Storm Forecast
Valid: Mon 17 Aug 2015 12:00 to Tue 18 Aug 2015 06:00 UTC
Issued: Mon 17 Aug 2015 12:32
Forecaster: VAN DER VELDE
A level 2 was issued for N Bulgaria and E Romania mainly for excessive convective precipitation and large hail.
A level 1 was issued for parts of Central Europe mainly for isolated excessive convective precipitation and isolated tornadoes.
A level 1 and 2 were issued for the Balearic Sea area mainly for excessive convective precipitation and large hail.
A level 1 was issued for parts of Ligurian and Adriatic Sea for tornadoes.
SYNOPSIS
A mid level low is present over northern France, its influence reaching over Spain, Italy, Balkan and Central Europe, where low presure cores are found at the surface. High pressure is over Scandinavia. A frontal zone with warm and very humid air is stationary over northern Germany between flows of cooler air from France and Poland. The largest instability is present over the Balearic Sea and over the eastern Balkan.
DISCUSSION
...Romania and Bulgaria, Hungary...
Moderate deep layer shear (10-15 m/s 0-6 km) with local SREH over 200 mē/sē allows for some supercells among multicell clusters with potential for large to very large hail.The storms form in a strong 1000-2000 J/kg MLCAPE environment lifted by a PV anomaly moving east. Storms will likely train over regions, with excessive rain sums as result. In Hungary, the PV anomaly coming northward should trigger a number of storms, while convective cell motion will be so slow that several storms may cause local excessive precipitation, and spout-type tornadoes may also form.
...E Spain and Balearic Islands...
Over 20 m/s 0-6 km shear combined with 1500-2500 J/kg MLCAPE creates potential for supercells although lower level shear is weak to moderate. Multi/supercell storms will feature large hail and likely some waterspout-type tornadoes. Low-level moisture advection They may produce excessive precipitation especially when a large cluster stays over coastlines, particularly in the night (early morning) when a sharp trough arrives with large-scale lift.
...Czech Republic to North Sea...
Very humid air will destabilize to only a few hundred J/kg CAPE. Lifting should be only by convergence at low levels, while no destabilizing support is present in higher levels. Storms will move NW-ward along the front, with potential of local training enhancing the rain sums. The chance of tornadoes is present as very low LCL combines with strongly veering hodographs in the lower levels with some overlap with CAPE. Some WRF models predicted SREH values over 400 mē/sē. On the other hand, deeper layer shear is only weak to moderate so not that supportive of supercells but this may enhance precipitation efficiency. The weak CAPE however makes the potential for severe weather quite fragile.
...parts of Ligurian and Adriatic Sea..
Waterspouts are possible as airmass destabilizes later in the day (night) in convergence zones near the Italian coasts. Near the core of the low slow storm propagatio, low shear and high ambient vertical vorticity aid spin up.
