells or maybe even a linear MCS. The main threat will be isolated severe wind gusts and a level 1 should be marginally warranted.
