Storm Forecast
Valid: Fri 12 Oct 2007 06:00 to Sat 13 Oct 2007 06:00 UTC
Issued: Thu 11 Oct 2007 22:12
Forecaster: DAHL

SYNOPSIS

Broad and strong early-fall upper westerlies have established over the northern parts of Europe. An imbedded trough located over the Baltic Sea at the beginning of the period will dig into SE Europe by Saturday morning and thereby merge with a weak elongated upper low over the western and central Mediterranean. As a result, an upper cut-off cyclone will be left from the latter feature over the western Iberian Peninsula late on Friday. Rather intense low-level cyclone is attendant to the digging Baltic upper trough, but will slowly weaken on its eastward track across the Baltic States on Friday. The associated polar air at its western periphery will intrude into the eastern portions of central Europe.

DISCUSSION

... south-central Mediterranean Sea ...

It seems that an EML advecting eastward off the Atlas mountains will result in reasonable CAPE over the south-central Mediterranean Sea given about 10 g/kg mean-layer mixing ratios underneath the EML. Some DCVA should be in place, so that a continuation/itensification of the convective activity is anticipated. Deep shear should be on the order of 20 m/s, suggesting that a few severe storms will be possible. Severe-weather threat should spread eastward during the period, as it will be tied to an eastward-moving upper speed/deep-layer shear maximum. Supercells and well organized multicells will likely occur, capable of severe wind gusts and large hail. LLS is somewhat weak, so the tornado threat does not appear to be extraordinarily high, though a brief spin-up could not be discounted.

... Baltic Sea ...

Very steep low-level larpse rates are simulated to develop over the Baltic Sea in the fresh polar air. However, rather strong flow could be detrimental to waterspouts given increased turbulent mixing and an associated depletion of low-level lapse rates, and possibly impeded formation of mesoscale boundaries that may serve as source of vorticity. Also, rapidly rising SFC pressure/subsidence courtesy of strong low-level cold advection will likely limit the depth of convective mixing ... so that allover threat for waterspouts should be comparartively low despite the steep low-level lapse rates in the GFS solution.