Storm Forecast
Valid: Mon 14 Nov 2011 06:00 to Tue 15 Nov 2011 06:00 UTC
Issued: Sun 13 Nov 2011 16:53
Forecaster: TUSCHY

A level 1 was issued for parts of Portugal and Spain mainly for isolated large hail and strong wind gusts.

A level 1 was issued for parts of the E-Mediterranean mainly for heavy rainfall.

SYNOPSIS

Blocking omega pattern continues. Far SW and SE Europe may see augmented chances for DMC, otherwise stable conditions preclude any thunderstorm chances.
Sporadic storms may occur over the far S-Arctic Ocean and offshore over far W-Russia, as arctic air mass spreads ashore.

DISCUSSION

... S-Turkey ...

An upper low enters the E-Mediterranean and starts to influence all of that area of interest. A slowly consolidating surface low east of Cyprus assists in scattered to widespread showers/thunderstorms...mainly east of our forecast area.
Same with a strong convergence, which develops north of this low and either along the S-coast of Turkey or just offshore (model discrepancies still present). In any case, heavy to excessive rainfall affects the S-coast of Turkey . We issued a marginal level 1 for the western part of this rainfall event.

This situation will be closley monitored in case this depression remains offshore longer than currently anticipated. SSTs are in the order of 21 - 25°C, so with expected cold air mass at 500 hPa and slow motion of this depression, some shallow warm-core development can't be ruled out. Any organization may have influence on how organized the convective bands will be, which also affects the excessive rainfall probabilities.

... Portugal and Spain ...

Negative tilted upper low affects mainly the W-part of the Iberian Peninsula. With -20 to -25 °C at 500 hPa atop a maritime Atlantic air mass, roughly 500 J/kg MLCAPE seems possible mainly over Portugal and SW-Spain. Further inland, CAPE vanishes as moisture in LL mixes out. Nevertheless, some MUCAPE spreads well inland and hence a broad 15% thunderstorm area was issued.

DLS in the order of 20 m/s is present, which is adequate for a few better organized multicells...especially within the level 1. Large hail and strong wind gusts will be the main hazard. Strong LL shear remains displaced from best instability, so right now tornado probabilities remain low. At the latest after sunset, onshore thunderstorm probabilities wane but increase somewhat offshore (east of Spain).

... Far S-Arctic Ocean and onshore areas ...

A sporadic thunderstorm event is possible with meager BL moisture and very steep mid-level lapse rates. Marginal hail and strong to severe wind gusts may accompany that activity. The coverage is too isolated for any lightning area.