Mesoscale Discussion

Mesoscale Discussion
Valid: Mon 15 Aug 2022 06:00 to Mon 15 Aug 2022 08:00 UTC
Issued: Mon 15 Aug 2022 06:06
Forecaster: TUSCHY

A MESOSCALE DISCUSSION was issued to highlight the risk of numerous severe thunderstorms. This MD covers the following time frame: 06Z - 06Z.

Placed along the tip of a mobile subtropical ridge, a strong westerly background flow affects the area of interest. In addition, a progressive but weak LL depression is forecast to cross the area with latest IFS-ENS (MSLP) indicating good clustering as the LL vortex crosses S Corsica/N Sardegna until 00Z.

CAPE/shear space is excellent, which was already sampled by the 00Z sounding of Decimomannu. This capped loaded gun environment is also present further north but with less capping, so CI probabilities increase from S to N (but also increase in the southern part of the MD during the overnight hours).
MUCAPE will be in the 2000-3000 J/kg range along the coasts of W-CNTRL Italy/Corse with up to 4000 J/kg MUCAPE offshore. DLS oscillates aoa 20 m/s with elongated/straight hodographs. Combined with fat mid-level CAPE profiles and modest LL shear (but enhanced LL SR inflow), large to very large/destructive hail is forecast next to severe wind gusts and heavy rain.

Not much background forcing is present, so CI is maximized along the orography, residual outflow boundaries or LL convergence zones, which also set up during the day. This also assists in more discrete CI.
Ongoing convection (06Z) already reveals signatures of intense convection (V-shape signature in satellite data and tight reflectivity gradients in radar data). This activity evolved within a weak WAA regime along a zonally aligned frontal zone.

During the night, ensemble mean of QPF shifts S and so does the severe risk in accord with a passing mid-level low amplitude wave. All kind of severe is forecast including a few extreme events (hail, wind and rain).

Creative Commons License