Storm Forecast
Valid: Fri 16 Nov 2012 06:00 to Sat 17 Nov 2012 06:00 UTC
Issued: Thu 15 Nov 2012 19:39
Forecaster: TUSCHY

A level 1 was issued for Crete mainly for the rainfall risk and to a lesser extent for a waterspout risk along the coasts.

SYNOPSIS

Once again a cut-off west of Portugal moves east and phases with a deepening trough over the E/NE Atlantic. Another cut-off is placed over the E-Mediterranean with negligible net-motion to the east. Therefore this low-index pattern continues for most parts of S-Europe.
Further north, a wave-train of strong troughs brings cool and unsettled conditions to most of far N-Europe with quiescent conditions further south (C-Europe).

DISCUSSION

... Portugal and parts of Spain ...

Yet another cut-off approaches the area of interest during the day. Well structured warm conveyor belt (WCB) taps into rich moisture of a (sub) tropical air mass and therefore an healthy precipitation shield is forecast to affect most of the W/S-Iberian Peninsula.

Given history of similar events in the past with minor activity of electrified DMC in a similar air mass, we kept the 50-% lightning area quite narrow. Weak lapse rates are forecast and embedded convection within the WCB is possible all day long and the main risk will be heavy rain. During the night however, mid-levels cool down from the west, which may increase CAPE in the graupel zone and electrified convection somewhat. An isolated tornado event can't be excluded along the W-coast of Portugal with significantly enhanced LL shear and surface based CAPE offshore/along the coast.

... Ionian Sea, S-Aegean Sea and Crete ...

A flat upper low is placed over that area with cool mid-levels atop SSTs of 19-23 °C. SBCAPE of 500-1000 J/kg can be expected but the winds at all levels remain weak and so is the shear. Scattered to widespread thunderstorms are forecast all day long due to weak capping and divergence aloft. Multicells with heavy rain will be the main hazard. Given enhanced T-spread between the sea surface and the air mass atop, better LLCAPE may result in a few waterspout events. Thunderstorms grow upscale betimes which causes isolated excessive rainfall amounts (GFS showing somewhat enhanced parcel layer depth and LL convergence around and north of Crete). This area was highlighted by a level 1 due to the rain risk.

... English Channel ...

Influx of modified subtropical air ahead of an approaching trough with cooling mid-levels and modest forcing may spark an isolated thunderstorm during the overnight hours. Nothing severe is forecast.