Storm Forecast
Valid: Wed 18 Jul 2012 06:00 to Thu 19 Jul 2012 06:00 UTC
Issued: Wed 18 Jul 2012 08:07
Forecaster: PUCIK

A level 1 was issued for Central England mainly for marginally large hail and tornadoes

A level 1 was issued for Northeastern Germany and Western Poland mainly for marginally large hail and tornadoes

SYNOPSIS

Prevailing fresh zonal flow at mid to upper levels of troposphere affects most of Europe with only mild disturbances expected during the forecast period. The primary short-wave should affect Great Britain, amplifying towards the southeast with time. Another trough will reside over Eastern Europe with only little movement during the day. Between these two features, an insignificant ridge will travel over Central Europe. Closer to the surface, deepening surface low and its frontal systems will affect Western and Central Europe with warm front currently tracking over Northeastern Germany towards Poland. Behind it a WAA regime sets in. Towards the east an already occludded low pressure system will affect Northern Russia.

DISCUSSION

... Central England ...

00 UTC Camborne and Herstmonceux soundings suggest moderate to strong, mostly unidirectional DLS with steep lapse rates at mid-levels and stable low levels of troposphere. Further destabilisation might be expected during the day with approaching short-wave trough and decreasing mid-level temperatures / height falls. Albeit degree of the instability will likely be a limiting factor with only few hundreds J/kg of MLCAPE expected, strong DLS might promote some well organised DMC, including possiblity of supercells. With enhanced LLS and rather low LCLs an isolated tornado is not ruled out besides some marginally large hail with better organised and more persistent storms.

... Eastern Germany, Western Poland ...

Behind the advancing warm front, a WAA regime should provide some lift for at least marginal destabilisation as well as advection of steeper lapse rates from SW. Surface SW-ly flow overtopped by fresh NW-ly flow at mid to upper levels should provide some modest veering of winds with height and DLS values should stay around 20 m/s. LLS will likely increase towards the evening with the deepening of the surface low. Isolated to scattered DMC is simulated by most of NWP and thanks to the strong shear, well organised storms are possible. Main threat should be marginally large hail, but low LCLs, especially close to the warm front, with some enhanced LLS in the afternoon/evening hours and modest veering of winds with height point to some isolated tornado threat in case that supercells manage to form.