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Started my analysis with a quick look at the simulated satellite products. Both the IR/WV fields seem to have a relative handle on the large scale features. However – the NSSL WRF appeared to develop vigorous CI around 18Z over central Indiana – which was not evident in the observed satellite data.
In this instance – the NSSL WRF could basically be discounted for at least the next couple hours.
You can see the gaping hole over Kentucky in this nearcast analysis due to extensive cloud cover from earlier convection. Trends are pretty much impossible to detect at this time.
jca
The top two images show the change in forecast IR satellite output over the course of an hour. There is a good amount of enhancement during that time and, as shown in the third image at the bottom of the page, there are some enhanced cloud features with CI values in the 40-60 percent range. This would be a case (where convective initiation is likely within the hour) where having 15 minute WRF simulated IR imagery would be helpful.
-KP
Notices on the NSSL WRF synthetic images that the model erodes low cloud over the high plains much to quickly. This seems to be more noticeable in KS and NB and it does a better job in the high plains of CO. Obviously this kind of error will induce spatial and temporal errors in the wrf forecast.
Kathleen and D Satterfeld
A strong short-wave trough moved through the Central Great Plains, generating severe thunderstorms in a strongly unstable and sheared environment. During the event, we operated in two CWAs: Hastings and North Platte. Forecasters Pelczynski and Anderson operated in Hastings; forecasters Fowle and Satterfield operated in North Platte.
When we started operations, convection had already begun in NC Nebraska, and it began to grow upscale as the sytem moved toward Omaha. Further west, convective initiation held off for some time, before multiple storms fired along the warm front that stretched across central Nebraska. A supercell near Ord, Nebraska became tornadic, and produced multiple tornadoes along its path just south of Omaha.
However, as the cold pool north of the warm front strengthened, it became increasingly clear that a major tornado event would not occur. At the time of this writing, however, it appears that a significant wind event may still occur in eastern Nebraska into southern Iowa / northern Missouri (per the SPC high risk).
-G. Garfield
Week 4 Coordinator
The storm highlighted had a decreasing trend in the prob severe category. It’s trend went from 35% to 11% in less then 20 min while storms just a county to the north had prob severe numbers over 90%. Based on this, we kept the newly issued SVR a county to the north.
jca
Have used the ProbSevere simply to analyze trends in ongoing convection. It is a good “sanity check” simply to make sure all of the ongoing storms are warned. I know the primary purpose was to examine initial development – but the readout provides a quick look at the relevant parameters.
Fowle
For Wednesday, the severe threat shifts eastward with the ongoing MCS in eastern Nebraska. Seasonably-rich moisture will continue to advect northward into the Mississippi and Ohio valleys which – in combination with steep lapse rates – will yield strong instability. However, given our need for a clean pre-convective environment (for our GOES-R products), we are not certain that we will operate in this area (the High Plains may provide a better opportunity). Given the uncertainty regarding the greatest severe threat tomorrow, I will refrain from specifying any specific CWAs for operation. Our shift will begin at 12:30 pm in the Development Lab.
– G. Garfield
Week 4 Coordinator
3 body scatter spike on storm with very high prob severe and MRMS vil 3 grams/cubic M OT Top detection also present. Confidence in severe is very high due to all of the above.
We stopped warning in progress as 3 body spikes disappeared. but we should have gone with it earlier,
DSatterfield
The ThetaE Difference product appeared to provide good guidance on where convection would develop. As has been shown in the past, the gradient in the ThetaE difference product is where most of the action took place.
1930Z:
2030Z:
2130Z:
2230Z:
2330Z:
