Forecast Update
Valid: Mon 02 Oct 2006 12:00 to Tue 03 Oct 2006 06:00 UTC
Issued: Mon 02 Oct 2006 12:18
Forecaster: GROENEMEIJER

SYNOPSIS

Refer to convective forecast...

DISCUSSION

Portugal...

An approaching wave in the frontal zone is expected to start affecting the western Iberian peninsula this afternoon and tonight. The associated cold front is expected to move southward over NWrn Spain and Portugal during the afternoon, evening and night.
Warm, moist air and slight instablity ahead of the cold front and strong lift is expected to lead to the development of widespread convective storms. A 25 m/s SWly low-level jet ahead of the front and strong deep-layer shear should be more than sufficient for the development of rotating updrafts/mesocylcones. This, in combination with high values of storm-relative helicity suggest a threat of tornadoes will be present.
Adittionally, some large hail and strong to severe wind gusts appear possible.

Ern France Switzerland, extreme SWrn Germany...

Models guidance suggests that convective development appears possible across the level 1 area. Strong shear and storm-relative helicity suggests that storms may develop rotating updrafts and create a low threat of tornadoes, given that storms develop at all.

Ern Netherlands, northern Germany, northern Poland.

On the northern flank of a jet stream stretching from Belgium to Ern Poland, low values of CAPE have redeveloped and severeal small storms are ongoing and will liekly continue till the mid-evening. Given the strong 0-1 km shear of about 10-15 m/s, it appear possible that one or two tornadoes develop again. An ongoing supercell at 12:00 UTC over Ern Netherlands demonstrates that the favourable conditions still exist as far west as the Ern Netherlands.