Serious potential for strong (tornadic) supercells on June 18th in FVG, Italy

Estofex gave LVL2 for today in N-Italy and the setup really is very good. I won't really into details because time is not on my side. Just a quick writeup. 50 kt 0-6 km shear combined with good SFC winds with nice veering and moderate CAPE values suggests serious potential. The best potential is again in the FVG region where winds are the best. The cap is not small and there is no serious 10m convergence until 18Z so we will see if it can break it anyway. PWAT values are ridiculousy high, in the 42mm range, so everything points to (potentially tornadic) HP supercells. Good luck to everyone who will chase today. I won't be chasing because of college work. :(

Follow up on the June 6th setup

For initial analysis view the previous post. Potential for the June 7th has vanished due to weak 0-6km shear. June 6th looks solid, the 500mb jet is going to be stronger than expected at first.

We are dealing with 35-45 kt 500mb jet through northern Croatia, Slovenia and NE-Italy, around 30kt @ 700mb, 20kt @ 850mb and around 10kt @ 925mb and 10m. Limiting factor is the unidirectional shear, which limits helicity, so supercells are possible, but not very likely. Storms will tend to get linear. Focus will be on the southern flanks of the lines for possible tail-end charlies. CAPE will range from 500 to 2000 J/kg according to WRF and GFS, locally maybe even more. Areas with high CAPE are forecast in CNTR-Italy, E-Slovenia and N-Croatia. No significant convergence lines other than above the Dinaric mountain range and the Alps are forecast, but the CINH will be rather small and with some daytime heating we should have no problem seeing breaking the cap. Similar conditions exist for E-Austria and W-Hungary.

Severe weather potential for N-Italy, June 6th/7th

Weak trough passes through central Europe, showing some signs of storm potential. As I look at it now, the limiting factor will be the upper level flow, only at 30kts @ 500mb which is seriously borderline. Low level winds on the other hands are quite good, with good speeds and direction make up for a nice veering profile. Higher CAPE is forecast on June 7th with more marginal conditions on June 6th. The cap will be somewhat moderate, but with lack of surface convergence, initiation is questionable. WRF is even drawing a 10m wind divergence in FVG region. Stay tuned for updates and detailed analysis in the next few days.

Severe storms potential on Friday in FVG, Italy

Severe weather is expected on Friday afternoon in Italy, Austria, Slovenia and Hungary as the trough advances eastward. The trough will provide a 15-20 m/s 500mb jet and adequate lift on the front which comes in the late afternoon in N-Italy, N-Slovenia and W-Hungary. Models still do not agree with each other on how much CAPE will be available although they are starting to converge. GFS forecasts >1000 J/kg in NE-Slovenia, >1500 J/kg in N-Croatia and only a couple of hundred in central Italy with marginal CAPE in Friuli-Venezia region. ECMWF and GFS are drawing more CAPE in FVG region and less in NE-Slovenia.
The wind profile is great in the FVG region and a lot worse elsewhere. Medium SRH3 and nice veering suggest for potentially tornadic supercells. That will be basically the only interesting region. Other locations have more or less uni-directional shear so linear storms will probably be the primary mode. Still, large hail is definitely a danger, including severe wind gusts, but to a lesser extent, given the high moisture and PWAT values. High PWAT values also suggest HP supercells in the FVG region. With some low-level shear, tornado is not ruled out.

My biggest concern is the capped atmosphere in the FVG region. Elsewhere the cap will be broken rather easily. I remain somewhat sceptical for Italy. There is a strong convergence west of Venezia and Bologna, but the lack of serious lift in FVG region, the initiation prior to the front is questionable. Once the front comes, there will be no problem with initiation, but this will probably be rather late. I think the CIN will be in the 30-60J range and with the lack of serious convergence zones the initiation can be late.

The severe weather potential in NE-Slovenia and elsewhere along the front will be limited due to lack of low-level shear and these locations are probably not the best chasing targets.

Small CAPE/large shear setups

In the spring we are dealing with a lot of situations where there is weak or marginal cape and large deep layer and low level shear. These situations can sometimes produce strong tornadic supercells providing large storm relative helicity values. I've stumbled across this interesting point made by Jon Davies on his blog. You can read it HERE.

Similar conditions are currently in southern Poland, Slovakia and further to the south-east. No reports yet. Strong SREH3 is forecast tommorow in the same area with marginal CAPE. Tornadoes are possible.