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Mesoscale Discussion Valid: Tue 09 Jul 2024 10:00 to Tue 09 Jul 2024 13:00 UTC

09-07-2024 09:43 | Estofex | m.b.t. 09-07-2024

Mesoscale Discussion
Valid: Tue 09 Jul 2024 10:00 to Tue 09 Jul 2024 13:00 UTC
Issued: Tue 09 Jul 2024 09:43
Forecaster: TUSCHY

This Mesoscale Discussion was issued for updating reasons. The validity of this MD does not match the anticipated severe risk, which probably starts around 12Z to 13Z and lasts into the overnight hours.

Latest surface data places a weak LL pressure channel from W-CNTRL into NE France with latest data still pointing to a gradually developing and more dominant vortex over NE France, before moving into Belgium/the Netherlands. Latest surface observations already show a vortex next to Paris (10Z). IFS-ENS remains a tad more W with the vortex compared to ICON, but overall NWP guidance remains rather consistent. Ongoing vortex spread still causes a rather broad MD area for now.

Enhanced LL convergence along the evolving low pressure area increases LL moisture depth with dewpoints of mid/upper tens causing MUCAPE in the 800-1300 J/kg range around peak heating. ID2 comes in less agressive but this model has highest warm sector T2m temperatures compared to others with attendant mixing resulting in somewhat lower peak values. Amount of weakly capped CAPE is enough for scattered/intense CI beyond noon. In fact, ongoing convection NE of Paris has a good chance to root into the BL with 25/16C ahead and we might see this growing into a dominant bow.

Most models agree in bringing a 40-50 kt 700 hPa speed maximum into the growing convection from the SW, which assists in 0-3 km shear values along the front of 15-25 m/s and enhancing deep cold pools with forecast temperature gradients of 10K and more. This activity also takes profit of a deeply/well mixed air mass they move into.

ID2-EPS constantly highlights parts of the MD area with probabilities in the 30-40 % range for gusts in excess of 105 km/h and up to 25% for 120 km/h gusts with most models indicating longer-lived bow echo activity within the MD area.

The risk lowers into W-Germany as CIN increases beyond sunset.

Beside the dominant wind risk, isolated large hail and heavy rain will be another issue. A tornado risk is very low-end due to a high LCL environment. With the forecast intense SRH setup, we still can't rule out an isolated event, driven on the mesoscale (e.g. along book-end vortices or due to lowered LCLs by preceeding convection).

Hagel(-schade) | Onweer/blikseminslag | Verwachtingen/waarschuwingen | Wateroverlast/(zware) neerslag | Wind/storm (-schade)