Storm Forecast
Valid: Thu 05 Apr 2007 07:00 to Fri 06 Apr 2007 06:00 UTC
Issued: Thu 05 Apr 2007 07:25
Forecaster: GATZEN

SYNOPSIS

Strong arctic trough over Scandinavia supports cold air advection into north-eastern Europe. To the south, a rather strong frontal boundary is present from the North Sea to southern Scandinavia and further to western Russia. Rather warm air mass remains in the range of a weak ridge that stretches from a high over British Isles to northern Balkans. South of the ridge, low geopotential present over Mediterranean weakens during the period. A cut-off is forecast to remain over southern Iberian, while a short-wave trough over eastern Mediterranean moves into Black Sea region. At lower levels, only weak instability is present over most of Mediterranean, where low clouds may also inhibit insolation over most places. Weak forcing and vertical wind shear are also expected and chance for severe thunderstorms is forecast to be low. Vertical profiles seem to be more interesting over the southern regions of the Mediterranean.

DISCUSSION

Southern Mediterranean

A tongue of low-level instability has developed over southern Mediterranean as indicated by a few soundings. Steep low-level lapse rates as well as rich boundary-layer moisture are present especially near southern Iberian Peninsula and southern Italy. Today, some vort-maxima/jet streaks are forecast to move eastward, affecting southern Iberian Peninsula as well as Sicily. While regions with moderate deep layer wind shear and deep instability are not expected to overlap, some QG forcing will likely affect those regions. Showers and thunderstorms are forecast to develop. Given rather strong low-level buoyancy and almost no CIN, a few waterspouts are forecast to develop. Increasing DLS over southern Iberian Peninsula in the range of propagating short-wave trough/jet streak may increase the chance for a few organized storms, capable of producing locally hail and strong wind gusts. As vertical veering is not expected to be favorable for mesocyclones, tornadoes or large hail seem to be unlikely.

Turkey

In the range of strong south-westerly jet, strong to very strong vertical wind shear will affect most of Turkey during the period. Approaching vort-max over Aegean/Black Sea will likely provide DCVA, and QG forcing is forecast to go on. Although weak instability is forecast by latest models and sounding over Istanbul indicates an EML above the dry boundary layer, chance for thunderstorms is weak over most places given lack of diurnal heating due to low clouds. Current thinking is, that a few mostly embedded thunderstorms will form during the day. Best potential seems to exist over the central regions where QG forcing will be strongest as well as over the southern mountains, where upslope flow is expected. Chance for a few supercells is not too high, but will not exclude some reports of large hail, severe wind gusts and also isolated tornadoes. Due to many limiting factors (stratiform clouds, weak forcing), we do not issue a level 1 ATTM. However, the situation has to be monitored closely.