Week 2 Summary

This week, the EWP had forecasters from the Louisville, Buffalo, and  Norman WFO’s, as well as a broadcast meteorologist from WUSA (DC CBS affiliate) participate in the Big Spring Experiment. Operations on Monday began in the Davenport and St. Louis CWA’s. Throughout the week, operations slowly shifted eastward as we evaluated the products with severe weather development along an eastbound cold front. These operations included the Detroit, Cleveland, Wilmington, Charleston WV, Pittsburgh, and Sterling CWA’s. One group on Thursday operated in the Shreveport CWA, where marginal severe weather occurred as an upper level disturbance moved through a region characterized by weak low-level moisture but steep lapse rates and only marginal instability. This unique environment posed some interesting forecast challenges, so it was neat to see how the various satellite products and OUN WRF performed.

Participants were able to use all of the demonstration products this week, which included  GOES-R and lightning products, LAPS fields, and the OUN WRF model finally on Thursday. There were many good blog posts written throughout the week highlighting the use of all of these products in various situations across various regions of the US. Below is some end-of-the-week feedback on each product from this weeks participants:

Simulated Satellite Imagery:

• This gave me a heads up on where clouds would move. There isn’t great guidence for sky grids, so I would look at this to see where stratus is moving, etc. if it was verifying well
• I think it is especially effective on the large scale because it picks up on large scale features well.

NearCast System:

• I liked and used it because it is observed thermodynamic data, of which there is very little
• This added value to my forecast process. For example, in West Virginia no boundary was evident at the surface, but there was a boundary in NearCast, and that is where convection fired. That sold me.
• I do not like to rely on NWP data, so this was nice.
• I really liked seeing the gradients, most of the storms developed in theta-e difference minima or moisture maxima or along gradients.
• There were a few cases where you saw decreasing moisture moving in, which was not picked up in the models, and it did have a big effect on storm development.
• In Wilmington, dry air moved in and storms decreased, but they actually did increase a later, so it was kind of inconclusive in this case.

GOES-R Convective Initiation

• Some times it was giving lead time of 30-45 minutes, other times it provided no lead time.
• It was more useful in rapid scan mode.
• I was very impressed with its performance, but sometime the lead timne just wasn’t worth it.
• I thought this product was really great during the daytime, but I do not see it being at all useful at night as it was very inaccurate.
• It was sometimes hard to get a sense of what the probs meant. If I used it, I would get rid of everything under 50%. I just don’t like that much clutter.
• It was particularly erratic around the Appalachian mountains.

Prob Severe Model

• It works awesome in hail situations. I am a fan of it for hail detection and determining which storms will produce hail
• It does have issues with linear storm modes.
• The best part for me was teh moiseover sampling and being able to look at the predictors. It really enhances your situational awareness
• It would be nice to color code the growth rates in the readout
• I noticed a lot of sat growth rates that were older than an hour, that mad eme lose confidence in the signal.
• I think it did increase my confidence in hail events, because I was saw a clear progression in probabilities
• When I saw over 80%, I had great confidence that that storm would become severe
• I do think it could give additional lead time to warnings
• I am fine with including the lower probs because the display is not obtrusive, and I like seeing the progression to higher probs.
• I think what you have now, for hail I would use this product today.
• The survey questions were good
• It gives you a good idea of which storm(s) you should be interrogating
• All participants agreed they would use this in their local WFO.
• Broadcaster: I would use this on the air. If there were a lot of cells, I would point to this storm [with the higher probs] and say that that is the cell to watch. Would not necessarily show probs, but could show colors, etc.

Overshooting Top Detection

• This was not useful for me.
• I see this being most useful when incorporated into another product. This would be a great benefit
• We were unable to use it at night when it is harder to see OT’s, and when many more OT’s are often detected as storms have matured.

PGLM

• I really like the total lightning data
• I’ve never used total lightning, bit I do like it

Lightning Jump Algorithm

• I think I could use this in a warning environment.
• I don’t mind the sigma values as indicators.
• An outline (like prob severe)  might be better then the blob
• It might be good to incorporate the LJ product in the prob severe tool
• I don’t see the zero sigma being necessary
• I told AWIPS-II to blink sigma values that were greater than 2.

Tracking Tool

• There are too many circles on the screen, too much clutter.
• I would prefer to have one circle that you just put on the cell, and it gives you the meteogram.
• Entering the cell id # to track the storm might be a good idea
• I don’t really mind the circles, but I just can’t see myself using this in a warning situation.
• I can see this being used after the fact, looking at a storm, but not in real-time. It is too labor intensive.
• I like the graph itself, but the actual functionality is bad. 
• It is difficult to move the circle-track to align with the track of the storm, especially when many images are loaded. Also, sometimes it does not track at first, so you have to move it around to get it to track. Finally, changing the size of the circles is frustrating, as making some circles bigger makes other smaller. 

