Storm Forecast
Valid: Mon 13 Jan 2014 06:00 to Tue 14 Jan 2014 06:00 UTC
Issued: Mon 13 Jan 2014 02:20
Forecaster: TUSCHY
A level 1 was issued for the Gulf of Genoa mainly for heavy rain.
SYNOPSIS
The mid / upper streamline pattern features two major troughs ... one over western and one of eastern Europe. Ridging in-between does not look healthy at all and will be a transient companion for C-Europe. A weakening upper low south of Italy moves to the east and affects the Ionian and Aegean Sea during the forecast.
DISCUSSION
... Moldova, SW Ukraine and parts of the W-Black Sea ...
A forced line of shallow convection along a SE-ward ploughing cold front and beneath the left exit of a pronounced 700-500 hPa streak likely results in a swath of strong to isolated severe wind gusts next to a few marginal hail events. Lightning activity at the time of writing is not high (only spotty activity), but expect ongoing activity here and there along that front. Despite the wind gust risk, weakening gradient winds at 850 hPa keep confidence low regarding the issuance of a level 1.
... S-Ionian Sea, Crete S-Aegean Sea ...
Decoupling of a dissolving mid/upper vortex from an ill defined low-level circulation results in a broad area with isolated to scattered thunderstorms ... mainly during the overnight hours. Eastward spreading plume of colder mid-levels causes initiation around Crete with gusty winds, marginal hail and bursts of heavy rain. The SW coast of Greece experiences enhanced convergence and BL moisture along the downstream side of the diffuse LL vortex to the west. Slow moving showers and isolated thunderstorms are possible with heavy rain the main hazard. Numerous pronounced convergence zones are forecast over the area of interest. With modest LLCAPE, an isolated funnel/ tornado event is possible. The overall risk does not seem to justify a level 1 for now.
... NW/W France and UK ...
Onshore flow advects a marine and well mixed air mass far inland. Beneath cooling mid-levels, some low-end SBCAPE may be realized. SRH-1 up to 200 m^2/s^2 and low LCLs may cause an isolated funnel/short-lived tornado event over NW France during the daytime hours. Otherwise the main risk will be gusty winds and sleet.
Strong QG forcing is forecast over S-UK, where a disorganized line of showers/isolated thunderstorms should move well inland. A sharp wind shift, low LCLs and some onshore CAPE could result in a few better structured cells with an isolated short-lived tornado report (forecast soundings offer up to 260 m^2/s^2 SRH-2 and LCLs below 500 m). Marginal hail and gusty winds however will be the main hazard.
... Ligurian Sea ...
A developing depression causes 850 hPa winds to back and increase in strength during the evening and night hours, while 500 hPa temperature decrease from west to east. Not much offshore CAPE is forecast, but this kind of setup could still cause a N/S aligned line of more or less organized and slow moving showers/isolated thunderstorms with a gradual motion to the east during the overnight hours. Amounts of 50-80 mm/24h are possible, which would not justify a level-1, but combined with upslope flow along the coast, 100 mm/24h may be realized at a few spots. Hence a small level area was added.
