Storm Forecast
Valid: Fri 25 Aug 2006 06:00 to Sat 26 Aug 2006 06:00 UTC
Issued: Thu 24 Aug 2006 20:25
Forecaster: TUSCHY

SYNOPSIS

Polar front jet will be displaced well towards the south over CNTRL Europe and this pattern favors numerous places of enhanced TSTM development.
The Mediterranean area will stay dry and warm / hot.

DISCUSSION

... E-Bay of Biscay and SW France...

Main concern for this region will be the quality of airmass, affecting the level-1 area, due to marginal data reports ( offshore and no SEVIRI reports due to cloud contamination )....
Sounding datas ( 24.08. 12Z ) upstream of the highlighted area inidcate a shallow, but pretty well mixed boundary layer .
An intensifying baroclinic zone and attendant strengthening upper-level jet ( about 45° W ) will cause a weakening and splitting of the wind field over the extreme eastern Atlantic and the Bay of Biscay.... Difficult to pinpoint the final position and strength of the streaks that far out, but shear should be adequate for storm organisation ( DLS ~20m/s ) over the level-1 area...
The region will still be placed in the beneficial left-exit region, although area of best upward vertical motion becomes diffuse with time....
The lift will be enhanced by a broad and weak trough, crossing the area during the afternoon hours from the NNW...
Onshore flow will gradually increase and advection of higher dewpoints looks reasonable.... A moistening boundary layer, combined with steep LL lapse rates should yield low-end instability ( 100-200 J/kg SBCAPE ).
Right now, main concern will be the possible development of shallow supercells ( maximum instability release in lower levels, an uncapped LL-environment and broad sector of 150-350m**2/s**2 SRH at 0-1km )..... LCL will be about 500m and should yield a favorable environment for an isolated tornado / funnel report.
The level-1 area was adapted to the area of most signifcant moisture return.


...CNTRL-Germany, Poland, Slovakia and Hungary...

A pool of cold mid-level air ( ~ -20 to -25°C @ 500hPa ) will cross N-CNTRL Germany during the afternoon hours from W-E....On its southern flank, shear vectors indicate slight veering in the 0 - 5km layer and a sector of 150m**2/s**2 SRH at 0-1km should be established over CNTRL Germany.... Best instability will be displaced towards the north, but still slim instability values and aforementioned shear overlap over CNTRL Germany and a short lived tornado / funnel cloud can't be excluded .

A weakening cold front will be the focus for isolated to scattered TSTM development over a broad area extending from SE Poland, Slovakia towards Hungary....10 - locally up to 20m/s DLS and augmented LL shear will be present and an isolated short - lived tornado / severe wind gust report can't be excluded.

In all those regions, storm coverage is expected to be too low for issuing higher probabilities.

...Coastal areas of the E-CNTRL Adriatic Sea...

Up to 1000 J/kg instability and augmented LL shear , combined with low LCLs will be enough for anticipating an isolated tornado / severe wind gust report...E-ward moving TSTMs will enter a drier boundary layer and abating shear, which should preclude any significant storm organisation well inland.