GOES-14 SRSOR (1-minute imagery)

• It's great!
• I saw subtle boundaries that I wouldn't otherwise see
• We want quicker satellite updates, it's a no-brainer
• No worry about information overload with this
• I will prefer to view the raw data, but I do see it being useful as input into other products as well

Other:

• I thought the training was good.
• The week was very well organized, well done, and I liked that we stuck to the schedules, it made things very easy.
• I liked the relaxed environment
• Less structure was good, it gave us freedom to see what works well for us.

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

Forecaster notes strong ProbSevere in Arkansas

With the Little Rock radar down all afternoon, a forecaster working the warning desk in Shreveport, LA, noted a strong ProbSevere value on a storm in central Arkansas. This storm exhibited strong satellite vertical growth and glaciation rates at 22:45 UTC, jumping the probability of severe from 8% to 36% (see animation below). In a marginal environment, the MESH slowly increased to 0.76", most likely an underestimate, on account of the missing KLZK radar data.

The forecaster said that using the strong satellite growth rates and MESH information from ProbSevere, the available radar tilt data from KSHV and KSRX, and the history of how other storms have evolved in this environment, he would have issued a severe thunderstorm warning for quarter-size hail (he was on the warning desk in Shreveport, so he could not issue an experimental warning).

The ProbSevere probability for this storm first exceeded 40% at 23:00 UTC, which has been very high for the environment today. This was 24 minutes prior to an official NWS warning at 23:24 UTC (figure 2). The ProbSevere eventually exceeded 80%.

Figure 2: NWS warning issued at 23:24 UTC.

-Cintineo

Synthetic Water Vapor Imagery (lower left pane) handles observed “Water Vapor Hurricane” (lower right pane) over Iowa fairly well.

Synthetic Water Vapor Imagery (lower left pane) handles observed “Water Vapor Hurricane” (lower right pane) over Iowa fairly well.

Shawn Smith

Simulated IR imagery vs. convective cells in DC

The simulated IR imagery showed the cold front’s areas of convection on the leading edge of the storm in our target area of Virginia and Maryland on Thursday afternoon.



It matched up spatially with what we were seeing in reality on the rapid scan GOES IR imagery at the same time stamp, 20Z.



The area in blue on the simulated IR indicates cloud tops colder than -60C. This shading doesn’t show up on the real IR image at all, but the cloud tops do have temperatures below -50C in the same convective regions. It looks like the simulated IR is going to overdo the convection, especially for the southern cell over central Virginia, but I thought I’d keep an eye on it to see if a convective cell spawned a severe warning in that area.

The simulated image valid at 21Z shows the strongest convection has shifted further east and is concentrated into one cell.



That cold cloud top maximum in northern Virginia is much smaller and not nearly as cold in the real GOES IR image from 21Z.



During this time period, a line of strong to severe thunderstorms was pushing through the DC Metro area.



Comparing the radar data to the simulated IR at the same time stamp, it appears that the small clusters of convective cells were not well resolved by this product. In fact, the clusters of storms to the south and west of DC were either completely missed by the simulated imagery, or the placement was off by about 50 miles (clouds too far to the southwest to be a match for the convective cells).

This was a day where we had limited tools for severe weather forecasting in the DC Metro area. The threat for hail and tornadoes was very low. ProbSevere, convective initiation, overshooting tops, and PGLM products were rendered useless because of a lack of convection and lightning parameters.

ProbSevere in a low-topped storm environment

In the mid-Mississippi River valley, storms slowly began popping up in an environment characterized by low MUCAPE and moderate to higher effective shear. Cold air aloft has generated enough instability to initiate storms, however. ProbSevere has generally forecasted 5-30% probabilities of severe for storms in this region (see animation below), exhibiting differing degrees of satellite growth and MESH.

Thus far, only 2 severe hail reports have been recorded in Arkansas. ProbSevere's forecasted probabilities have generally been in a neighborhood you would expect in this environment -- marginal. As might be expected with many storms with low probabilities, few reports have been observed (two severe reports thus far). Several penny to nickel size hail reports and sub-severe wind reports have also been recorded.

The storm with the 1" hail report had a 9% probability of severe (it was not warned by the NWS), and the storm that produced golf ball-sized hail had a 38% probability of severe 7 minutes prior to the report (not shown), and coincident with an NWS warning.

