Storm Forecast
Valid: Tue 21 Dec 2010 06:00 to Wed 22 Dec 2010 06:00 UTC
Issued: Mon 20 Dec 2010 23:21
Forecaster: KOROSEC

A level 1 was issued for SW Spain, southern Portugal and coastal Marrocco mainly for excessive convective rainfall, strong winds and a few tornadoes.

SYNOPSIS

A large scale trough affecting much of west-central Europe with a surface SW-NE oriented frontal zone from southern Iberian Peninsula towards north-eastern Europe. A trough west of Iberia deepens as well as surface low when it approaches the peninsula. Another short-wave trough affects extreme southern Balkans during the day where mainly marginally organized convection (good instability, very low shear) will occur. Some stronger cells could support local flash floods over western Greece and Turkey, as well as having potential for a waterspout or two.

DISCUSSION

... SW Iberian Peninsula...

With deepening trough west of Iberian Peninsula, a surface cyclogenesis develops and slowly moves east during the forecast period. With SW flow ahead of it, warm advection continues spreading onto SW part of Iberian Peninsula, creating unstable and rather highly sheared environment beneath the strond mid-level jet surrounding the deep trough. Persisting flow will be favorable for continuous rainfalls onshore and combined with organized deep convective storms, local flash floods will be possible. Some of the storms may become severe given the favorable dynamics and could locally produce very intense rainfall as well as strong winds. It seems that LL shear and veering profiles could support a tornado or two as well. Strong forcing and persisting flow seem likely to support rapid clustering of the cells, so with combined training effect of the cells this could lead into enhanced flooding threat.