Storm Forecast
Valid: Tue 30 Oct 2007 06:00 to Wed 31 Oct 2007 06:00 UTC
Issued: Mon 29 Oct 2007 17:49
Forecaster: TUSCHY

SYNOPSIS

An intense upper-level jet just south of Iceland migrates southward and increases the amplitude of a longwave trough over Europe.
At lower levels, widespread pressure fall over the central Mediterranean is forecast with a strong surface depression over Corsica and Sardinia being the final result.
An outbreak of very cold but already modified polar air is expected as strong depression just west of central Norway continues to move north-northeastwards.


DISCUSSION

... Central Mediterranean ...

This outlook is alike the last outlook of Friday in many points.
We have to deal with a surface depression, situated somewhere over Sardinia and Corsica. This feature will be nearly stationary during the forecast period while weakening.
Strongest wind field is confined to North Africa, as the subtropical jet enters the Mediterranean south of Malta. Adjacent WAA of the weakening depression south of the Ionian Sea will suppress convection although GFS indicated some low-end probabilities for a few storms for SW Greece during the night hours for the past few runs. The reason for this looks like to be increasing convergence SW of Greece and a weak short-wave trough, approaching the region from the SW. We decided to wait for further model runs / sounding informations before we start to highlight any specific area....Shear would be adequate for a few severe wind gusts.

Otherwise the main concern will be an isolated tornado report in the level-1 areas, where LL shear / SRH-1 values of 200-300J/kg will overlap with low-end to moderate instability release. The main question is how good the BL moisture quality over Italy will be. In addition, mixing ratio is somewhat lower compared to last Friday and GFS indicates weaker QPF signals well inland and we therefore decided to include mainly the coastal areas in the level-1.
The same for the coastal areas of the eastern/ northern Adriatic Sea.

...Parts of NW Norway...

As strong sub-990hPa depression continues to shift NNE-wards, intense CAA starts to affect the area of interest from the NW. As a result, rapidly steepening lapse rates and better 0-3km CAPE release will be present and we won't exclude an isolated spout report along the coast.
We also issued a small level-1 area, where strong LL shear and low-end instability overlap with a risk for an isolated tornado / severe wind gust ( the latter one because of quite strong winds at 850hPa ).

We extended the highlighted area well southward but we excluded the North Sea area, as EL temperature stay quite warm. Anyway an isolated SFLOC report will still be possible as far south as the coastal areas of NW Germany / N-Netherlands.