Forecast Update
Valid: Thu 12 Apr 2007 18:00 to Fri 13 Apr 2007 06:00 UTC
Issued: Thu 12 Apr 2007 18:15
Forecaster: GATZEN

SYNOPSIS

See previous outlook

DISCUSSION

Northern Algeria

A dangerous situation has developed over northern Algeria. Very strong upper jet streak curving around the southern tip of the cut-off low over SWern Europe is directed towards northern Algeria. Winds reach around 45 m/s at the 300 hPa level, and strong DCVA is expected to persist underneath the cyclonic flank of this jet streak. At lower levels, an air mass characterized by a well-developed EML originating from the Sahara desert advects into central, and northern Algeria. Due to strong QG forcing and daytime heating, a strong surface low has formed over northern central Algeria. At the north-eastern flank of this low, strong south-easterly winds around 10 m/s continue to transport moist air mass from the southern Mediterranean into Tunisia, and Algeria. Latest surface observations indicate dewpoints up to 16°C over northern Algeria.

Latest satellite images show that intense, organized, and long-living convection has formed during the last hours. Expect that actual convection will go on during the night given persisting moisture advection from the east as well as QG forcing underneath the jet streak that propagates north-eastward. While most convective activity will likely spread north-eastward, merging into one or two MCS that move into Mediterranean during the night, some isolated cells may form over northern/north-eastern Algeria that will likely become supercells due to strong veering profiles. Latest GFS indicates around 30 m/s DLS as well as high helicity in the lowest kilometer.

While strong to severe wind gusts are forecast to be the most significant severe threat near the Mediterranean coasts, chance for large or very large hail increases further inland. Threat of tornadoes will increase during the evening hours when quite low LCL heights as well as increasing low-level vertical wind shear are forecast. Even strong tornadoes are not ruled out. Convective activity will spread into northern Tunisia in the morning hours, but weakening instability limits severe potential.