Storm Forecast
Valid: Sat 20 May 2006 06:00 to Sun 21 May 2006 06:00 UTC
Issued: Fri 19 May 2006 20:22
Forecaster: DAHL

SYNOPSIS

Broad and intense upper westerly flow is covering Europe ... with series of vort maxima imbedded in the flow. Vigorous vort max crossing north-central Europe during the period will be main concern for potentially severe convective development. At low levels ... main stationary baroclinic zone is stretching from the SW Mediterranean NEWD into the central Ukraine ... aligned parallel to the upper flow. Large SFC low-pressure complex is covering the North Sea and the E Atlantic ... resulting in rather strong W/SWLY SFC flow over the central parts of Europe.

DISCUSSION

North-central Europe

Challanging convective scenario expected to unfold across N France ... Benelux and Germany ahead of vigorous vort max on Saturday. Models advertise weak occluded frontal system ahead of the vort max ... which is associated with 0-3 km SRH in excess of 400 J/kg and deep shear in the 25 to 30 m/s range. Strong forcing for upward vertical motion will be in place as well ... with the instability ingredient being the main concern. ATTM models agree in producing no instability along and ahead of the weak cold frontal boundary and convective threat seems to be rather low. However ... upper-level dry intrusion should be watched for possibly overspreading the region of high SRH. In this case insolation may be sufficient to destabilize the air mass and create favorable thermodynamic environment for convective development. Also ... strong linear mesoscale ascent may be imbedded in the DCVA maximum ... which could support narrow/shallow lines of convection. Any isolated cell in this kinematic environment will have fair chances of becoming mesocyclonic ... and produce large hail ... damaging wind gusts and tornadoes. However ... ATTM there appear to be no indications that storms will indeed form amidst the region of maximized SRH ... and will not introduce a threat-level for this region ATTM. However ... situation should be closely monitored.

In the wake of the weak frontal system ... convection should be able to develop. These storms will benefit from about 300 J/kg 0-3 km SRH ... 15 m/s LL shear and 20 m/s deep shear and should have fair chances of becoming supercellular or linearly organized/bow echoes. Main threat should be severe winds gusts and marginally severe hail ... though supercellular nature and low-level kinematic and thermodynamic fields suggest that a few tornadoes may also occur.

... W Romania ... N Serbia/Montenegro

Indications are that steep lapse rates will be advected across E Europe ... and upon overspreading rather moist BLs ... to result in a couple of hundred J/kg of CAPE. Deep shear will likely be somewhat marginal ... but low-level kinematic setup seems to improve towards the evening hours across the central Balkans. Dominant convective mode should be multicellular storms capable of producing some hail and strong wind gusts ... but an isolated mesocyclone cannot be excluded. Especially over western Romania in the evening hours ... a tornado or two cannot be discounted as LL shear/SRH increases.