Storm Forecast
Valid: Tue 02 Mar 2010 06:00 to Wed 03 Mar 2010 06:00 UTC
Issued: Mon 01 Mar 2010 22:42
Forecaster: KOROSEC

A level 1 was issued for southern Portugal and extreme SW Spain mainly for large hail, excessive convective rainfall and lesser extent for tornadoes and strong winds.

SYNOPSIS

Two disturbances affect parts of Europe during the forecast period. First, a short-wave trough with a developing weak surface low over SE Balkans and northern Turkey. An attendant cold front will be a focus for convective development. Another trough/low, more pronounced disturbance takes place over SW-ern Iberian Peninsula as the intense vortex/upper low approaches from the west. Deep surface low with strong cold front is pushed towards southern Spain while strong subtropical airmass/warm front advects into the SW Mediterranean.

DISCUSSION

... SW Iberian Peninsula ...

Another surface depression takes place over the Iberian Peninsula during the day. Ahead of this low, strong subtropical airmass is advected northwards towards southern Portugal and SW Spain. Once the cool midlevels/steepening lapse rates overspread the warm sector, large scale lifting and marginal instability will lead into scattered convective development. However, a forced line of storms is as well possible just ahead/along the cold front. Shear up to 30m/s in the 0-6km layer and up to 20m/s in the lowest layers will favor organized storms. Locally, threat for excessive rainfall and large hail will exist. Given the easterly LL winds, enhanced SREH could yield in tornadogenesis, especially along the Iberian coast, but threat seems quite low attm.

Overnight on Wednesday, when vort-max moves more to the east, another surface depression forms in the left exit jet region over SW Mediterranean and a few storms will result. But given the uncertainities about the timing of this formation, a threat level was not extended more to the east. Although conditions may favour organized storms as well.

... SE Balkans towards NW Turkey ...

Models do agree in convective development along the SE-wards moving surface cold front during the first half of the forecast period, as the large scale ascent ahead of the trough overspreads the region. Weak instability signals but deep layer shear near 20m/s could be supportive for some stronger and organized storms, but both severity and coverage seem limited to warrant a threat level. However, locally excessive convective rainfall event with small hail cannot be completely ruled out.