April 9-11 Storm for Central portion of US

Fellow bloggers,

Keep this short but any of you following run to run consistency of next weeks storm?

Does it get much better or worse than the Midwest in April? What a forecast challenge.

Few days ago it was a possible thunderstorms with 60s for madison...

now today's 12 ECMWF and GFS put Madison in line for snow...

Nothing like a Mid-Summer Case Study

Link to Severe Storms in Eastern Minnesota...aka...A pitch to get people to buy GR Analyst
http://www.crh.noaa.gov/images/mpx/NewsStory_June14.pdf

Nebraska: 5.5.2012

Hey Chasers, I will be heading out to Nebraska for a chase tomorrow. A developing triple point area looks to be the site of supercells tomorrow afternoon. The initial target is Hyannis, NE and I will adjust north/south accordingly depending on how the Cu field looks in the late morning. I'm expecting a few supercells even as early as 19-20Z from about Hyannis, NE to Martin, SD. I see decent tornado potential with cells moving slowly and having good directional shear south of the triple point. Some more speed shear would be ideal, but I'm not complaining (yet). I will be sure to post pictures and footage if we get anything good. Dima the Dryline

Recap of 4/12 & 4/14

Today was one heck of a day in Kansas. In retrospect, we can all probably say we should have gone there, but it's not clear why Nebraska was void of any significant tornadoes.

Anyways, I have a few quick videos from Thursday and today.

Thursday 4-12-2012:

I went up to Sterling, CO then east to Imperial and down towards McCook, NE. First, here's a video of hail east of Sterling. This was a nuisance because it created some thick hail fog and the temperature crashed from the mid 60's to the upper 40's in basically 10 minutes.



After this, I wandered along the warm front eastward, where the following picture recaps the common sight: towers getting choked and undercut by the cold air to the north that seemed to slosh north/south like a tide. I've heard people refer to these kind of towers as "turkey towers". The darker clouds are shallow stratus.

Finally, with the help of ours truly Squall Line, I was in position to take this footage a few miles north of Trenton, NE around 6pm. The video is bad quality (time to invest in a good camera), but at 0:45 seconds in, I think there's a funnel in the middle of the screen. This happened to coincide with the location and timing of the tornado report on the SPC reports.



Saturday 4-14-2012:

I was lazy today and paid the price. My goal was to head out to near Ogallala, NE as the 500-mb cold front was moving over the triple point. I like those situations as they always produce funnels/nados even though the cells are usually ugly looking on radar. I left too late though and was playing catch-up the whole time. I did manage to snag this cool video of a cell that later produced a few funnels near North Platte. The precip shaft in the middle is sweet.

Why Nebraska?

All of these ingredients will conveniently find themselves in a single location tomorrow afternoon...

• Nose of upper level jet
• strong diffluence 
• strong curvature from downstream ridge amplification over the course of the last 18 hours
• More than sufficient instability
• synoptic flow will keep morning warm frontal convection cirrus and debris from hampering afternoon destabilization
• Strong cyclogenesis
• bulging dryline and cold front
• pressure falls in region (Dima I know you like that parameter)
• Excellent vertical speed shear (ie bulk shear)
• lowest 1.5 km speed shear of 30 knots
• SSE wind at surface and SW at 850 (ie helicity)
• further enhanced shear from LLJ hour or two before sunset when storms are still coupled with BL

And this...

Hail but Not Much Else: Added thoughts

The image above is the sfc analysis at 2243Z yesterday as those three monster storms had just formed off of the dryline in northwest Kansas. the orange line is the dryline and the red line is the location of the warm front. The blue arrows depict the storm motion at the time. I think the biggest reason that there were no tornadoes ties in directly with what Dima (Dryline) was saying. The warm sector with temps above 70F and where the highest cape values (>2000 J/kg) was very modest in size. Each one of those supercells that formed off the dryline grew in a very favorable area to become tornadic; however based on storm motion they were not able to remain in the warm sector for very long before riding over the top of the retreating warm front and into much more stable boundary layer (Temps in the 50s/60s) even despite the strongly backed winds. Cape values to the north and east of the warm front where near 0 as Dima was saying and each one of those cells basically crapped out into a hail producer as they moved northeast into southwest Nebraska. The cells farther to the north seemed to be more dynamically driven and grew upscale as the shortwave was moving through (moving into more unidirectional shear) but again like the cells Dima was on to the south had no real chance at producing tornadoes.

It's tough to see such a favorable setup fail so hard. Storm motions would have had to have been much slower and more to the east, or if the cap could have broken earlier along the dryline while it was farther west across eastern Colorado. Anyways, I would say that was a pretty successful chase yesterday Dima and just a taste of whats to come for you the rest of this Spring into the upslope summer. Post some pictures when you get a chance.

Dan aka Squall Line

Hail, but not much else

After many promising cells (I counted chasing 4 or 5 65-dbz storms), I got hailed on 7 times, video to come later. Tornado wise, today was a letdown. I did not see well-developed wall clouds. All the rotation was on the scale of the whole thunderstorm with lots of unorganized turbulence producing funnels everywhere. Like I told Dan, who helped me catch the cell near Trenton, NE around 5-6pm, the report of a tornado looks to be an error because there were very low-lying clouds associated with the warm front the kept moving north/south after interaction with the passing cells.

Why the lack of tornadoes today? I would say instability. I measured low 60's over low 50's even south of the warm front, which was probably amounting to a few 100 worth of CAPE.

Still debating whether to head out Saturday. Looks like the show will be mostly after sunset. Anyone agree or disagree?