Storm Forecast
Valid: Mon 10 Nov 2008 06:00 to Tue 11 Nov 2008 06:00 UTC
Issued: Mon 10 Nov 2008 05:59
Forecaster: SCHLENCZEK
SYNOPSIS
An intense low pressure complex is present between Scotland and Iceland. The associated surface low will weaken during the period whereas the upper trough will dig southeastward. The cold front stretches from northern Iberia via France to southern Norway and will move southeastward. In the vicinity of a 70 m/s upper jet streak over southern UK, a baroclinic wave is simulated by global NWP models. As the background flow and the frontal boundary are almost parallel, rapid cyclogenesis is not expected with that wave. The wave will enter western Europe during the afternoon.
A weak upper low over the central Mediterranean will translate eastward during the period. Showers and thunderstorms are forecast over the central Mediterranean and the Aegean Sea.
DISCUSSION
...SW UK, Channel region, NW France...
Recent soundings of Brest and Camborne show some low-end instability in the lowest 3 km. Low level shear in order of 20 m/s and up to 45 m/s deep layer shear are expected in the region discussed here. A small speed max with 35 m/s at 850 hPa will cross northwestern France during the afternoon. Strong QG forcing will be provided by an intense upper vort-max that overspreads the region in the late afternoon. GFS does not predict sufficient instability but a shallow convective line with severe convectively-enhanced gusts may develop. At the moment, thermodynamics should be too hostile for organized severe convection and a threat level is not issued.
...S Norway...
The cold front will cross the region in the next few hours. Some low-end instability is forecast and low level shear is locally enhanced. Isolated severe gusts are not ruled out but instability is forecast to decrease in the next hour which limits the threat of severe gusts.
...Central Mediterranean...
Some hundred J/kg of CAPE are present over the central Mediterranean and Aegean Sea. Weak vertical shear should preclude organized convection but low LCL heights may allow an isolated waterspout.
