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 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.

Weak supercells possible tommorow across Serbia

Some marginal CAPE buildup on March 17th (up to 500 J/kg MUCAPE is forecast) in front of the cold front with the surface low somewhere above N-Austria. Potential for rotating storms exists in the central and eastern Serbia where SREH3 gets up to about 200 m2/s2. DLS is about 20 m/s. Main threat will be hail. CIN will be low so the storms will fire up fairly quickly. I usually wouldn't care for this type of setup, but in the early spring (late winter) every semi-severe convective weather is a welcome change.

Top 3 images of 2010

Still suffering from severe supercell deprivation syndrome (SDS) and it's getting worse. Still winter but I guess april isn't too far away. Storm season in Europe usually doesn't start until late april, early may, when the first storms start to fire (we don't have the Gulf ... :( ). We can get first severe storms as late as June, when the storm season in the USA is already in full swing!

So here I'm offering my top 3 photos of 2010.

Supercell and lightning from Medvedje Brdo, Slovenia.

Front passing and morning shelf cloud from Medvedje Brdo, Slovenia.

HP supercell with shelf cloud near Portogruaro, Italy

Honorable mention:

Rotating mesocyclone, large hailer near Trebnje, Slovenia.

June 17th 2010 - High end LVL1 event in Slovenia

Wasn't expecting much from this day but it went really well. My first sight of the supercell was near Trebnje. It took awile to get on the highway ... Missed the first supercell but bagged the next one, crazy driving saved me! :) These storms dropped large hail near Grosuplje and made a lot of damage.

From Trebnje.

Still very unorganized but very active. I was right under all the action. Crazy lift and inflow. A lot of CGs also, was kinda scared to stand outside of the car! Was dropping hail already.

Crazy inflow. Mesocyclone occlusion began here already with rain on the levt. I was moving practially all the time. It was fast.

A few kilometers ahead. Nice wall cloud. RFD really close, wall cloud already a bit in the rain. Not showing the structure very well.

On the road back along Trebnje. RFD on the left, not looking very good.

I still got one more look on the meso once I got ahead of the storm. Really crappy roads here, impossible to track anything here for long period of time.

On the road back at Krško.