Valid: Fri 21 Feb 2014 06:00 to Sat 22 Feb 2014 06:00 UTC
Issued: Thu 20 Feb 2014 23:11
A level 1 was issued for Crete and the far S-Aegean Sea mainly for an isolated excessive rainfall event, isolated large hail and a few waterspouts. The level 1 was stretched far west to include a large hail risk over the SE Ionian Sea and extreme S-Greece.
SYNOPSIS and DISCUSSION
The steering mechanism is a filling and vertically stacked vortex north of Scotland. Brisk westerlies overspread NW Europe, as numerous embedded short waves cross Ireland, UK, N-France, Benelux and parts of N/C-Germany from west to east. Mid-levels remain cold and steep mid-layer lapse rates atop a seasonally mixed marine layer offer some low-end SBCAPE build-up. Marginal LLCAPE and augmented LL speed/directional shear could cause an isolated funnel/short tornado event mainly along westward facing coasts of Ireland and UK. Gusty winds and sleet/isolated marginal hail accompany stronger storms. The activity wanes during the late afternoon hours.
Already advanced time of year with temporal sunshine offer enough diabatic heating for some diurnal driven shower/isolated thunderstorm activity over parts of N/C France, Benelux into NW Germany. A 500 hPa speed maximum over C-Germany should induce somewhat higher thunderstorm probabilities over NW Germay to far S-Denmark. Sleet/marginal hail and gusty winds will be the main hazard although an isolated funnel event in this weakly sheared air mass can't be excluded. This activity wanes during the late afternoon hours but could continue until the evening hours over extreme N-Germany/S-Denmark.
A weakening upper trough over the Ionian Sea and a dissolving surface depression cause scattered shower/thunderstorm activity over a vast area. MLCAPE up to 1000 J/kg will be robust due to a cold lower/mid troposphere over 17-19 °C SSTs. Most of the time, shear/CAPE remain well separated ... excluding Crete during the overnight hours, where 10-15 m/s DLS probably causes a few better organized multicell events. Slow storm motions could yield an heavy rainfall risk and the mesoscale dictates a regionally enhanced waterspout risk. That's why Crete and far S-Aegean Sea were upgraded to a level 1. That level 1 was stretched far west to the SE Ionian Sea for an augmented large hail threat with intense pulsating storms. This also includes far S-Greece.
Quiet conditions persist over E/NE Europe as 1020 hPa high remains in place.