Storm Forecast

Storm Forecast
Valid: Sat 17 Nov 2018 06:00 to Sun 18 Nov 2018 06:00 UTC
Issued: Sat 17 Nov 2018 00:42
Forecaster: BEYER

A level 1 was issued for the southwestern coastal areas of Turkey mainly for excessive precipitation and to a lesser extent for large hail, severe wind gusts as well as tornados.


A strong upper level high with corresponding surface high is influencing large parts of Europe. Supported by strong WAA on the forward flank of a highly amplified trough over the North Atlantic Ocean, the center of the high is moving northward during the forecast period. On its southern flank, very dry air masses are advected from Western Russia into Central Europe, prohibiting any DMC. The same is true for Northern Europe mainly due to the strong sinking caused by the high.

At the same time an upper level low, which is almost not visible at lower levels, moves westward on the southern flank of the high and thus influences most parts of the Mediterranean with unstable air masses.
At the end of the forecast period, it connects with a low that is pinched of from the highly amplified trough just west of the Iberian Peninsula.


... The Mediterranean ...
Unstable conditions combined with enhanced specific humidity lead to the build-up of a few hundred of J/kg of CAPE. Several regions of persistent moisture flux convergence can be anticipated that should lead to somewhat enhanced CAPE values and can combine with rather strong DLS (0-6 km 20 to 30 m/s). The result should be a persistent thunderstorm activity in that regions. One area can be found west of Sardinia and another even more pronounced one in the Ionian Sea. They are supposed to not influence any land. Therefore we did not issue any threat level for this.

... SW coast of Turkey ...
With a southerly LL flow, strong moisture convergence just off the coastline of SW Turkey is forecasted to persist throughout most of the forecast period. The exact region of strongest convergence remains almost stationary. In that region a maximum of moisture can be found, combining with steep lapse rates to about 500 J/kg of MLCAPE.

Persistent and almost stationary thunderstorm activity in that region may locally lead to excessive precipitation.
In addition, strong DLS can be found with values of more than 20 m/s. This implies a better organization of the storms posing the risk for large hail. However, only modest values of CAPE reduce that risk.

In the same region also SRH0-3 shows enhanced to strong values. LLS shear has locally values of more than 10 m/s and forecast soundings show a nice veering of the vertical wind profile in the lowest layers.
Taking this together a few supercells may form that locally can also bring severe wind gusts. Having in mind low LCLs the occurrence of a tornado cannot be excluded.

... Portugal ...
A cold front of a surface low west of the Iberian Peninsula is reaching southern Portugal during the night hours. It can be anticipated by a strong maximum in moisture convergence. A few hundred J/kg of CAPE are forecasted to build up. Therefore several storms should form along the cold front. They may locally lead to excessive precipitation as well as strong wind gusts. However, the overall threat is forecasted to be not high enough to issue a level 1.

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