CIMSS NearCast 900-700mb Precipitable Water Maximum Values in Arkansas – Similar to ThetaE Diff Post

The CIMSS NearCast 900-700mb Precipitable Water product depicted a maximum of values 7 to 9 mm at 19 UTC on May 15 in southwest Arkansas (top image).  The next two images of this variable depicted at 22 UTC and 24 UTC have this maximum area moving east southeast into southeast Arkansas around 22 UTC then northwest Mississippi by 24 UTC.  I wonder if storm development will follow this maximum area for the next few hours.  If so, the NearCast forecast tool would be especially useful in near term forecasting (1-6 hr) and can give forecasters a heads up where and when convection occurs.

This post is very similar to the ThetaE difference post.

Michael Scotten

CIMSS NearCast Vertical ThetaE Minima May Have Great Handle on Convection in Arkansas

The CIMSS NearCast Vertical Theta-e Difference Mid-Low product depicted a minimum area of values -2 to -3 K at 19 UTC on May 15 in southwest Arkansas (top image).  The next two images of this variable depicted at 22 UTC and 24 UTC has this minimum area moving east southeast into southeast Arkansas around 22 UTC then northwest Mississippi by 24 UTC.  I wonder if storm development will follow this minima area for the next few hours.  If so, the NearCast forecast tool would be especially useful in near term forecasting (1-6 hr) and can give forecasters a heads up where and when convection occurs.

Simulated Satellite Imagery Analysis – Thursday 1815Z

Just a quick look at how the simulated satellite imagery is doing early this afternoon.  It appears to be doing pretty well!  It may be just slightly overdone with convection across Oklahoma, but it has a pretty good handle on the larger-scale features.  It definitely gives me some confidence in this model going forward through the day.

Simulated Satellite Imagery versus observed satellite imagery – 1815Z

EWP Status for 15 May 2014: 12:30-8:30 pm Shift

As the Mississippi Valley trough continues to shift eastward, so will the severe weather activity. The most active area for today appears to be from South Carolina into Virginia. One group will be focused in the Sterling, Virginia CWA to hopefully take advantage of the DC LMA. The other group will operate in the Shreveport CWA, where a marginal threat for hail is present. In contrast to the activity on the east coast, this development will be from the clear sky, where most of the GOES-R products have their greatest utility. Additionally, this group will be able to utilize the OUN WRF model.

SPC's hail outlook highlights the threat in the ARKLATEX region.

SPC's tornado outlook highlights that threat along the east coast.



- Bill Line, SPC/HWT Satellite Liaison and Week 2 EWP coordinator

Daily Summary: Week 2, Day 3

Today, we began operations in the Wilmington, OH and Nashville, TN CWA’s. Once again, convection along the cold front was ongoing from the previous evening. The folks in Wilmington were able to utilize many of the products as there was some clearing earlier in the period. The participants in Nashville were able to view the PGLM Total Lightning data from the Huntsville LMA, though activity was not that great, and many of the other products were not usable given the extensive cloud cover. As the lightning activity subsided, the Nashville crew moved to the Pittsburgh LMA, where new storms were beginning to initiate, and the forecasters could utilize more of the demonstrations products. The group in Wilmington would later move to the Charleston, WV CWA as convection spread eastward, before ending up in the Cleveland CWA.

Tomorrow, we will start activities at 12:30 in the Dev Lab for the daily debrief before moving to the HWT for the EFP briefing. The day looks to be similar to today, as the cold front continues to shift towards the coast. One group will likely focus activities in the DC LMA area, while the other group may work in southeast OK as that area may see some convective development from the clear sky.

Feedback:

Simulated Satellite Imagery

• I looked at it early in the day, and it was quite accurate. THis gave me confidence in the forecast throughout the rest of the day
• I was impressed with how it simulated features in the IR and WV. It looked really good.

NearCast Model

• There was a lot of early cloud cover which limited its use. But it did have moisture and nice stabilit yriding up along the cold front, as I would have expected.

GOES-R CI

• At night it became useless. I do not see myself using it then, but I rally like it during the day
• It was too cloudy much of the day for it to be useful
• There were many low probabilities showing up within and along the edge of a broad stratus deck where convection was certainly not going to develop.

Prob Severe

• In Huntsville, it didn't show very high probs for the low-topped convection (QLCS, ~25K ft.). Mainly wind damage reports with this. I still think that it is best used in hail situations
• there was a supercell in Ohio that it only gave 5-10% probs. This was very low-topped.

