Storm Forecast
Valid: Mon 10 Mar 2008 06:00 to Tue 11 Mar 2008 06:00 UTC
Issued: Sun 09 Mar 2008 19:16
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00 UTC, the core of a deep, mature surface low with a central pressure near 950 hPa is expected over NWrn Ireland and moves slowly ESEward. A strong, 80 m/s northwesterly jet has it left exit region over western parts of the English Channel. A weak mid/upper tropospheric trough over the western Mediterranean moves eastward during the period. Early on Tuesday morning a new frontal system is expected to approach the Biritsh Isles from the west.

DISCUSSION

Southern England, Western France...

The primary cold/occluding front of the strong cyclone over Ireland is expected near a line from Bristol to Brest at 06:00 UTC. AFWA MM5 maintains a narrow area of CAPE ahead of the frontal zone during the day, whereas GFS does not indicate any. Current thinking is that a convective line will be present along the surface front before weakening in the early afternoon as forcing for upward motion becomes weaker as the jet moves on to the southeast.

The passage of the frontal convective line will be accompanied with severe gusts. Given that the line's inflow should contain high streamwise vorticity, the development of rotating updrafts is not ruled out. A small threat of tornadoes will therefore exist.

SW Ireland...

Early Tuesday morning, Ireland will likely be affected by the next frontal system. The associated warm sector is filled with moist air with dew points of 8 C and higher. Some convection is consistently being modelled near the occlusion point that, as is often the case, is located under a jet streak's left exit region. High values of storm-relative helicity and strong low-level shear are modelled, so that the development of a shallow rotating storm is possible with a small attendant threat of a tornado.

Central Mediterranean...

Isolated to scattered thunderstorms are likely ongoing near the axis of a mid/upper trough west of Corsica and Sardinia. The trough moves eastward during the day, reaching the Ionean Sea on Tuesday morning. The focal point of the attendant convective activity is expected to translate eastward as well through the indicated area. The convection will be able to access around 500 J/kg CAPE and develop within a moderately-sheared environement (around 15 m/s 0-6 km deep layer shear). As a result, the storms may become relatively well-organized multicells. Weak CAPE and forcing, however, appear to limit the severe weather to gusty winds and some, mostly small hail.

SE Balkans, NW Turkey...

A trough over Greece is expected to accelerate eastward. DCVA related upward motion ahead of the system will likely create around 500 J/kg CAPE available for release in subsequent convection. Weak to moderate vertical shear and low CAPE however preclude the issuance of a threat level for this area.