Storm Forecast
Valid: Tue 24 Jul 2012 06:00 to Wed 25 Jul 2012 06:00 UTC
Issued: Mon 23 Jul 2012 21:58
Forecaster: KOROSEC
A level 2 was issued for parts of southern Italy mainly for excessive convective rainfall and lesser extent for large hail, tornadoes or strong winds.
A level 2 was issued for central Adriatic coast mainly for excessive convective rainfall.
A level 1 was issued for surrounding areas of level 2 across Adriatic sea as well as Tyrhennian sea mainly for excessive convective rain, marginally large hail and a few waterspouts.
A level 1 was issued for WNW Balkans mainly for large hail and isolated strong winds.
SYNOPSIS
An upper low slowly diminishing over central Mediterranean while moving NE-wards across Italy and Adriatic sea. A LL depression over Tyrhennian sea gradually weakens but remains rather stationary during the day there and makes slow progress into southern Adriatic sea towards the night to Wednesday.
DISCUSSION
... parts of southern Italy, central Adriatic coast...
A level 2 has been issued for areas exposed to additional excessive convective rainfall threat on the front flank of the cyclone over southern Italy. With strong LL advection of warm/humid airmass onshore towards southern Apennines, intense storms with flash floods threat are likely. Moderate instability overlaps with still around 10-15 m/s of deep layer shear and some SREH which should support storm organization into multicells and a few supercells. The main threat will indeed be excessive rainfalls, while locally some large hail will be possible as well. A tornado/waterspout threat cannot be excluded either, especially given the enhanced LL shear/SREH along the numerous outflow boundaries interacting/firing new deep convection.
Later in the forecast period, the excessive convective rainfalls threat shifts towards the eastern Adriatic coastal areas as winds turn more into southerlies and strong orographic lifting occurs there. Expect locally some training cells effect to produce intense rainfalls and enhance flash floods threat. Still some shear and quite high instability should support organized storms, those could spark a brief waterspout(s) too.
Surrounding these areas, over Tyrrhenian sea and Adriatic sea, a threat for more isolated nature of events will exist given the still moderate instability but rather low shear. Given the lack of stronger wind field in the wake of the surface low, a couple of waterspouts could occur especially over warm SSTs of Tyrhennian sea.
... WNW Balkans ...
With a gradual NE-ward progress of upper low, cold mid levels will overspread the Balkans on Tuesday. Healthy moisture recovery will be on going towards NW Balkans with quite strong WAA from the south. As a result, moderate instability will become available during the afternoon/evening hours. With still well defined mid level jet rounding the upper low, at least some deep layer shear will remain in place for storm organization. Expect mostly multicellular storm nature and locally a supercell or two as well. These storms could pose threat for some large hail and isolated stronger winds. A level 1 was issued to cover this threat.
... central Iberian peninsula ...
A weak geopotential falls are expected over SW Europe and beneath the improving EML the returning moisture inland could support a few isolated storms over central Iberia. Too conditions threat limits the high lightning probs, as well as severity given the lack of deep layer shear.
