Storm Forecast
Valid: Wed 17 Oct 2012 06:00 to Thu 18 Oct 2012 06:00 UTC
Issued: Wed 17 Oct 2012 04:18
Forecaster: PUCIK

SYNOPSIS

A very active period of severe weather in the Central and Eastern Mediterranean came to an end with the filling short-wave trough ejecting towards northeast during the day, detaching from the weakening frontal zone over the sea. Even though belt of strong mid-level lapse rates is forecast to stretch from Tunisia towards Greece/Turkey, yielding moderate latent instability, forcing factor will be largely missing and only isolated tstm activity in the weak flow regime is forecast. High geopotentials will begin building behind the trough with a high pressure system that is forecast to be centered over Romania by Wednesday afternoon.

Towards west, a significant mid/upper level trough is forecast over the Atlantic, amplifying towards south, with a deep low pressure system centered close to Ireland coastline, its trough stretching towards Western Iberia. Strong flow is forecast at the forward flank of the trough, yielding moderate to strong DLS over a wide swath of Western Europe. Poor mid-level lapse rates preclude significant instability in the warm sector ahead of the cold front, whereas poor low level moisture will limit the CAPE behind the cold front.

DISCUSSION

... Southeastern Ireland, Western England, Western Scottland ...

Close to the center of the deep low pressure system, strong low level flow, exceeding locally 20 m/s at 850 hPa should be observed over the area. At the same time, a left-exit region should pass over the region in the noon hours, providing enhanced lift and perpahs aiding in destabilisation. This should stay rather marginal due to the poor low level moisture and limited especially to the coastal areas. Enhanced DLS values should be observed especially in the eastern part of the area, underneath the strong mid/upper level flow. With low LCLs and strong background flow at low levels, isolated tornado in case that more pronounced / organised DMC manages to form is not ruled out, but threat seems to be too low to warrant a Level attm.

... Portugal, extreme SW Spain ...

A belt of marginal latent instability is simulated ahead of the progressing trough / cold-front which might feed some weakly electrified DMC especially towards evening/night hours. Particularly in the afternoon, an overlap of DLS and marginal instability is simulated over Portugal, but rather weak forcing should preclude any concentrated activity and severe threat should stay rather low.