Valid: Sun 20 Nov 2016 06:00 to Mon 21 Nov 2016 06:00 UTC
Issued: Sat 19 Nov 2016 17:00
A level 1 was issued for S Italy and parts of C Mediterranean mainly for excessive precipitation.
SYNOPSIS AND DISCUSSION
The current Arctic anomaly results in much warmer temperature than average in high latitudes, while much cooler than average temperature remains over Asia, which is covered with an extended area of snow. An impressive ~1065 mb high pressure centre over N Kazakhstan influences E Europe. On the other hand, NE Atlantic experiences rapid cyclogenesis, which hits western parts of Europe on and on. A deep low pressure centre of 976 mb is expected to be passing over S U.K. by the morning hours on Sunday, heading Norway during the forecast period. Behind that, another cyclone develops and deepens, reaching Bay of Biscay further in the night. The pressure gradient between the high in the east and the lows in the west create strong southerly flow over much of the continent, advecting warmer air northwards in central Europe.
... Atlantic Coasts ...
Strong kinematics, with 15-25 m/s background low level flow, and strong synoptic forcing is forecast around N France and North Sea, where weak thermodynamics, barely reaching 150-200 J/kg MLCAPE exist. Given the storms form, they can linearly organize around the coasts, where the shear is higher compared to offshore North Sea. Severe wind gusts (up to 60-65 kts) will be the main risk over this area, but convection (even if exists) will play a relatively poor role enhancing it, therefore no threat levels are issued here. Later in the night, similarly low CAPE values approach Bay of Biscay and surroundings, with the upcoming cyclone. An isolated tornado is not ruled around NW Spain. Around Portugal, excessive nonconvective precipitation is a possibility.
... Mediterranean Sea ...
Regarding synoptic scale waves, the Mediterranean Sea, where most of the latent instability area exists, remains relatively calm, without strong gradients or patterns. Therefore, deep moist convection will be mostly unorganized with mostly less than ~10 m/s deep layer shear environments here. Up to ~1000 J/kg MLCAPE, PWs locally reaching 30 mm, system propagation vectors less than 3 m/s, and backbuilding kinematics may produce locally excessive precipitation around central Mediterranean, resulting in flash floods locally in S Italian coasts.