Storm Forecast
Valid: Fri 06 Dec 2013 06:00 to Sat 07 Dec 2013 06:00 UTC
Issued: Thu 05 Dec 2013 23:08
Forecaster: TUSCHY

A level 1 was issued for parts of C-Europe mainly for severe wind gusts. An isolated tornado event can't be ruled out.

SYNOPSIS and DISCUSSION

A 970 hPa depression over the Baltic Sea shifts east while filling a bit. No weakening of the intense gradient flow along its south/west quadrant is anticipated due to a still eastward building high pressure area over France.

For this period it will be hard to distinguish between severe wind gusts caused by the gradient flow itself and gusts with enhanced convection due to missing forcing mechanism.

In general, winds at 850 hPa remain in the 25 to 35 m/s range with a slow decrease during the overnight hours. Ongoing advection of a cold, well mixed but rather dry air mass is forecast, which should support downward mixing of those winds especially in the proximity of any shower/short-lived thunderstorm event. Only very meager and randomly shared SBCAPE signals in the model pool keep uncertainty high where to place any lightning area. Nevertheless, confidence in isolated thunderstorm activity is higher with organized bands of enhanced convection, emerging from the S-North Sea and the W-Baltic Sea and moving to the south/onshore. Bands of enhanced mid-layer vorticity, deep and near unidirectional wind profiles and a long fetch over SSTs of 10-13 °C (S-North Sea) and 8-11 °C (S-Baltic Sea) probably result in those anticipated banding structures. Sporadic but short-lived storms are possible with severe winds the main hazard. In addition, a southbound moving mid-layer impulse affects the S-Baltic Sea and Poland until noon, placed beneath the left exit of a potent mid/upper jet to the west. This feature could support a line of enhanced convection, moving southbound over Poland (W-E aligned and capable of producing a more concentrated swath of severe wind gusts).
Rising mid-layer heights should induce a gradual weakening trend of that activity from W to E. Although being a low-end risk, extreme SRH-1 may support a short-lived tornado event in case a stronger and more structured cell could evolve.

For the rest of Europe, no thunderstorm probabilities exist.