Storm Forecast
Valid: Mon 22 Sep 2008 06:00 to Tue 23 Sep 2008 06:00 UTC
Issued: Sun 21 Sep 2008 19:12
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 0600 UTC... a rather weak, but large mid-/upper-level low has its centre over eastern Alps. Several vorticity maxima rotate around its centre during the forecast period. At the surface, a bridge of high pressure connects an anticyclone over the Atlantic Ocean near 60N 20W with one at the same latitude near the Ural mountains. An inactive low pressure area moves slowly northeastward over the northern Black Sea while another weak cyclone travels eastward across the western Mediterranean.

DISCUSSION

Western Mediterranean, central and eastern Atlas...

Weak forcing associated with the advection of potential vorticity eastward across the region will likely prove sufficient for some renewed thunderstorm development across the Atlas mountains. It will probably sustain a couple of elevated storms across the Algerian coast and the western Mediterranean. 12 UTC soundings show that a well-mixed layer extends upward to around 750-700 hPa while low-level moisture is not as abundant as could be. Hence the highest MLCAPE values to be expected on Monday will probably not exceed 1000 J/kg by much. With 700 hPa wind of around 20 m/s, vertical shear however is strong, and storms that develop could become rather well-organized with main threats being downbursts and large hail. Storms should gradually weaken after sunset.