Storm Forecast
Valid: Wed 03 Mar 2010 06:00 to Thu 04 Mar 2010 06:00 UTC
Issued: Tue 02 Mar 2010 22:51
Forecaster: PUCIK

SYNOPSIS

A composite weather pattern is shaping up over Europe. A shallow pool of low geopotentials is prominent over Western Europe with a cyclonic vortex at its southern end, which is expected to slowly fill on its progress over Iberia. To the northeast a deep low, centered over Southern Finnland and filled with arctic maritime airmass will influence the weather over Northern, Eastern and partly also Central Europe. Strong jet, streaming close to the base of this low will couple with a subtropical jet over the Southern Mediterranean. As an interesting note, a high pressure system is expected to start building up over the Eastern Atlantic and this feature will likely influence the course of the synoptic situations over the next few days.

Predominantly unfavorable conditions for deep moist convection are forecast over Europe, except for the western half of the Mediterranean and a coastline area of Portugal. Low topped convection with very sporadic lightning might be observed in a cold and moist fresh northwesterly flow around the aforementioned low, mainly in the belt from Ukraine to the Black Sea. Models simulate around 100 J/kg of CAPE in this area, along with very low moisture content and because of that reason, lightning area is not issued at the moment.

DISCUSSION

...Southwestern Iberia, Northern Morocco...

A shortwave trough will rotate around the larger scale cyclonic vortex and on its forward flank, upward motion is simulated, likely contributing to the destabilisation. Models simulate marginal instability built-up, with MLCAPEs in order of 500 J/kg. With the approach of the surface low, strong flow at lower tropospheric levels is simulated, with up to 25 m/s at 850 hPa level. Subtropical mid and upper level jet should be displaced more to the south, however, and therefore, strong wind shear will likely stay confined to the lowest km or two. This will likely be a detrimental factor concerning the organisation of the storms. Low level shear will for sure exceed values of 10 m/s with moderate values of SREH, probably reaching 100-150 J/kg in the lowest km. Due to this fact, low end tornado and severe wind gust threat will probably exist, but the overall risk does not seem to warrant a Level 1.

... Western Mediterranean to the western coast of Italy...

As the surface low will lift from the coastline of Algeria towards Italy, a strong warm air advection is likely at its forward flank. Prominent isentropic lift to the north of the warm front will contribute to the generation of large stratiform precipitation shield. Directly behind it, an elevated instability is simulated, especially apparent from ICAPE and MUCAPE fields. Despite the fact, that high values of bulk wind shear are forecast over the highlighted area, severe weather threat will be very low, mainly due to the fact, that instability will only be marginal and at the same time, most of it likely not rooted in the boundary layer.