CONVECTIVE FORECAST
VALID 06Z SUN 13/06 - 06Z MON 14/06 2004
ISSUED: 12/06 18:05Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across central and eastern Spain.

General thunderstorms are forecast across south and east Europe.

SYNOPSIS

Positively tilted central-European upper trough will close off into a cut-off low over the N Mediterranean during Sunday. Strong zonal jet streak over the N Atlantic ... is progged to spread eastwards ... reaching Scandinavia late in the period ... with strong upper ridging spreading into W and central Europe. At low levels ... main baroclinic zone will stretch from the NRN Iberian Peninsula across the N Mediterranean and N Romania into W Russia by Sunday 06Z. As weak cyclogenesis occurs along this boundary early in the period over N Italy ... NW Mediterranean segment of the cold front will accelerate southwards ... reaching N Algier early Monday morning.

DISCUSSION

...Iberia...
Another round of TSTMS is expected in the weakly capped/weakly unstable air mass over the Iberian Peninsula. First TSTMS will likely initiate along the cold front over N Iberia ... with further TSTM development farther south as insolation reduces CINH. Vort max at the W periphery of the Mediterranean upper low is expected to overspread the Iberian Peninsula during the day ... supporting widespread TSTM development.

15 m/s 500 hPa flow will likely be present over the northeastern portions of the peninsula ... decreasing to the southwest. In addition to quite deep/dry CBLs ... this will likely favor strong evaporative cooling of the downdrafts ... and the formation of cold pools ... preferably along the eastern portions of the cold front where shear and TSTM coverage should be maximized. Main threat will be damaging wind gusts ... and possibly some hail especially if mesocyclones can form.

Some uncertainty exists with respect to the influence of the Pyrenees on the environment over NE Spain ... and orographcially-forced subsidence may render thermodynamic environment unfavorable for deep convection.

Nonetheless ... kinematic and thermodynamic setup appears to be quite favorable for an organized downburst threat ... warranting and a SLGT.

...Central Italy ... central Balkans ... Romania ... Moldavia ... S Ukraine...
Over the NW Mediterranean Sea and over central Italy ... TSTMS will likely form amidst DCVA regime along the cold front ... especially over Italy where diabatic SFC heating should support CAPEs in the 500 to 1000 J/kg range. About 15 m/s deep-layer shear is expected ... and an isolated marginally severe hail/wind event may occur. However ... allover setup appears to be too marginal for a significant severe weather threat.

Over the Balkans ... Romania and the S Ukraine storms should initiate towards early afternoon in weakly capped air mass. CAPE values will likely not exceed about 1000 J/kg. Deep shear of 15 m/s is progged over the N Balkans ... Romania and the S Ukraine ... decreasing to the south. Rather high SFC temperature-dewpoint spreads suggest that a few strong downdrafts may occur ... producing isolated severe straight-line winds. Also ... a few marginally severe hail events may occur ... especially over the central Balkans ... Romania and the S Ukraine where shear will be strongest.

...E Chech Republic ... S Poland ... NW Mediterranean Sea...
Scattered TSTMS will likely form underneath the thermal lows associated with the developing cut-off low over the N Mediterranean ... and with the remnant NRN-stream trough over E-central Europe. Severe-threat will be quite low given weak thermodynamics and weak shear ... though it looks that a few waterspouts may occur over the NW Mediterranean Sea.

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