dimanche 9 février 2014

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Sun 09 Feb 2014 06:00 to Mon 10 Feb 2014 06:00 UTC
Issued: Sun 09 Feb 2014 07:16
Forecaster: VAN DER VELDE
A level 2 was issued for Portugal and Spain mainly for severe convective wind gusts and tornadoes.

A level 1 was issued for Portugal, Spain and southern France mainly for severe convective wind gusts, excessive precipitation and tornadoes.


Three low pressure areas dominate the map. The Scottish low causes convective showers across a wide area from Celtic Sea to the Kattegat. Yesterday's active low over southwestern Europe is now weakening over Italy and the Adriatic Sea. It is replaced by a vigorously developing new Atlantic low affecting the Iberian Peninsula with stormy and rainy conditions. It develops a warm sector with ample moisture (9-10 g/kg mixing ratio below 1000m) and slight conditional instability under very strongly sheared wind profiles.

3 commentaires:

  1. ...Portugal and Spain...

    Models agree on a wide overlap of a few hundred J/kg CAPE and impressive vertical wind shear in all layers (e.g. 35 m/s 0-6 km shear and >17 m/s 0-1 km shear, >400 m²/s² 0-1 km and 0-3 km SREH (GFS model) with also very low LCL heights. This is highly supportive of mesocyclone and tornado development in thunderstorms, as well as bow echoes. Almost 1000 m²/s² 0-3 km SREH is forecast inside the warm sector where CAPE is not present. Instead, CAPE should develop in the region behind the mid level cold front which passes earlier than at low levels, creating a zone of warm humid low levels overspread by low theta-e mid levels and any lift in this potential instability region should result in development of conditional instability In this region the actual SREH for rightmoving cells is weak and for left-moving cells with respect to the mean wind is strong. The leftmoving motion vector would still have a southwesterly orientation. Mean winds aloft (1-3 km) reach over 30 m/s and may be transported to ground by deep convection. This is helped by the likely linear organization at the cold front, forced also by a deep potential vorticity intrusion.
    The episode should start during the afternoon in Portugal with probably some discrete supercells with a preference for leftmovers and take on more linear shapes over the southern half of Spain around 21Z when PV edge, surface and mid level cold front positions become collocated. Significant tornadoes may occur but severe convectively enhanced wind gusts should be more widely observed.
    The surface based CAPE in GFS seems to be reducing towards the east, turning into elevated CAPE. This may be due to the higher Saharan T850 advecting into southern Spain. It might stabilize the near-ground levels and reduce gust and tornado threat while maintaining the excessive precipitation threat which also is partly stratiform in nature, by the moist air advecting and lifting at high rates over local terrain.

  2. Weather warnings: Spain ,,,,,,,,,,,,,,,,,,,,http://www.meteoalarm.eu/index2.php?lang=en_UK&day=0&AT=0&country=ES

  3. Weather warnings: Portugal ,,,,,,,,,,,,,,,,,,,,,http://www.meteoalarm.eu/index2.php?lang=en_UK&day=0&AT=0&country=PT