Storm Forecast
Valid: Sun 20 May 2007 06:00 to Mon 21 May 2007 06:00 UTC
Issued: Sat 19 May 2007 18:07
Forecaster: DAHL

SYNOPSIS

Allover upper flow pattern will remain largely unchanged except that the W European upper long-wave trough continues to amplify and that it will merge with the cut-off low which will be located SW of the Iberian Peninsula by the beginning of the forecast period ... while SE European upper low will remain anchored over the Aegean Sea. Central and SRN portions of Europe will experience essentially quiescent SFC conditions, though weak low-pressure areas should exist over the Aegean/Turkey/Black-Sea region as well as over Spain/France.

DISCUSSION

... central France ... Benelux ... NW Germany ...

Mainly diurnally-driven TSTMS should form again over the Iberian Peninsula as well as over France and possibly also over Benelux and Germany. Deep shear with up to 15 m/s over NW Germany and central France may become marginally supportive of a few organized TSTM cells, which should predominantly be of multicellular nature. GFS simulates regions of 10 m/s 0-1 km shear over Benelux and SW Germany, but somewhat displaced from the regions of positive CAPE. Nonetheless, shear profiles and storm evolution should be monitored for possible tornadic mesocyclones over these regions on Sunday. At this time, the risk seems to be too low for a categorical outlook, though an upgrade may become necessary on Sunday.

... Iberian Peninsula ...

Better chances for severe evolution exist over the Iberian Peninsula. Deep/dry CBLs should promote strong outflow winds, which will be supported by storm-scale organization in 15 to 20 m/s DLS environment. Expect mutlicellular storms with bowing segments, and possibly also a few mesocyclones. Main threat will be severe outflow winds, though large hail may also occur, especially with the supercells/mesocyclones.

... extreme NW Turkey ... E Bulgaria ...

Some severe threat also exists over regions adjacent to the SW Black Sea where deep shear of about 20 m/s will be present per GFS solution. Region of 12 m/s LLS is expected to be present over the W Black Sea, N Bulgaria and Romania, but it seems that it will remain outside of the region of positive CAPE. Nonetheless, low LCL heights and minimal capping may be supportive of a tornado or two with the mesocyclones that may develop. However, marginally severe wind/hail should be the main threats.