Storm Forecast
Valid: Mon 18 May 2009 06:00 to Tue 19 May 2009 06:00 UTC
Issued: Sun 17 May 2009 22:45
Forecaster: PUCIK
A level 1 was issued for Turkey mainly for large hail and severe wind gusts.
SYNOPSIS
A broad cyclonic vortex with center over Great Britain will persist during the forecast period and prevailing SWly flow is expected over most of W and Central Europe with attendant WAA regime. A mid-level cut off low will slowly fill over southern Greece with only slight movement to the east. At the same time a ridge will affect the weather conditions across eastern part of Central Europe. At the surface, very weak pressure field is dominating most of Europe with the only deeper low remaining almost stationary over northern part of England. A weak cold front will be making its way across Central Europe to the east, having crossed Czech republic and Western Poland by Tuesday morning.
DISCUSSION
... Northern Germany / Denmark...
GFS simulates few hundreds J/kg of MLCAPE over the region whilst ECMWF indicates instability only over Northern Denmark. A mid-level impulse will provide QG forcing and deep moist convection is expected to initiate. Storms should stay mostly weakly electrified and low topped due to the marginal instability. Strong DLS will exist especially over Northern Germany, but the degree of storm organisation remains questionable as shear in the lowest 0-3 km should remain weak, mostly below 10 m/s. Moreover, the release of instability is most uncertain exactly in the area, where the belt of strongest DLS will exist and therefore, at the moment, severe weather risk remains too low to warrant a Level 1
...Greece, Italy, Balkan states, Romania, Bulgaria, Austria, Czech republic, Poland...
Mostly diurnally driven thunderstorms are anticipated across these countries with some frontal support for the storms developing over Czech republic, Poland and Austria. GFS and ECMWF both show clear instability signals over the few consecutive runs, although GFS remains quite enthousiastic concerning CAPE values when compared to ECMWF. Nevertheless, widespread values of MLCAPE over 500 J/kg will probably be realised with locally enhanced values over 1000 J/kg possible. As only very weak wind shear is anticipated, single cells or multicell clusters will remain the primary convective mode. In the stronger cells, very isolated occurence of large hail can not be ruled out ( but at the moment, it is very difficult to pinpoint the exact location where stronger convection will take place and issue a small Level 1 for such an area - this might be the subject of a possible update) as well as marginally severe wind gusts as drier mid-level airmass is forecast by models leading to the enhanced Deltha Theta-E values over 12K.
...Turkey....
Favourable kinematic profiles are expected over Turkey, with DLS between 15 - 20 m/s and shear in the lowest 3 km over 15 m/s. Futhermore, veering of the low level winds will lead to enhanced SREH with more than 250 J/kg in the lowest 3 km so overall environment should be supportive of well organised multicells or even brief supercells. Both GFS and ECMWF show moderately unstable environment with CAPE values between 500 and 1000 J/kg. Considerable problem should be the very warm airmass advected ahead of the surface low, leading to high CIN values, so that GFS shows only very spotty initiation. ECMWF shows more widespread precipitation and therefore, level 1 is issued for the region where isolated severe hail or wind gusts are possible. The initation seems to be most likely close to the coast, where the less "hot" airmass and probably lower CIN values will be placed.
