Storm Forecast
Valid: Fri 15 Nov 2013 06:00 to Sat 16 Nov 2013 06:00 UTC
Issued: Thu 14 Nov 2013 14:33
Forecaster: TUSCHY

A level 1 was issued for the Balearic Islands mainly for excessive rain and a few waterspout events.

A level 1 was issued for Sicily, Malta, S-Italy and parts of the Ionian Sea mainly for excessive rain and isolated large hail (Malta). An isolated waterspout event can occur also outside the 1.

SYNOPSIS

A vigorous upper low finally drips off the westerlies and retrogrades to the southwest towards Portugal and Spain. The mid/upper level circulation gradually spins down to the surface, where weak cyclogenesis over N-Spain is forecast.
From N-France to the Black Sea, ridging remains in place with calm conditions expected. Further north, a potent 90/55 m/s 300/500 hPa jet pushes east towards N-Europe, as a low pressure next to Svalberg deepens to 940 hPa and ridging over C-Europe remains stout.

DISCUSSION

... Balearic Islands ...

Placed along the eastern fringe of the SW-ward moving upper low, modest BL moisture advection towards the Balearic Islands takes place. The combination of cold mid-levels and SSTs in the upper tens will offer enough SBCAPE of 200 to up to 800 J/kg for deep updrafts. Scattered showers and thunderstorms are forecast mainly west and south of the Islands, spreading also north during the night. Slow storm motion results in heavy to excessive precipitation and plenty of LL CAPE points to an enhanced waterspout risk.
Beyond midnight, the environment becomes favorable for a cluster of thunderstorms to approach the Balearic Islands from the SE as WAA sets in. Heavy rain will be the main risk.
Also during the night hours, conditions improve for a slow moving cluster to form east of València. If this cluster indeed points towards the coast, heavy to excessive rain will be the main hazard.

... Sicily and parts of the Ionian Sea ...

A weak depression expands a bit to the east but otherwise remains more or less stationary during the forecast. Rich BL moisture results in 400 to 800 J/kg SBCAPE with scattered to widespread showers and thunderstorms. Shear remains weak with somewhat higher values towards Malta, where organized multicells could produce large hail next to excessive rainfall amounts. Otherwise, heavy to excessive rain will be the main hazard with slow moving storms. The area of main concern will be S-Italy, where the LL flow aligns parallel to the moisture axis with persistent diffluent flow atop (keeping the steering flow very weak). Training storms will be able to bring excessive rain to S-Italy with QPF up to 100 mm/24 h. Mainly the weak LLJ and the southward displaced moisture tongue keep us from upgrading to a level 2.
A few waterspout events are possible within the 15-% lightning area, as LLCAPE regionally exceeds 200 J/kg. The main limiting factors will be low mid-level CAPE (especially over the Adriatic Sea) for deeper and longer lived updrafts, weak convergence signals and increasing background flow. Nevertheless, on a local scale, conditions could be supportive for a few events.