Tracking Tool

• It was cool to use with the supercell to show reflectivity trends, then a slow decrease in magnitude
• I think these trends would be helpful
• I also looked at SRM; it could be helpful to see trends in that, maybe giving you confidence in tornadic situations
• I would like to manually input the melting level and track reflectivity with that displayed

- Bill Line, GOES-R SPC/HWT Satellite Liaison and Week 2 EWP Coordinator

CI Tool – Use of CI tool at night

CI Tool at Night

After diagnosing the CI tool once it switches to the coarser resolution using IR, I just don’t think it’s usable.  It’s way too noisy and very inconsistent, almost unusable in my opinion.  I love this tool during the day, but I honestly just don’t think it’s worth the data crunching to run at night.

- Deitsch

Overshooting Top Detection Continues to Underestimate Overshooting Tops

The GOES-R Overshooting Top Detection (OTD) product continues to underestimate the number of overshooting tops.   In the top image at 2315 UTC, there are several cold cloud tops around -60C with several severe storms in Ohio, western Pennsylvania, and West Virginia.  The OTD product only detected one overshooting top over Ohio at this time.

The OTD product seems to be underestimating the number of overshooting tops today on May 14.

Michael Scotten

EDIT: 

I made it clear to the forecasters that even though these storms had cold tops, that does not mean there is an overshooting top. I had them sample the area and it was clear that the OT algorithm was correct in not detecting OT's, as they were just uniformly cold tops, not overshooting the trop. When training forecasters to use this type of product, it is important to make these types of aspects of the products clear.

ProbSevere got a jump on a SVR in PBZ area

The ProbSevere model was useful in spotting a convective cell that popped up in the Pittsburgh area late in the afternoon. The rapid scan GOES imagery, overlaid with ProbSevere, shows a few cells worth keeping an eye on. The northernmost shapefile in pink was in an area that I otherwise would have ignored, because I didn’t see any visual cues in the visible imagery that indicated convection in the immediate area of the pink outline.

At the time when I was looking at this cell, I also had the Theta-e differential overlaid, to see if that was pointing out any unique features. I dialed down the opacity of the color table so it wouldn’t interfere too strongly with the high-res sat data. For the picture below, I pushed the opacity back up to clearly show the colors. As you  can see, there is a relative maximum over the ProbSevere shapefile of about -9.0K, but without the ProbSevere shapefile, this area wouldn’t have caught my attention, since there are other areas with that same intensity, and the values weren’t too impressive, either. That said, the -9K blob on the right was in an area with developing Cu, whereas the blob on the left didn’t have Cu development yet. So I guess in retrospect, I could have taken notice to the area with relatively high Theta-e difference in conjunction with the developing clouds. I do feel like the ProbSevere gave a jump on any visual confirmation I might have made on changing cloud structure, because like I said before, the clouds did not look that impressive to me.



The vertical PW difference wasn’t showing any impressive values, either, but something that’s worth noting is the gradient that formed right in the warned area. As we know, gradients are conducive to volatility, and the storm’s path actually tracked right along this gradient, moving due north. The image below is valid at 22:00Z. A warning was issued in the circled area at 22:27Z.



This cell had been warned earlier in the afternoon, and redeveloped. The ProbSevere model might prove to be very useful for tracking storm cells, not just before they become severe. It could also be useful after a storm loses its severe characteristics by tracking its redevelopment potential.This could be very useful for a forecaster to help them sift through the clutter, especially in events with lots of pop-up cells and in linear MCS events.

ProbSevere Model verified with 3BSS

The following three images follow a cell northward across north-central WV using the ProbSevere Model overlaid on KPIT 0.5 degree radar reflectivity. The first image below is from 2224z where the sampling box shows the ProbSevere model with a 6% probability of a severe storm. The Multi-Radar Multi-Sensor MESH size was 0.17 inch within an environment of 2135 J/kg MUCAPE and 21.2kts EBShear. There was strong vertical cloud growth rate and a moderate glaciation rate calculated from satellite imagery.

14 minutes later at 22:38z the ProbSevere Model severe probs jumped to 95% with the only change in the predictors being an increase in MRMS MESH to 1.74inch.



9 minutes later at 2247z a three-body scatter signature (between the annotated arrows) shows up on the KPIT radar to the south of the storm core. At 2254z golf ball sized hail was reported in Salem, WV.



Shawn Smith

GOES-R Convection Initiation Nails Developing Storms in Wonderful West Virginia

The GOES-R Convection Initiation product handled developing convection in West Virginia with 15-45 minutes of lead time on May 14.  The top image displayed visible imagery with CI values along a few bands of enhanced cumulus with values 51-84% highlighted in the green, yellow, and orange areas at 2015 UTC in the middle part of West Virginia.  The second image with RLX reflectivity depicted very little to no convection at 2015 UTC.  The last image depicted RLX reflectivity at 21 UTC with isolated to scattered storm development where CI values were 51-84% about 45 minutes earlier.

This product continues to perform very well.  CI values greater than 50% have been shown to indicate developing convection with high confidence.

Michael Scotten