Storm Forecast
Valid: Sun 18 May 2008 06:00 to Mon 19 May 2008 06:00 UTC
Issued: Sat 17 May 2008 22:24
Forecaster: SCHLENCZEK

SYNOPSIS

A weakening upper level longwave trough remains stationary over northwestern Europe. Cold upper airmass overspreads southwestern Europe and the western Mediterranean and a cut-off process with cyclogenesis over northern Italy is expected in the second half of the forecast period. To the south of the upper low, an intense 55 m/s jet streak at 300hPa will translate northeastward with its left exit region over southern Italy around 18 - 00 UTC. An upper ridge over the eastern Mediterranean will lead to stable conditions in Greece and western Turkey.

DISCUSSION

...Northern Algeria, Tunisia, Sicily...

In the wake of the cold front over northern Algeria, diurnal heating and upper level cooling may create some hundred J/kg of almost uncapped MUCAPE. Deep layer shear in order of 25 - 30 m/s over northern Algeria and strong QG forcing in the left exit region of the aforementioned jet streak and about 300 J/kg SRH3 may allow some organized multicells and a few supercells with large hail being the main threat. The area of interest will shift northeastward during the evening and organized thunderstorms will affect parts of Sicily.

...Northern / central Italy...

There is a small region of northern / central Italy where about 20 - 25 m/s deep layer shear will overlap with a few hundred J/kg of CAPE. Although subsidence due to DAVA is expected in the early afternoon, some isolated organized thunderstorms may develop. Isolated large hail is not ruled out but limited CAPE and absence of forcing should preclude a level-one threat.

...Eastern Hungary, Serbia, western Romania...

A quite impressive EML is advected into Serbia and Romania during the morning hours. Diurnal heating may create about 1 kJ/kg MLCAPE in an environment with moderate (15 - 20 m/s) deep layer shear. As the upper level vort max approaches, isolated multicells or supercells will likely develop. Storms may produce large hail and isolated severe gusts. In the late afternoon / early evening, a MCS may form over northwestern Romania and some severe gusts could occur. Later on, this system may affect western Ukraine and southern Belarus.

...Western Ukraine, Belarus...

Recent GFS forecasts show that about 1 kJ/kg MUCAPE should be available over some portions of Ukraine and Belarus. Even though deep layer shear will likely stay below 15 m/s, some organized / pulsating storms may produce isolated large hail. The moist boundary layer should be uncapped and steep LL lapse rates as well as enhanced (10 m/s) low level shear over Belarus suggest that an isolated tornado is not ruled out.
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