Storm Forecast
Valid: Sat 13 Feb 2016 06:00 to Sun 14 Feb 2016 06:00 UTC
Issued: Fri 12 Feb 2016 21:31
Forecaster: TASZAREK
A level 1 was issued for N Portugal, Spain portion of France and Balearic Islands mainly for the severe wind gusts and in lesser extent for tornadoes.
A level 1 was issued for N Portugal mainly for the excessive precipitation.
A level 1 was issued for E Adriatic and E Ionian Sea mainly for the severe wind gusts and excessive precipitation.
A level 1 was issued for E Aegean mainly for the severe wind gusts and excessive precipitation
A level 1 was issued for CNTRL France mainly for severe wind gusts
SYNOPSIS
Most of the N and CNTLR Europe is covered with a polar dry air mass where due to absent thermodynamic instability convection is unlikely. A wide jet stream stretches from N Atlantic through Iberian Peninsula, CNTRL Mediterranean and Turkey. Within this flow, a few shortwaves are forecast to produce high shear/low cape conditions where severe convective storms will be possible. In the end of the forecast period, a long wave over Iberian Peninsula will amplify and bring and advection of the cold air mass.
DISCUSSION
...Iberian Peninsula, Balearic Island...
A shortwave is forecast to enter W part of the Iberian Peninsula in the afternoon hours and propagate eastwardly to reach Sardinia and Corsica in the end of the forecast period. Although a thermodynamic instability over the land surface will be small and produce mostly low-topped convection, a NWesterly advection of PV units and a significant airflow in mid and low troposphere may organize thunderstorms into low-topped mini supercells capable of producing severe wind gusts. It is worth to mention that vertical profile of the wind field (0-1km SRH locally up to 400-500 m2/s2) and moist boundary layer (mixing ratio up to 8-9 g/kg) will be conducive for the tornado occurrence. Therefore an isolated tornadic event cannot be ruled out, especially in the NW part of the Iberian Peninsula where the conditions are the most promising. A superimposing stratiform precipitation with the convective precipitation in the N Portugal pose a risk for excessive precipitation and thus local flash flooding. Lightning activity of the cells over the land areas should not be high. In the evening and nighttime hours, hunderstorms should receive more thermodynamic instability over marine areas and the lightning activity should increase. A cold front is forecast to pass Iberian Peninsula in the nighttime hours and a marginal lightning activity is possible in the cold sector.
...E Adriatic, E Ionian Sea...
Another shortwave with similar thermodynamic and kinematic conditions is also expected to pass through Balkan Peninsula. However, a higher CAPE along the coastal areas and a support of the orographic lift will result in a more stationary and persistent thunderstorms along the coastal zone. These may result in a higher sums of precipitation and thus a local flash flooding. NWP models indicate the highest threat along W Greece and Albania. It is not ruled out that some convective cells will still remain active after passing the mountain ranges and may produce an isolated severe wind gusts inland.
...E Aegean Sea...
The highest thermodynamic instability and the best overlap with vertical wind shear is predicted in the E Aegean Sea. A boundary layer's moisture content up to 9-10 g/kg and a locally increased lapse rates (~ 7 C/km) will produce in the morning hours a CAPE up to 500-600 J/kg. In contrast to previous areas, a cloud tops should reach mid and high levels, and benefit from DLS that will exceed 30 m/s. Around 03-09 UTC PVU advection will most likely provide a signal for CI. Thunderstorms that will develop in this environment may be evolving into supercells capable of producing severe wind gusts. PW values around 25mm, orographic lift and almost stationary thunderstorms superimposing with stratiform precipitation create also a threat for the excessive precipitation and thus local flash flooding. Thunderstorms should vanish in the late afternoon hours.
... CNTRL France ....
A shortwave trough entering W France in the early morning hours will result in the development of low-topped convection with marginal thermodynamic instability and a significant mid-level air flow. Within the support of a large-scale lift, these may organize into bowing segment capable of producing severe wind gusts. A thunderstorms will most likely develop along cold front an within a small warm sector that will quickly vanish due to an occlusion. Thermodynamic instability and thus risk for severe convective storms should vanish around 18 UTC.
