14-05-2024 21:46 | Estofex | m.b.t. 16-05-2024 t/m 17-05-2024
Extended Forecast
Valid: Thu 16 May 2024 06:00 to Fri 17 May 2024 06:00 UTC
Issued: Tue 14 May 2024 21:46
Forecaster: TUSCHY
A level 2 was issued for S Germany mainly for excessive rain.
A level 2 was issued for parts of NE Italy but also for parts of Croatia into SW Hungary/NW Serbia mainly for large hail, severe wind gusts, excessive rain and an isolated tornado risk.
A broad level 1 area surrounds the level 2 areas for a similar risk with lower probabilities.
SYNOPSIS
There is not much change to the previous SWODY 1 discussion mainly due to the static nature of the driving synoptic troughs/ridges.
The main change will be a more zonally aligned upper cut-off configuration over W-Europe, which builds into CNTRL Europe. This change in the cut-off's geometry drives the upper jet more towards the Alps and induces also better defined surface votices over N-Italy and S Germany.
This general scenario is well anchored in latest 4-6 NPW runs, which all show the general idea of lowering surface pressure from Bavaria towards N-Italy. Ongoing uncertainties exist, where to place the dominating LL vortices within this broad channel of lowered surface pressure. Latest IFS-ENS however has growing confidence in a confined LL vortex over S-CNTRL Germany with some ongoing zonal spread. The spread increases a bit towards Friday as this vortex lifts N/NW towards CNTRL Germany.
Further S over N-Italy, there is no clear signal of a dominating LL vortex so confidence there remains low right now.
DISCUSSION
... W/S Germany ...
Another round of scattered to widespread CI is anticipated along an extensive LL moisture flux zone, where BL moisture resides around 10 g/kg. Initiating storms once again have a limited time frame for becoming better organized with favorable LL inflow into growing updrafts. Collapsing SR flow aloft however supports growing cold pools betimes, with erraticly spreading small-scale clusters (in general a northward shift is forecast). Isolated hail/ a short tornado event rapidly turns into a more dominant heavy to excessive rain threat, especially with interacting clusters but also along the orography. There is a concern for clusters which move NE over SE Germany to take profit of the enhanced LL SR inflow, which could increase the flash flood risk due to a some training/a slow down of forward motion. Latest EPS data is already concering for numerous excessive and potential flash flood producing rainfall events.
Another area of enhanced flash flood risk exists from far W Germany into Belgium/Luxembourg along the periphery of a transient but closed mid-level vortex, which shifts W/NW. More organized bands of DMC activity could increase the flash flood risk on a regional scale but confidence is not yet high enough for a level 2 upgrade especially as convection to the SE could limit moisture advection into this risk area.
During the evening/overnight hours, the focus turns to far S Germany as the LL vortex is about to evolve. Model guidance is rather persistent in highlighting a confined region over W Bavaria into extreme E Baden-Wuerttemberg, along the W fringe of a Okubo Weiss maximum (centered over CNTRL/E Bavaria) with elongated dilatation axes espcially within its evolving deformation zone.
This kind of configuration combined with expected moist/unstable airmass and strong/deep SR inflow into growing clusters with embedded thunderstorm activity is well known for producing swaths of excessive rainfall. In fact latest model data already indicates 50-100 l/qm within this 12h time-frame. Keeping clustered ENS member of this vortex in mind, confidence is high enough for a flash-flood driven level 2 event (combined with the diurnal risk and admitting a nocturnal decrease of thunderstorm activity in this area).
Beyond 06Z this risk spreads NW along the periphery of the weak LL vortex.
(alleen de voor NL en direct aangrenzende gebieden relevante tekstdelen overgenomen, klik hier voor de volledige forecast, red.)
Onweer/blikseminslag | Verwachtingen/waarschuwingen | Wateroverlast/(zware) neerslag
