Storm Forecast

Storm Forecast
Valid: Mon 13 Oct 2014 06:00 to Tue 14 Oct 2014 06:00 UTC
Issued: Sun 12 Oct 2014 23:09
Forecaster: PUCIK

A level 1 was issued for W Iberia mainly for excessive precipitation.

A level 2 was issued for the Ligurian Sea and parts of N Italy mainly for excessive rain, (very) large hail, severe wind gusts and tornadoes.

A level 1, surrounding Level 2, was issued for excessive rain, severe wind gusts and large hail.

A level 1 was issued for S France mainly for excessive precipitation.

A level 1 was issued for NW Germany mainly for severe wind gusts and marginally large hail, to the lesser degree for tornadoes.


Major macrosynoptic feature will remain in the form of a large trough over the Atlantic. Several short-wave troughs are associated with it, rotating around. Strong southwesterly flow on its forward flank is forecast to decrease during the forecast period. Towards east, a ridge will stretch from Tunisia towards S Poland. A cut-off low is situated over Turkey, slowly filling in.


... W Iberia ...

A sharp short-wave will drop towards Iberia during the forecast period, located at the left exit region of 70 m/s jet-streak. In the warm sector of the associated frontal system, models simulate marginal latent instability, linked to the tongue of moister airmass. Significant forcing from the trough, along with the coastal and orographic uplift will provide for a likely heavy precipitation event over a large area. Convection may well contribute to the resultant rain sums, especially close to the coastline with possibility of training event. Lvl 1 is thus warranted for excessive precipitation. A band of heavy precip will translate SE-wards during the day.

... Ligurian Sea, N Italy ...

Ahead of the approaching short-wave trough, 20-25 m/s of S to SW 500 hPa flow is simulated by the models, decreasing during the second half of the forecast period. Southerly flow closer to the surface will continue advecting very moist airmass, with coastal Td readings above 20 deg C. Especially over the sea, moderate to high CAPE values are simulated with a tongue of instability reaching directly into the Gulf of Genoa. Very pronounced overlap of high latent instability and moderate to strong vertical wind shear is forecast over the Ligurian Sea and associated coastlines. As such, well organised DMC, including supercells, will be possible, with threats of (very) large hail, damaging wind gusts and even tornadoes (due to the enhanced LLS). However, it still seems that the dominant threat will be excessive precipitation. With abundant low level convergence, large MCS will be likely with training pattern near the coasts. Lvl 2 is introduced for an area, where the combination of all mentioned threats will be present. MCS may be already ongoing in the beggining of the forecast period, shifting E and SEwards during the forecast period.

... NW Germany ...

A plume of moderately steep lapse rates (around 7 K/km in the 800-600 hPa layer) will be advected from the south, contributing to the development of CAPE values on the order of hundreds J/kg. Presence of 500 hPa flow around 20 m/s will contribute to the DLS values between 15-25 m/s, conducive for well-organised DMC. Scattered DMC is forecast to initiate south of the advancing warm front, while some of the cells may attain supercellular characteristics. In that case, severe wind gusts as well as marginally large hail may occur. Tornado threat is not discounted either, but LLS should be rather limited (values at or mostly below 10 m/s). The highest threat will exist between 12 and 15 UTC.

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