CONVECTIVE FORECAST
VALID 06Z SAT 10/07 - 06Z SUN 11/07 2004
ISSUED: 09/07 20:50Z
FORECASTER: DAHL

There is a moderate risk of severe thunderstorms forecast across the SW Ukraine and NW Romania.

There is a slight risk of severe thunderstorms forecast across Romania ... Moldavia and the W Ukraine.

There is a slight risk of severe thunderstorms forecast across the extreme SW Mediterranean Sea.

General thunderstorms are forecast across E Europe and NW Russia.

General thunderstorms are forecast across SW Mediterranean Sea.

SYNOPSIS

Large-scale upper low will cover central Europe at the beginning of the forecast period ... and slowly shift eastwards on Saturday. Several vort maxima are imbedded in the intense flow at its periphery. At low levels ... plume of unstable air mass is stretching from the central Mediterranean into NE Europe ahead of the main upper low. Weak cyclogenesis is progged over the N Romaina/S Ukraine region late in the day with the exact position/timing of this feature being somewhat uncertain ATTM.

DISCUSSION

...Ukraine ... Romania ... Moldavia ... Balkans....
Wind field will remain quite strong over SE Europe. Low level moisture within the theta-e plume is quite variable as revealed by Friday's 12Z launches ... but it appears that 1000+ J/kg afternoon CAPE should be common. Latest SFC OBS show SFC dewpoints in the 17 to 20°C range over Romania which may hint at richer moisture being advected from the Black Sea into the pre-frontal environment ... though the depth of this moisture is uncertain.

TSTMS should initiate during the day along and ahead of the cold front over the Ukraine and Romania ... aided by - somewhat incoherently simulated - DCVA overspreading the front.

Kinematic fields will likely weaken to the E and S of the W Ukraine ... with 20+ m/s 0-6 km shear expected over the W Ukraine. Low-level wind fields will depend on the exact location of the cyclogenesis ... which is somewhat incoherently simulated ATTM.

Current thinking is that numerous TSTMS will form ... with best chance for mesocyclones and bow echoes exisiting over the SW Ukraine and NW Romania. Main threats will be large hail and damaging winds though a few tornadoes may occur if the low-level moisture is indeed increasing in depth and if enhanced SRH is encountered. Dominant convective mode farther E and S of the MDTshould be multicellular ... with an increasing threat of late-afternoon/evening supercells over the W Black-Sea coast as SFC pressures fall in the N Romania/W Ukraine region. These storms may as well pose the threat of the entire facet of severe convective weather.

Farther S ... thermodynamic profiles should be substantially drier ... exhibiting inverted-V characteristics. Shear will likely be insufficient for a significant supercell threat ... but short bowing lines may develop ... posing threat of severe wind gusts and some hail.

...SW Mediterranean...
Strong shear and strong large-scale forcing for UVV's are progged to overspread E Spain and the SW Med late in the day. Thermodynamic fields across E Spain are quite uncertain ATTM ... but models suggest that weak CAPE will be present. EML plume will advect off the Atlas mountains ... which is expected to contribute to weak CAPE over the extreme SW Mediterranean Sea. About 35 m/s 0-6 km shear will likely support large hail and damaging winds with any storm that forms in the environment. However ... storms along the nose of the EML will likely be elevated ... resulting in somewhat less relevant deep-layer shear. Also ... these storms are unlikely to tap helical boundary layer air. If they do ... chance of a few tornadoes exists.

Allover situation is somewhat uncertain ... and will only issue a SLGT at this time. An upgrade may be necessary on Saturday.

...Central Europe...
Showers and a few TSTMS may occur beneath the central European upper thermal low ... but indications are that convective layer will be too shallow for a great TSTM threat.

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