Storm Forecast
Valid: Fri 02 Jan 2009 06:00 to Sat 03 Jan 2009 06:00 UTC
Issued: Thu 01 Jan 2009 16:17
Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

The quiescent weather in consideration of electrified convection continues for the following forecast period. A cold and dry airmass floods N/E and central Europe. Convection will be enhanced mainly over surfaces of the weater, where the fetch offshore is adequate for enough moistening of the lower levels, but there are no indications that any area will see enhanced chances of electrified deep convection beside a small swath over Estonia/Latvia. Hence there are only two areas to look at:

... S of Italy and Tyrrhenian Sea after sundown ...

As mid-levels start to cool down during the evening hours, warm SSTs result in SBCAPE in the order of roughly 500 J/kg. The atmosphere remains only weakly capped during the night hours, so deep convection would be possible, but there are no clear signs of convergence zones. We don't go with models, which show an extensive area of convective precipitation and only highlighted areas with highest instability and near zero capping. Climatology was included in final consideration of the thunderstorm risk. However, the risk of a very isolated thunderstorm event beyond the highlighted areas won't be zero.

... Portugal and west of the Strait of Gibraltar ...

Better convergent signals would help to pinpoint potential thunderstorm hot spots as atmosphere remains at least weakly capped over Portugal and also to its west and south. Parts of Portugal see a prolonged period where at least isolated thunderstorms are likely, one during the afternoon/during the passage of an ill defined cold front/and one during the night hours along the path of the cold upper low. A low energy/weak shear environment keeps the severe risk marginal, although gusty wind and marginal hail are possible. A very low end large hail risk arises during the morning hours(SAT,01.03) over extreme SW Portugal just at the base of a cyclonical curved upper jet, but timing and environment argue against the issuance of a level area.

Models spread convective signals well inland and also south of Portugal and the Strait of Gibraltar, but either instability decreases too fast inland or atmosphere remains too warm and attendant weak lapse rates limit stronger updrafts. We decided to issue a general thunderstorm area just west of the Strait of Gibraltar, due to very low EL temperatures,approaching faint cold front from the WNW after 00Z and tie to nice theta-e tongue, characterized by modified subtropical air. Nothing severe forecast.