Something to Watch Charley

Have a new CI ping, 70-80% in Fall River county.

Looking at the Nearcast model, have a little peak that bends down to that point in the county.  Will have to watch to see if we get new development there.  It is a little drier down there, so wonder if a storm that forms here may have better mix down of winds.

UPDATE:  That cell did not develop, however we have another high CI signal later, here:

Pennington Co., SD Verification

After warning the cell multiple times, we finally started to get reports to verify our thinking.

We had 1″ hail reports at 3:25p and 4:15p and a 1.25″ report at 3:28p, all in Pennington Co.

Our first warning was issued at 3:02p based on ProbSevere, a few lightning jumps and DVIL with little help from Convective Outlook (only general risk).

-BT and Charley

NASA TV interviews given

A few of us did interviews with NASA TV concerning what we were doing at the HWT, the use of GOES-R products, how it will change things, and how forecasters will train and ultimately use them in forecast and warning operations.  They may show up on social media and NASA TV at some point in the future.  I compared GOES-R to going to HD or UltraHD (4K) in TVs.  MrSnow

CI Increasing – Developing Convection?

CI percentages are increasing across western MN late this afternoon. MLCAPE values in this area ahead of a cold front have increased into the 1000 to 1500 J/kg range… with deep layer shear in the 40 to 50 kt range. This may be the first signs of a possible line of strong to severe storms developing over the course of the next couple of hours.

-Wacha

CI and Overshooting Top observations

Living vicariously through Minneapolis and Aberdeen…

The 2130Z Visible with the overshooting top and CI overlaid shows a few interesting things. There is currently an overshooting top with the strong/severe convection over Grant County, SD. Current IR Imagery shows a core of -58C surrounded by a broad downwind anvil of approximately -53C. There is a tighter gradient of cloud temps on the upwind side of the anvil, with temperatures on the edge dropping quickly into the upper -40s C.

Also, the CI values began to highlight an area east of the ongoing strong convection with two scans showing greater than 90% chance of convective initiation. On the corresponding 2130Z radar image out of MPX, only a weak shower is shown.

Fast forward to the

Flash Forward to 2207Z, there has been no further development with the cell that showed promise in the CI in Pope County, MN

-Shasta

ENI Lightning products/CIMSS Prob Sev in BOS

Lighting products even thunderstorm alert not picking up on cell that had a report of wind damage.

One minute lightning showing strikes but not sufficient enough for products on the first frame

CIMSS product showing low prob of severe.

Noting that with the short line segments, somewhat marginal conditions for severe weather, with wind being the highest threat, that the lightning products and the CIMSS prob severe product has not helped us pick out the storms with highest probability of producing at least close to severe wind. We were watching closely the cell that we eventually warned on over Worcester Co. and decided to issue when we received a report of trees/limbs down by law enforcement.

CIMSS Prob Severe confirming our radar interrogation

Just noting current frame and prob severe has been confirming what we have seen on radar some short bowing line segments and we agree the threat seems to be wind…but from what we have been seeing on velocity products they have not been meeting severe criteria. Although we did just receive a report of some trees down in Worcester Co…maybe our first warning.

Cell in SD

Despite rapid initial cloud growth, it took a little time for the cell in Custer Co. to mature. Before any type of warning was being considered, a 90% ProbSevere showed up before lowering to ~30%. While working on another monitor, the ProbSevere jumped back to ~90% which grabbed our attention and ended up leading to a warning being issued. We issued an SPS about 7 minutes prior.

Working in this environment of cells vs lines, it’s easy to see ProbSevere is much more accurate.

UDX NUCAPS sounding

 Initial NUCAPS (below) had a low SBCAPE, based on dry conditions.  Temperature looked good on original sounding, but when I moistened the environment up (image above), got to the 4500-5000 CAPE SPS meso was showing earlier.  Large spread of dewpoints over the area, likely b/c of topography?  Perhaps the RUC smoothes over those dewpoint changes and that’s the reason SPC meso had the large CAPE.

High Initial ProbSevere

First probsevere came in with a 71% probability for severe.  Show a very quick growth rate, expected from high low and mid level lapse rates.