Storm Forecast
Valid: Mon 28 Oct 2013 06:00 to Tue 29 Oct 2013 06:00 UTC
Issued: Sun 27 Oct 2013 23:15
Forecaster: GROENEMEIJER

Note: ESTOFEX forecasts address only convective storms, not windstorms unrelated to deep, moist convection. The level areas do therefore not represent regions affected by non-convective severe wind

A level 2 was issued for SE England, N France, Benelux, NW Germany and S Denmark mainly for severe wind gusts and isolated tornadoes.

A level 1 was issued for an area surrounding the level 2 mainly for severe wind gusts and isolated tornadoes.

SYNOPSIS

An amplifying trough approaches Europe from the Atlantic ocean with a very strong SWly jet situated ahead of it. A frontal wave within the associated baroclinic zone is expected to translate very rapidly NEward during the day. The associated surface cyclone should be located over the southern North Sea by 06 UTC, near Stockholm by 18 UTC and over Karelia 06 UTC on Tuesday. The wind field on the cyclone's SE flank is expected to be very strong with severe (25 m/s) and isolated extreme (32 m/s) wind gusts occurring even in the absence of convective storms.

DISCUSSION

... SE England, N France, Benelux, N Germany, Denmark...

NWP guidance suggests that the cold front in the wake of the surface cyclone will be accompanied by narrow segments of convection with tops in the mid-troposphere. On Monday at 06 UTC, this line should be located over SE England and the English Channel extending into Brittany. It is expected to move ENE ward across the level 2 area reaching NW Germany in the mid-afternoon, and then gradually weaken. However, is not ruled out that some convective activity will also affect southern Sweden.

The strong surface wind field in which the convection will be embedded will be further by the storms to produce widespread severe and isolated extremely (>32 m/s) severe wind gusts. Given the extreme wind shear expected ahead of the convective lines (20-25 m/s 0-1 km shear) and high 0-1 SRH (400 - 500 m2/s2) some tornadoes may also develop. The threat of large hail, however, will be relatively small since the updraughts will be not that deep and probably strongest a low levels. Modest mixing ratios and high storm speeds will mitigate the threat of extreme rainfall.

... British Isles NW of the front ...

Additional convective storms are expected to the NW of the front. These will be rather poorly organized and should not pose a significant threat of severe weather. Nevertheless, small hail and mostly- non-severe winds will probably occur with some of these.