Storm Forecast
Valid: Tue 01 Nov 2016 06:00 to Wed 02 Nov 2016 06:00 UTC
Issued: Mon 31 Oct 2016 22:41
Forecaster: DAFIS
A level 1 was issued for the coasts of NE Netherlands, NW Germany and W Denmakr mainly for severe wind gusts.
A level 1 was issued for the North Turkey mainly for excessive precipitation.
A level 1 was issued for the SW Portugal mainly for excessive precipitation and marginal severe wind gusts.
SYNOPSIS
A ridge over West Europe brings warm air masses from Mediterranean basin up to the UK. A low pressure system is found west of the Iberian Peninsula and its frontal activity will affect Portugal on Tuesday, another one is forming over Norway - Sweden and several short-wave troughs circle the wide ridge, with two of them will being responsible for marginal convective activity. One is moving over the North Sea and the other one is crossing the Black Sea towards North Turkey. Outside of our domain, Cyprus will experience some heavy downpours as well as the coasts of Libya.
DISCUSSION
.... NE Netherlands, NW Germany, W Denmark ....
The S-SE-ward moving cold front of the cyclone over South Scandinavia will result in several convergence zones near the coasts, where moist marine layer will be pushed on land further to the south. The first half of the day we expect a fast moving non-convective rain band but as a mid-level impulse/IPV anomaly crosses the North Sea after 18z, we forecast isolated to scattered showers or thunderstorms with some of them becoming longer lived or severe in terms of wind gusts. CAPE on maps is marginal and less than 400 J/kg but enhanced DLS (20-30 m/s) could assist some cells to become organized and if 0-3 km shear verifies, several strong to severe wind gusts are expected. Tornado threat is limited due to high LCLs but a few waterspouts may form as LLS over the sea reaches 10 m/s overlapped with some CAPE after 18z.
.... N Turkey ....
More or less same conditions are expected for North Turkey as cold air masses will move over the Black Sea and destabilization will lead to some marginal thunderstorm activity off shore during the morning. Steep orography of North Turkey is expected to enhance the lift of air masses on shore and some more organized clusters will be able to produce excessive precipitation before 15z. High resolution, GFS-driven models (WRF-BOLAM) produce about 50mm of convective precipitation in 12 hours. Given the SST-850 hPa temperature difference of more than 12°C and some marginal LLS, waterspouts cannot be ruled out.
.... SW Portugal ....
The quasi-stationary low pressure system west from the Iberian Peninsula pushes warm and moist marine air masses over Portugal. Global NWP models predict about 1-1.5 kJ/kg MLCAPE and DLS in the range of 10-15 m/s. A persistent low level flow from the southwest could lead to excessive precipitation events in the west-ward coasts of the country, partly convective. Finally, a gradually strengthening DLS during the night and elevated CAPE can produce storms with some strong wind gusts.
