Storm Forecast
Valid: Wed 28 Jun 2006 06:00 to Thu 29 Jun 2006 06:00 UTC
Issued: Tue 27 Jun 2006 23:15
Forecaster: GROENEMEIJER

SYNOPSIS

Wednesday at 06:00 UTC a southwesterly flow is located over much of Wrn and Ctrl Europe. A vort max induced by convection over Ern France on Tuesday is expected to traverse along the periphery of a broad ridge across southern Germany, Austria/Czech eastward. A shortwave trough over Wrn France is expected to move slowly eastward.

DISCUSSION

SErn Germany, Czech, Slovak, Austria, Hungary, Srn Poland, Wrn Ukraine, Nrn and Wrn Balkans

The aforementioned vort max and outflow boundaries of Tuesday's convection will likely induce sufficient upward vertical motion for the development or reintensification of convective storms during the early afternoon over SErn Germany, the Wrn Czech Rep. and/or Austria.

Given that about 20 m/s 0-6 km bulk shear is expected, storms will likely again include splitting storms / supercells. These will have a primary threat of producing large hail, possibly very large in places.

Convection will cluster into a large bowing system that works its way eastward during the afternoon and evening hours. The system should be capable of producing rather widespread damaging winds in addition to large hail. A major threat should be very high precipitation as well with local flash flooding as a result. Note that the flash flood threat is not incorporated in the threat level.

Various numerical models including GFS, INM-Hirlam, AFWA-MM5 agree on the development of a very intense system out of this. GFS at 18Z even had a vortex with 20 m/s cyclonic winds, indicative of MCC development. If such winds develop, low-level shear could become favourable for the development of tornadoes in some places.

Numerical models do not indicate that the system will bend too far SEward into Srn Hungary and the northwestern Balkans. However, this appears to be possible, certainly as the extreme low-level moisture and hence MLCAPE, that should approach 3000 J/kg once again appears not to be fully grasped by the models.... and MCS's have a tendency to propagate towards areas of high CAPE.

More isolated convection is locally possible as well across the northern and western Balkans that could bring large hail and a few strong gusts.

France, Switzerland, SWrn Germany, northern Italy

On the approach of the trough intially over western France, rising motions are expected over eastern France leading to the redevelopment of instability on the order of about 1000 J/kg MLCAPE. Moderate ~15-20 m/s deep-layer shear over NErn France and SWrn Germany and slightly higher over SErn France and Italy should prove sufficient for the development of well-organized multicells and supercells. These should have a main threat of producing large hail, although some strong and locally severe gusts are not ruled out either. Renewed development of small bowing convection with an attendant severe wind threat cannot be ruled out either.