Storm Forecast
Valid: Fri 08 Oct 2010 06:00 to Sat 09 Oct 2010 06:00 UTC
Issued: Thu 07 Oct 2010 18:01
Forecaster: TUSCHY
A level 2 was issued for NW Turkey mainly for excessive rainfall.
A level 2 was issued for the far eastern Atlantic mainly for damaging wind gusts and to a lesser extent for tornadoes.
A level 1 surrounds the level 2 areas with a more limited risk.
A level 1 covers parts of W-Spain and Portugal mainly for excessive rainfall. Also, a few tornadoes and strong to severe wind gusts are forecast along the coast of Portugal.
SYNOPSIS
Impressive warm seclusion is in full swing over the far eastern Atlantic at the outset of the forecast with pressure drop gradually settling down somewhere between 950 - 955 hPa and a constant filling thereafter. This shallow warm-core structure features two damaging wind maxima, one bound to the back-bent occlusion in the western fringe of the depression's center and another one along the warm conveyor belt. Otherwise, strong ridging/LL high pressure area affect most parts of Europe with stable conditions forecast.
DISCUSSION
... Portugal and Spain ...
A gradually eastward moving warm conveyor belt with favorable access to a (sub) tropical moisture pool to its south causes a band with strong precipitation. Thunderstorms are most probable along the coast of Portugal and SW-Spain with stratiform rain more inland. LL shear is strong with up to 15 m/s and LCLs quite low (locally below 500 m), so a few tornado reports are well possible despite the rapid clustering trend of thunderstorms. Strong to isolated severe wind gusts remain confined to the coastal areas, where boundary layer air mass will be somewhat better mixed than inland. There, WAA/isentropic lift disconnects surface winds from intense winds above. The main risk however will be strong to locally excessive rainfall mainly over Portugal and the SW coast of Spain, which caused the issuance of a broad level 1.
... W-Bay of Biscay northwards ...
A sharp trough axis and attendant surface wave race northward along the eastern fringe of the main vortex. Coupled to some mid-level dry air overspreading the western fringe of the moist warm conveyor belt and abundant lift cause a sector with modest CAPE/intense shear overlap. A rare E-Atlantic level 2 was introduced to highlight the chance for tornadoes and severe wind gusts with that activity, which probably peaks around noon with decreasing action thereafter.
... NW-Turkey ...
A low pressure area over the E-Black Sea assists in the development of a broad LLJ over the W-Black Sea. This LLJ advects a moist air mass to the NW coast of Turkey beneath cold mid-levels. Scattered showers/a few thunderstorms are forecast with heavy rainfall being the main risk. Due to the prolonged period of onshore flow and the convective nature of this event, a level 2 was introduced along the coast, where amounts up to 100 l/12h are most likely.
