Storm Forecast
Valid: Sat 25 Sep 2010 11:00 to Sun 26 Sep 2010 06:00 UTC
Issued: Sat 25 Sep 2010 11:03
Forecaster: VAN DER VELDE

A level 1 was issued for the eastern Adriatic and northern Aegean Sea coasts and mainly for excessive convective precipitation.

SYNOPSIS and DISCUSSION

A large-scale (mid level) low pressure area covers Europe and advects a warm moist airmass northward into the Balkan and Central Europe while cool drier air is advected southward into Western Europe. A cold front passing the Adriatic Sea during the early evening will invigorate convection which can stick to the coastline for some time due to strong convergence and orographic lifting, while saturated profiles, slow cell motion and high precipitable water content favor high precipitation efficiency and therefore a chance of local flash floods. Waterspouts are not ruled out and SREH values around 250 m²/s² could induce storm rotation (supercells) although low level shear and weak lapse rates appear insufficient for a significant tornado and hail chance, respectively. Limiting is also MLCAPE (1000m mixed)with values predicted mostly under 500 J/kg.

A smaller secondary low swings around the large one from Denmark to Belgium with some CAPE over sea and EL (cloud tops) cooling during the night to below -20°C. There is a strong PV anomaly associated with this low which will remain recognizable for the following few days as it slowly moves over France towards northern Italy.