Storm Forecast
Valid: Wed 11 Nov 2009 06:00 to Thu 12 Nov 2009 06:00 UTC
Issued: Tue 10 Nov 2009 23:47
Forecaster: PUCIK

A level 1 was issued for Turkey mainly for excessive precipitation and to the lesser extent for tornadoes.

SYNOPSIS

Rather complex synoptic scenario is expected over Europe during the forecast period. A large cyclonic vortex at mid and upper levels, centered over Slovakia is filled with cool airmass.
At its southern fringes, strong mid-level jet is diverted around it with windspeeds locally over 35 m/s. Another feature will be a cold-core low over Finland and extreme Northwestern Russia, surrounded by strong mid-level flow and intense forcing at its forward flank. A subtle ridge will move over Western Europe, slowly decaying as an impulse in form of a short wave trough will quickly arrive in a jet-stream and influence the weather over the British Isles and France during the Wednesday night.

At the surface a weakening low pressure system placed over Central and Southeastern Europe will slowly drift to the northeast. From the west, large and deep low will affect Western Europe in the second half of the forecast period. High pressure system is placed over far extents of Siberia with a ridge developing over Scandinavia. In cool maritime airmass over the Ionian Sea, showers and thunderstorms are expected without significant threat of severe weather

DISCUSSION

...Turkey...

Ahead of the advancing cold front, on the forward flank of the cyclonic vortex, an airmass characterized by enhanced Theta-E values will advect from the south. With cooler airmass at midlevels and strong upward motion, marginal destabilization is expected with MLCAPE values ranging from 500 to 1000 J/kg, ECMWF being even less optimistic than GFS with CAPE values only around 500 J/kg. Favorable kinematic setup under a strong mid-level jet will increase the potential for storm organisation - more than 30 m/s of DLS is anticipated and over 15 m/s of shear in the lowest 3 km. Therefore, rotating updrafts are possible even though, isolated supercellular development is quite improbable, due to the fact, that storms will probably cluster around the cold front in the strong southerly flow being parallel to this boundary.

Very strong synoptic-scale upward motion is being simulated by the models, so that storms will easily initiate and will travel quickly northward/northeastwards. Especially around the coastal areas with enhanced convergence, repetitive storm formation is possible with thunderstorm training and this combined with moist tropospheric profiles might lead to the excessive precipitation potential. Detrimental fact is that the frontal system will proceed rather quickly eastwards and potential for excessive precipitation will dimnish gradually after 06 UTC but further showers and weak thunderstorms are possible also in the post-frontal airmass.

With the favorable wind profiles, briefly rotating storms might occur and with enhanced LLS onshore (due to the friction, its values might go over 10 m/s) and low LCLs, tornado is not ruled out. Combined with excessive precipitation threat, Level 1 is warranted for this region.