CONVECTIVE FORECAST
VALID 06Z THU 18/09 - 06Z FRI 19/09 2003
ISSUED: 17/09 18:48Z
FORECASTER: HUGO

General thunderstorms are forecast across CENTRAL EASTERN EUROPE

General thunderstorms are forecast across SICILY & THE SURROUNDING AREA

SYNOPSIS

Large anticylonic feature will dominate over the majority of Europe throughout the forecast period in association with a well amplified 500mb long wave ridge...A sharpening long wave trough over parts of Northwest Europe will bring increasingly unsettled conditions to parts of Northern Britain and across a large section of Scandinavia...A weak surface low pressure to the Southwest of Italy will be present throughout the forecast period in association with a weak 500mb trough and vorticity...No severe thunderstorm development is expected during the forecast period...

DISCUSSION

...CENTRAL/EASTERN EUROPE...
A weakly unstable Northerly flow on the Eastern flank of the large anticyclone in association with a surface cold front feature and trough will bring the risk of some scattered thunderstorm development during the course of the day...Forecast soundings for the region show MLCAPE values to be no greater than 400 to 600j/kg and lifted index values no lower than around -2C...With little or no significant shear any thunderstorm activity will be single celled and will bring nothing more than some small (5-10mm) hail...Any convection will quickly decay during the late afternoon/evening...

...SICILY & THE SURROUNDING AREA...
The small region of surface low pressure and trough in association with a weak region of upper forcing will bring the risk of thunderstorm activity to Sicily and the surrounding region during the course of the afternoon and for a time during the evening...Forecast soundings for the region show a completely unstable atmosphere with possible cloud top heights towards 30,000ft...MLCAPE values for the region are generally between 400 to 600j/kg but some SBCAPE values are in excess of 1000 to 1,200j/kg...Lifted index values are forecast to be between -2C and -4C...With deep layer shear (0-6KM) expected to be less than 10KT and with little or no helicity to speak of any thunderstorm activity is likely to be single celled with little or no significant organisation, but with some reasonable CAPE values and a WBZ height of between 10,000 to 10,200ft there is scope for some small to medium sized hail (1-2cm)...Convection will decay towards the latter stages of the afternoon and into the evening period...

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