May 27, 2012

May 27: Back to North-central KS

Panorama shot just north of Ellis of departing Hays supercell, shown below, road goes due north. You can see the southern end of the Nebraska line of storms sort of over the road in the distance
What We Saw

We saw multiple storms firing off the dry line/triple point area alluded to below, from around 4PM on, southwest of Hays KS. 

Shot of RFD notch in Hays supercell, illustrating high base.
This shot is looking due west (road goes west)

Shot of same as (2) except showing whole updraft tower.
There was definitely lots of precipitation on the forward flanks. There was also lots of precipitation wrapping around the updraft areas with the weak an broad mesocyclones that had formed.  But the LCLs were so high that the moist adiabatic ascent did not occur in the area of the really wonderful clockwise loops in the hodographs. The key here would be the 0-3 km CAPE, which in May 27ths case was really negligible.
There were some "CAPE-robbers" in the soundings related to the negatively tilted trough that moved northeastward. A negatively trough that is "minoring out" as it moves northeastward is really experiencing height rises relative to a coordinate system fixed with respect to the trough. The height rises hypsometrically are related to temperature rises. 
Fibrous anvil for storm south of Hays near sunset.  
So most of the updrafts we saw had mushy tops. The best look were the storms that we could see in Nebraska. I think that updrafts were weaker for our storms, even if the CAPE area was deep. Not quite "tall skinny" CAPE....but definitely pretty anemic CAPE. 

What was clear was that the atmosphere wanted to produce lots of storms, and there were several surges of initiation northeast of Dodge City.   Storm after storm formed there, but each had those high bases, and each had kind of mushy tops and fibrous anvils.

Departing Hays supercell.  View looking northeast, shot a few miles north of Ellis.
I have posted here some other pictures showing the state of the sky near Hays just before initiation. (panorama).  I've also posted a panorama of the first set of storms after they formed.  And finally there is a picture of a wonderful fibrous anvil with mammatus on it and all sorts of wave like perturbations in the cloud material.

Cumulus field southwest of Hays, just before thunderstorms developed.
First thunderstorms, south of Hays, around 4PM.  View looking southwest.

Meteorological Blather

I am in North Platte, Nebraska this morning with Scott Landolt.

A negatively tilted short wave trough in the middle and upper troposphere will be incoming today. I often don't like them in the they often are associated with difficult to diagnose temperature advection patterns in the middle and upper troposphere...meaning weak areas of warm advection producing "CAPE-robbers" in the soundings.

However, models are generating a weak low over southwest KS, which should swing the surface winds around to southeasterly over the area about 50 miles north and south of a line from Hill City to Concordia, KS.  The WRF-NAM has interesting looking soundings and hodographs over north-central KS into south-central Nebraska tomorrow afternoon. Further east, the soundings look too capped.   And even in the area of interest, the recurrent problem of inadequate dew points seems to be indicated, suggesting that storms will be high-based.

However, the general setup is good from north central KS to extreme south central NE.  We'll refine the target later this morning.