Storm Forecast
Valid: Tue 02 Oct 2012 06:00 to Wed 03 Oct 2012 06:00 UTC
Issued: Mon 01 Oct 2012 22:36
Forecaster: TUSCHY

A level 1 was issued for parts of Croatia, Bosnia and Herzegovina and parts of Hungary and Serbia mainly for an isolated large hail and heavy rain risk.


SYNOPSIS

There is not much change in the atmosphere to talk about. The upper trough, which caused the deadly storm activity over parts of the W/C Mediterranean during the past few days finally loses its teeth. No real net motion to the NE is forecast while decaying over the N-Balkan States. An ill defined upper low over Turkey shifts a bit to the NE while also weakening. In fact, both features connect and result in a negative tilted trough, affecting most of SE Europe.

A major cyclonic vortex over far NW Europe won't move that much to the E, but attendant intense wind field at mid/upper levels already affects Ireland, UK and the North Sea with windy conditions forecast. Sporadic thunderstorm activity is possible with CAA atop the warm SSTs.

DISCUSSION

... Croatia, Bosnia and Herzegovina and parts of Hungary ....

In line with the weakening geopotential height gradients, shear relaxes somewhat but 10-15 m/s DLS still persist during most of the forecast period. Models like EZ and GFS both agree well with CAPE forecasts, both showing peaks up to 800 J/kg from Croatia/Bosnia and Herzegovina and Hungary. Weak lift and the entrance reagion of a broad upper jet next to a decaying surface boundary likely cause scattered to widespread thunderstorm development. An isolated large hail event is possible during the initiation stage, but rapid upscale growth into numerous storm clusters is forecast. Strong wind gusts and heavy rain accompany that activity. Storms keep going well into the night, before a cooling BL and further weakening background forcing insert a rapid decrease of that activity.

A low-end level 1 area was added mainly due to the local overlap of steep lapse rates and 15 m/s DLS.

... N-Ireland, Scotland and N-UK ...

Sporadic thunderstorm activity occurs beneath cold mid-levels and atop the warm SSTs. Highest probabilities probably exist after sunset, when a strong vort max approaches from the west with 500 hPa temperatures dropping to -28°C or less. Strong winds accompany storms.

... W-Turkey ...

Some elevated CAPE up to 1000 J/kg persist during the forecast. Weak shear precludes organized storms, but high base and deep/dry subcloud layer may result in a few strong to isolated severe downdrafts and isolated large hail events. Strongest storms however evolve just east of our forecast area, where coldest mid-levels will be present, so no level 1 area will be issued.