Storm Forecast
Valid: Fri 27 Oct 2006 07:00 to Sat 28 Oct 2006 06:00 UTC
Issued: Fri 27 Oct 2006 07:12
Forecaster: DAHL

SYNOPSIS

Quite vigorous upper-level zonal flow is covering the northern parts of Europe ... with lifting lead vort max being associated with strong SFC low centered over the N Baltic Sea. Upper cut-off low is persisting over the W Maghreb States and the SW Iberian Peninsula. This overall pattern is not expected to change on Friday ... except that next ... comparatively weak ... Atlantic system will reach the British Isles late in the period. Quiescent SFC conditions should persist over central Europe and the Mediterranean regions.

DISCUSSION

... S Finland ... Baltic States ... Belarus ... extreme W Russia ...

Main focus for potentially severe convective evolution seems to exist along the cold front trailing from the Baltic SFC low. Scattered ... apparently strongly forced ... TSTMS have occurred along the front over the Baltic Sea last night. It seems that this activity may have been related to the vertical juxtaposition of the SFC front and robust DCVA-forced ascent ... which has now become increasingly separated per numerical analyses. This may affect the mesoscale-forced transverse frontal circulation which may be too weak now to sustain forced convection. It does not seem that weak late-October NE-European insolation will act to destabilize the low levels too much ... and an increase in TSTM activity during the day is not anticipated ATTM. However ... shallow/narrow line of forced convection could persist along the SFC cold front ... which may augment the LL winds. It seems however that this activity will become increasingly insignificant ... and a categorical risk should not be necessary.

... central France ... southern Germany ...

GFS hints at development of weak CAPE over central France and S Germany ahead of the SFC cold front. 00Z soundings do not suggest presence of any CAPE ... nor the presence of sufficient moisture or conditional instability ... and likelihood that widespread/significant CAPE develops today seems to be rather slim. But ... models advertise weak CAPE and convective precip ... which may be a result of moisture accumulation along the SFC boundary as a result of mesoscale UVVs ... which may be supported by DCVA-related ascent expected to overspread the region during the day.

DLS and LLS will be more than adequate for severe evolution once convection forms ... but given meager 00Z ascents ... threat appears to be quite conditional and neither a categorical risk nor a TSTM area will be issued for central France and S Germany ATTM. An upgrade may be required if thermodynamic fields improve more than what is currently anticipated.

... southern Spain ...

Indications are that TSTMS may be elevated given no SFC-based model CAPE where convective precip is simulated. Though LLS should be quite robust ... severe threat may be substantially reduced. If storms tap BL air however ... chance of an isolated tornado or two appears to exist. Threat should be too conditional for a categorical risk however.