Estofex heeft voor onze omgeving code 2 uitgegeven vanwege de kans op supercells met zware regen, hagel, zware windstoten en tornado's.
Estofex schreef:Valid: Tue 07 Aug 2018 06:00 to Wed 08 Aug 2018 06:00 UTC
Issued: Mon 06 Aug 2018 19:54
Forecaster: DAFIS
A level 2 was issued for France, Belgium, the Netherlands and NW Germany mainly for severe wind gusts, large hail and tornadoes.
A level 2 was issued for N Spain mainly for large hail and severe wind gusts.
A broad level 1 area was issued for parts of Spain, France, Switzerland, Austria, Luxembourg, N Italy, Germany, the Netherlands, Belgium, and Denmark mainly for excessive precipitation, large hail, severe wind gusts, and tornadoes.
A level 1 was issued for W Russia mainly for large hail and severe wind gusts.
SYNOPSIS
Several troughs are developing over Europe, especially to the western parts where the most interesting features can be found, destroying the strong ridge that brought new high-temperature records. On Tuesday, two main troughs will create favorable conditions for severe weather, one in W Europe denoted by 2 level-2 areas and a broad level 1, and another one in NE parts of the continent where less moisture and dynamics are forecast.
DISCUSSION
.... France, Belgium, the Netherlands and NW Germany ....
An approaching trough from the Atlantic with strong vorticity advection over a wide area with unstable air masses will lead to severe weather phenomena. First, France will be affected by storms that will be able to cluster in MCSs and supercells producing all kinds of severe weather. At the right exit of the mid-level jet streak the lapse rates may reach 8 K/km creating an overlap of 2-3 kJ/kg CAPE with 20-25 m/s DLS. In the afternoon and night as the storms will propagate NE towards Benelux, increasing low/mid-level shear creates some hundreds of SREH and storms can gain strong rotation, producing severe tornadic supercells. These storms will be able to produce large hail, severe wind gusts and tornadoes.
The level-1 area that surrounds the level-2 areas shows the locations of the storms where they may become severe. Locally large hail, severe wind gusts, excessive precipitation from slowly moving storms and landspouts / tornadoes are well possible especially during the late afternoon - night. Thunderstorm activity will continue overnight till the morning of Wednesday but with a limited threat for severe phenomena.
Zie ook
https://www.noodweer.be/hitte-op-dinsdag-gevolgd-door-fel-onweer/ "Hitte op dinsdag gevolgd door fel onweer?".
In de "Guidance modelbeoordeling" van het KNMI op
https://www.knmi.nl/nederland-nu/weer/waarschuwingen-en-verwachtingen/extra/guidance-modelbeoordeling lees ik het volgende:
KNMI schreef:Bewolking:
Morgenavond van het zuiden en zuidwesten uit kans op een CB's met basis rond 9000 vt, toppen rond FL370.
Neerslag:
Tot en met in ieder geval dinsdagmiddag droog. Dinsdagavond van het zuiden en zuidwesten uit kans op onweersbuien, SBCape 1500-2000 J/Kg reikt tot over het zuiden. In combinatie met een effectieve schering van 20-30 kn kunnen er goed georganiseerde buien ontstaan. Hagel is mogelijk. De modellen laten deze toch geleidelijk minder actief worden. INDECS komt deze run met grotere onweerskansen (meer dan 1 ontlading), 40-50%. Als het tot onweer komt dan is de kans dinsdagavond en in de nacht naar woensdag vrij groot dat er veel ontladingen zijn. Kans op meer dan 50/5 min is dan circa 60%. PW loopt in Harmonie lokaal op naar 40-50 mm. De 700 hPa-wind neemt echter snel toe naar meer dan 30 kn, waardoor de buien snel doorlopen.
