Storm Forecast
Valid: Mon 10 Jan 2011 06:00 to Tue 11 Jan 2011 06:00 UTC
Issued: Mon 10 Jan 2011 05:00
Forecaster: DAHL

No threat levels issued.

... SYNOPSIS ...

A meandering upper westerly flow is present over Europe, with a southern-stream upper trough extending into the Mediterranean, which is making slow eastward progress. An upper jet streak will cross western France late Monday night. This feature will be accompanied by a SFC low traveling from the British Isles into the North Sea by the end of the period. Rather quiescent synoptic SFC conditions will prevail over the Mediterranean regions.


... DISCUSSION ...

... central France ...

The jet streak crossing western France late in the period will provide ascending motion, while especially low-level shear as well as low-level moisture will also be in place. GFS and WRF hint at weak CAPE that could develop ahead of the jet streak. However, the depth of the unstable layer is uncertain. Given that the jet-streak velocity and ist gradients are not extraordinarily strong, and the weak signals in the models, confidence is rather low that convection will indeed form. If it did form, it would probably be strongly forced, leading to a rather shallow linear system, capable of strong wind gusts and possibly also a brief tornado or two. However, the severe probabilities are well below the LVL1 threshold.

... extreme western Iberia ...

Convection will likely exist off the Iberian west coast on Monday ... and dacay as it makes landfall. However, along the coast there will likely be a region where CAPE is still strong enough to sustain the convection, but where at the same time frictionally-enhanced low-level shear exists. This suggests that there exists a slim chance of briefly rotating updrafts that could potentially spawn a brief tornado. However, the small spatial window in which the storms would have to become mesocyclonic, and the overall weak instability suggest that the severe threat is rather limited and a LVL1 threat does not seem necessary at the moment.

... central Mediterranean regions ...

Convection will likely persist over the central Mediterranean ahead of and beneath the eastward-migrating upper trough. CAPE and shear should be weak throughout the region, so that the organized severe threat should be very low. However, an isolated waterspout or two seem to be possible over the western portions of the Mediterranean and, late in the period, also over the Adriatic Sea.