Storm Forecast
Valid: Wed 24 Oct 2012 06:00 to Thu 25 Oct 2012 06:00 UTC
Issued: Tue 23 Oct 2012 23:33
Forecaster: PUCIK

A level 1 was issued for Western / Southwestern Iberia mainly for excessive precipitation and to the lesser degree for tornadoes.

A level 1 was issued for Sardegna, Corsica, Siciliy and Southern Turkey mainly for excessive precipitation.

SYNOPSIS

A complex synoptic scenario will evolve during the forecast period. A set of cut-off lows will dominate the conditions over the Central and Eastern Mediterranean, increasing the lapse rates and contributing to the DMC activity over the region. To the west, an active cyclonic vortex with attendant surface low and a weak frontal system are predicted to affect Iberia, especially its western part and filling in towards Thursday morning. Towards north, quiescent and stable conditions will remain over most of Central Europe while a very cold airmass with the trough begin amplifying towards the south over Scandinavia.

Most of Western, Northern and Central Europe remain in very stable or too dry conditions, so that the only region with isolated to scattered thunderstorms activity will be Southern Europe, discussed in more detailed below.

DISCUSSION

... Western, Southwestern Iberia ...

As cyclonic vortex approaches the coastline of Western Iberia, a belt of enhanced low-level moisture is advected towards northeast by 15 m/s 850 hPa winds. No significant overlap with steep lapse rates is forecast, so that instability will likely stay marginal at best. Strong DLS is forecast in the southwestern part of Iberia, over 20 m/s. The most probable form of convection will be a linearly oriented MCS with parallel stratiform region forming along the IPV belt. Low end severe weather threat will exist from the excessive precipitation - as numerous rounds of convection are possible, especially for the southwestern part of Iberia will combine with rather low LCLs and high RH in the lower to mid troposphere. An isolated tornado event is not ruled out either especially towards the evening hours, when increasing SREH and LLS might contribute to the low level rotation of the updrafts.


... Sardegna, Corsica, Sicily ...

In conjuction with the cut-off low, at its forward flank a belt of enhanced low level moisture is simulated with moderately steep mid-level lapse rates thanks to the cool mid-levels. Trapani 12 UTC sounding from Tuesday, which was found in this belt sampled the conditions with moderate CAPE (MLCAPE around 1500 J/kg), very weak wind profile and deep warm cloud layer. It looks like conditions will not change much during Wednesday, so that potential for excessive precipitation will be present with any backbuilding, on-shore moving storms. Risk should slowly move towards south with time, so that Sardegna and Corsica will be in risk mostly during the first half of the forecast period.

... Southwestern Turkey ...

Onshore moist flow with moderate CAPE values might thanks to the orographic uplift of the airmass contribute to the training of the cells over certain locations during the day. A level 1 seems to be appropriate for this setup, especially that numerous rounds of convection will be possible.