Storm Forecast
Valid: Sun 14 Feb 2010 06:00 to Mon 15 Feb 2010 06:00 UTC
Issued: Sun 14 Feb 2010 06:11
Forecaster: SCHLENCZEK
A level 1 was issued for parts of the Ionian Sea, including Sicily and W Greece, mainly for tornadoes and to a lesser extent for large hail and severe wind gusts.
A level 1 was issued for the N Aegean Sea, E Greece, Bosporus region and W Turkey mainly for tornadoes and severe wind gusts and to a lesser extent for large hail.
A level 1 was issued for NW Morocco and extreme SW Spain / Portugal mainly for tornadoes.
SYNOPSIS
A large and almost stationary low pressure system, filled with cold air, is present over northern and central Europe. South of this low pressure system, a 45 m/s jet streak at 300 hPa stretches from NW Spain via NE Algeria towards Albania into the E Black Sea with two embedded shortwave troughs: the stronger one should be located over NW Tunisia on Sunday morning, the second one is present over the N Black Sea. Deep moist convection should be possible over parts of the Mediterranean ahead of the shortwave which will cross the Tyrrhenian Sea and parts of the Ionian Sea / S Adriatic during Sunday afternoon. Later in the period, moderately warm and unstable air from the Azores will approach N Morocco and extreme SW Iberia.
DISCUSSION
...Sicily, Ionian Sea, Greece, Aegean Sea, W Turkey...
Some low-end instability is expected to develop ahead of the trough near Sicily where some embedded convection has developed in a large area of stratiform precipitation. As the surface low deepens while moving eastwards, instability should increase and 15 - 20 m/s deep layer shear as well as 200 - 400 mē/sē SRH3 should be in place. Even though the warm front shield will hinder insolation, convective initiation should be expected as strong QG forcing is forecast. Discrete cells will likely become supercellular in such an environment and low level shear in order of 10 m/s combined with rich BL moisture may be sufficient for an isolated tornado. Large hail and isolated severe gusts are also not ruled out. Some parts of the eastern Mediterranean will get 24 hour precipitation sums in order of 50 mm which is below our level 1 criterion for excessive convective rainfall. Nevertheless, continuous stratiform precipitatin in combination with some embedded thunderstorms may cause local flooding.
The area with best instability / shear / SRH ahead of the shortwave trough is advected towards Greece and Albania during the afternoon and will reach the Aegean Sea and W Turkey in the late evening / night hours. Shear at all levels will increase as the low deepens and the convective mode may change from discrete supercells to linear multicellular segments that may pose a threat of severe wind gusts.
...E Atlantic, SW Iberia...
Some showers and thunderstorms will develop in moderately warm and unstable air near the axis of an upper trough that approaches Iberia from the west. A small area near the coastlines will get instability and some 15 - 20 m/s deep layer shear which should allow some organised multicellular storms. Low level winds around 20 m/s at 850 hPa may augment a threat of isolated severe wind gusts and, combined with rich BL moisture and enhanced SRH, an isolated tornado. Only the coastal region of NW Morocco and the Strait of Gibraltar with southerly LL winds are included in a level 1 area as the continental airmass over Spain is extremely dry and instability will be reduced in those regions where easterly LL winds from the continent are present. Thunderstorms will move onshore, reaching the highlighted region around midnight.
...Other regions...
Showers and weakly electrified thunderstorms are forecast for parts of the Norwegian Sea and NW North Sea in the vicinity of the upper cold core. Lightning activity is probably too sparse for a medium probability thunderstorm area. Apart from the possibility of an isolated waterspout, severe weather is not expected.
