CONVECTIVE FORECAST
VALID 06Z WED 17/12 - 06Z THU 18/12 2003
ISSUED: 17/12 00:39Z
FORECASTER: GROENEMEIJER

There is a slight risk of severe thunderstorms forecast across southern Turkey and parts of the eastern Mediterranean Sea.

General thunderstorms are forecast across parts of the eastern Mediterranean Sea, Turkey, Greece and across the western Iberian peninsula and the nearby Atlantic waters.

SYNOPSIS

Wednesday at 06Z a longwave mid/upper ridge near a line from the North Sea to Sardinia, is forecast to move slowly eastward. Downstream... a mid/upper low pressure system filled with cold air over northwestern Turkey, will likely be moving eastnortheastward to the Southern Black Sea during the forecast period. A rather strong cyclonically curved jet is forecast around the western, southern and southeastern flanks of the system. An eastward moving northwest-southeast oriented trough over the western Atlantic is forecast to reach the western Iberian peninsula late Wednesday evening.

DISCUSSION

...Southern Turkey, eastern Mediterranean Sea....
An eastward moving cold front is forecast to be located from near Antalya southward at 06Z. East of this front a moist and moist-adiabatically stratified troposphere is forecast, in agreement with the 12Z soundings of Isparta (17240) and Athalassa (17607). At most a few 100s of J/kg CAPE may locally be present in this air-mass, limiting the severe potential. However, very strong deep-layer (~30 m/s 0-6 km shear) and low-level shear (~10...15 m/s 0-1 km shear) are forecast in the area as well as forcing for upward vertical motion along the front. In fact, along an near the cold front... thunderstorms have already been going on during the previous forecast period and these are expected to continue during Wednesday morning before moving out of the forecast area. The high shear values suggest that rotating updrafts / embedded (mini) supercells are possible locally, yielding a chance for high wind gusts and a minor threat of large hail. Given that the LCL height is forecast to be low, a tornado or waterspout or two can also not be ruled out.

To the west...postfrontal storms that were going on during the previous forecast period are expected to continue. However, these storms develop in a low-CAPE environment and significantly lower wind shear. Therefore these storms are not expected to be severe.

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