Storm Forecast
Valid: Wed 08 May 2013 06:00 to Thu 09 May 2013 06:00 UTC
Issued: Wed 08 May 2013 06:41
Forecaster: PUCIK

A level 1 was issued for Western Turkey mainly for large hail and severe wind gusts.

SYNOPSIS and DISCUSSION

A negatively-tilted trough that is stagnating over the Central Mediterranean, should undergo a slow cut-off process, with slight amplification to the southeast. Towards the east, a large ridge will encompass most of Eastern Europe, its axis stretching all the way towards Southern Scandinavia. Western Europe will be under the inluence of a large cyclonic vortex, increasing in intensity, its center remaining near Ireland. Closer to the surface, widespread high pressure system will cover most of Eastern Europe, with pressure falling towards south and west.

Speaking of areas prone to deep-moist convection, there will basically be two:

1/ A large belt from Greece, Turkey towards Northern Poland, encompassing many of Southeastern and Central Europe countries. Here, a moderately steep lapse rates, along with dewpoints between 10 and 15°C, locally even higher, will contribute to the marginal to moderate destabilisation during the daytime heating. Most of the area should be under a very weak vertical wind shear, with most of the cells staying in the form of "pulse"- like elements or organised in chaotic multicell clusters. Slow storm motions might induce locally high rainfalls while very isolated downburst or marginally severe hail is not ruled out with stronger cells. Most of the thunderstorms will be initiated by local factors, such as terrain induced circulations or boundaries laid down by the overnight / morning convection. Best synoptic scale support will likely be observed towards the south of the area, on the forward flank of the trough.

... Eastern Germany / Southern Denmark ...
Exception to the weak shear regime could be E Germany / S Denmark, where DLS over 15 m/s might be observed as a short-wave trough from the Atlantic cyclonic vortex approaches. Low-level convergence should aid in the storm initiation. However, ECMWF simulates only very little CAPE for the region, in contrast to GFS. 00 UTC sounding from Lindenberg and Greifswald show rather poor mid-level lapse rates supporting "thin" CAPE profiles. Will watch this area for a potential update during the day if severe potential proves higher than expected.

... Turkey ...
To the north of the surface low, enhanced SREH, along with the moderate wind shear (with the approach of 20 - 30 m/s windmax at 500 and 300 hPa to the Turkish coastline, respectively) could overlap with moderate CAPE thanks to the steep mid-level lapse rates present over the region. Well organised multicells, including some chance of brief supercells, are expected with threats of isolated large hail and/or severe wind gusts.


2/ Another area of interest will be Western Europe, namely NW Germany, BENELUX and France. Towards the south, degree of the wind shear should increase, as 20 - 25 m/s westerly flow ovespreads Southern and Western France. However, below 500 hPa, flow will likely weaken considerably, so that 0-3 and 0-1 km bulk shear will mostly stay marginal at best. Combined with meager instability and no concentrated forcing, area does not seem to need a Level 1 attm, albeit an isolated severe wind gust report from a stronger multicell will not be impossible in this setup.