Storm Forecast
Valid: Wed 15 Oct 2014 06:00 to Thu 16 Oct 2014 06:00 UTC
Issued: Tue 14 Oct 2014 20:41
Forecaster: PUCIK
A level 1 was issued for Portugal mainly for excessive precipitation.
A level 2 was issued for parts of central Italy and the Adriatics mainly for large to very large hail, excessive precipitation and to the lesser degree for tornadoes and severe wind gusts.
A level 1 surrounding level 2s was issued mainly for excessive precipitation, large hail and to the lesser degree for tornadoes and severe wind gusts.
A level 1 was issued for SW Hungary and E Croatia mainly for marginally large hail and marginally severe wind gusts.
SYNOPSIS
Satellite loops reveal major low pressure system centered over the Atlantic, which will further reinforce WAA over much of Europe in the following days. Beyond this low, situation over Europe is quite diverse with numerous disturbances embedded in the zonal flow.
Quite active pattern will continue especially over the Mediterranean, namely Italy and the Adriatics, where soundings reveal presence of steep lapse rates and at the same time, moderate to strong vertical wind shear.
DISCUSSION
... N France towards BENELUX and W Germany ...
Behind the occluding front, an airmass characterised by steeper lapse rates will be advected from west towards the region. The best forcing will be available overnight from Wednesday to Thursday in the left exit zone of the jet streak. However, at this time, instability will likely be elevated, reducing the risk of severe wind gusts or tornadoes despite the presence of strong low level wind field. Thus, no lvl is introduced atm.
... Portugal ...
In the WAA over the region, continuous uplift of the air parcels along the coastline should result in the repetitive regeneration of convective cells. Moist airmass, characterised by mixing ratios of about 12 - 14 g/kg will be only marginally unstable due to the lack of steep lapse rates. Nevertheless, this may be still be sufficient for convection contributing to the heavy rainfall event, worthy of a Lvl 1.
... Central Italy towards the Adriatics ...
Southerly surface flow will continue to advect moist airmass to the north, overlaid by an EML originating from N Africa. Combination of steep lapse rates and moist boundary layer will again prove sufficient for moderate to high CAPE values. Furthermore, about 20 m/s of 500 hPa flow with southerly flow at the surface will ensure strong directional and speed shear, sufficient for well organised multi and supercellular convection. In case of supercells, large to very large hail, severe wind gusts and even tornadoes will be possible. Furthermore, due to the presence of very moist airmass and possibility of cell training, localised very excessive precipitation events will be possible. Small Lvl 2s were issued for the regions, where the combination of the threats may attain the greatest coverage. As mid-level temperatures rise towards the evening and flow deccelerates, conditions for severe DMC will quickly deteriorate.
... SW Hungary, E Croatia ...
Ahead of the approaching short-wave, southwesterly flow will advect part of the EML plume, contributing to the destabilisation. Surface heating may be hindered by an abundance of low to mid level clouds originating from the convective clusters over the Mediterranean. DMC will form in the environment of 15 - 20 m/s of DLS. In combination with the steep lapse rates, well organised cells may be capable of marginally large hail or severe wind gusts. A conditional Lvl 1 is introduced for this area.
