25-08-2015 22:09 | Estofex | m.b.t. 26-08-2015 t/m 27-08-2015
Storm Forecast
Valid: Wed 26 Aug 2015 06:00 to Thu 27 Aug 2015 06:00 UTC
Issued: Tue 25 Aug 2015 22:09
Forecaster: PUCIK
A level 1 was issued for BENELUX and extreme NW Germany mainly for severe wind gusts and tornadoes.
A level 1 was issued for Algeria and Tunisia mainly for large hail and severe wind gusts.
SYNOPSIS
Synoptic situation will be dominated by an extensive low pressure system centered over the Atlantic with strong prevailing flow at its southern and eastern flank. A ridge will stretch from the Mediterranean into Central Europe with lower geopotentials to the east over Russia. Several areas may see isolated to scattered DMC with the most interesting areas being BENELUX ahead of the cold front and N Africa with diurnally driven thunderstorms especially close to the mountains.
DISCUSSION
... BENELUX, extreme NW Germany ...
Ahead of the advancing cold front, WAA regime at lower troposphere is forecast over the area in the afternoon hours. At the same time, mid-tropospheric temperatures will remain the same or drop slightly, increasing the lapse rates. With dewpoints around 14 deg C, modest CAPE values are forecast, likely not exceeding 500 J/kg. At the same time, strong vertical wind shear is forecast with values around 20 m/s in the 0-3 and 0-6 km layer and values over 10 m/s in the 0-1 km layer. Furthermore, WAA regime will contribute to veering wind with height and SREH 0-3 km may exceed 300 m2/s2. Such vertical wind profile certainly favours well organised DMC, including supercells, even though linear segments may be more preferred as wind shear is confined to the lower troposphere. DMC will be initiated by the frontal boundary with no obvious short-wave at the mid or upper troposphere.
Basically two scenarios are possible in the situation:
1/ In case that instability will eventually materialize, well organised DMC may be capable of isolated severe wind gusts and/or tornadoes, with the greatest threat around 18 UTC.
2/ In case that instability does not support strong enough updrafts, only disorganised showers and/or weakly electrified tstms may not produce any severe weather.
Lvl 1 is introduced for the region covering the first scenario with isolated severe weather.
(alleen de voor NL en aangrenzende streken relevante tekstdelen overgenomen, klik hier voor de volledige forecast, red.)
Verwachtingen/waarschuwingen