The images below show cases where there have been a some "correct nulls" for ProbSevere. In the first case, ProbSevere only had a 4% probability on a storm in Arkansas, when the NWS issued a warning. It never produced severe-level weather. Similarly, the second case below shows a ProbSevere contour near St. Louis, MO, with only 4% probability of severe when it was warned. No reports were recorded from this storm either.

Example 1:

 Example 2:

-Cintineo

FINALLY! A Lightning Jump Detection

Finally on our last day of EWP operations we were able to capture a weak lightning jump with the Lightning Jump Detection Algorithm. This jump was detected from a discrete cell that was lifting north across the western edge of the District of Columbia around 2109z. The jump from 0 sigma to 1 sigma (or 1 Standard Deviation) shows up as the green blotch on the image above. This is overlaid on top of the Flash Extent Density product which measures total lightning in the storm. At this time in the image above the flash density was 10 flashes per km^2 which was overlaid on 0.5 deg KLWX reflectivity of around 52 dBz.

The Tracking Meteogram Tool was used to see the evolution of the Lightning Jump, reflectivity and Flash Extent Density verses time. The take home from this is that a lightning jump or rapid increase in Flash Density within a storm correlates with a rapid intensity of a storm. Note that between 21:06z and 21:08z the Flash Extent Density rapidly increased or “jumped” from 1 flash/km^2 to 10 flashes/km^2 which triggered the Lightning Jump Detection Algorithm to increase from 0 to 1 sigma. During this time the dBz values of reflectivity increased from 20 dBz to greater than 55 dBz in 8-9 minutes. This cell was also somewhat low-topped with echo tops only reaching to around 32kft. Please keep in mind that this is a weak example of just how rapidly a cell can intensify since the jump was only 1 sigma.

Shawn Smith

ProbSevere Underestimates Storm in N AR on May 15

The storm below produced golf ball size hail (around 1.75 in diameter) and had 50 dBZ up to 31157 ft MSL from SRX radar (114 nm to the west southwest). ProbSevere only indicated 13% for severe with 1049 J/kg, 25.4 kt of EBShear, and 0.60 in MESH.  The lack of nearby radar data with the LZK (Little Rock) WSR-88D being inoperable may have significantly impacted the ProbSevere algorithm.

ProbSevere seems to again be underestimating the severe potential and expected hail size.  The environment was characterized with low topped severe storms with mid/upper trough overhead.  The 12Z LZK sounding is below as the last image.

Nearcast Tool – Convective Coverage

Above is the NearCast imagery at 22Z.  Utilizing this imagery, a pretty apparent boundary is evident across portions of MO into northwest Arkansas.  Along this boundary, convection was much more widespread than it was further south.  Further south, despite better instability, there is no indication of any boundary which likely explains the more scattered nature of the convection.  Operationally, seeing this boundary on the nearcast model would give me higher confidence in convective coverage further north versus further south.

22Z National radar Imagery (super hi-res :P)

Forecaster thoughts on how to use ProbSevere

A question was posed to the forecasters today: "How would you use a product like ProbSevere in your warning decision process?"

A common response was that the product is unobtrusive and readily overlaid radar data (all tilts or other radar products). Having a quick look at the CAPE, shear, MESH, and satellite growth rates with a simple scroll-over has been helpful.  ProbSevere can give forecasters a brief overview of which storms to watch and consider more carefully. It seems to have the best utility when considering large hail, and may struggle in environments conducive to low-top storms. The satellite growth rates have helped somewhat this week, highlighting storms before robust radar is present, but may have more utility in rapidly growing storms.

-Cintineo

Pre-frontal Virginia convection

A few storms have fired ahead of the squall line in northern Virginia. While most storms have had very low probabilities of severe (via the ProbSevere model), one storm had a 37% probability (figure 1), owing to 0.87" of MESH, 1220 J/kg of MUCAPE, and 27 kts of effective shear. The IR and visible GOES-East imagery showed that there was a very thick cloud mass over the mid-Atlantic, damping the satellite growth rates. However, 8 minutes after the ProbSevere exceeded 30%, the NWS issued a severe thunderstorm warning (figure 2). Fourteen minutes later, a wind report was recorded in northern Virginia. This demonstrates that ProbSevere was able to identify the "storm to watch" in this region, and the probability of severe could have been aided by earlier temporal information from the satellite growth rates, if they had been observable.

Figure 1: ProbSevere highlights a storm with 37% probability in Virginia, in midst of storms with 1-10% probabilities of severe. This storm later produced a severe wind report, while the lower probability storms have had no reports.

Figure 2: NWS warning (issued at 3:50pm). 

-Cintineo

Simulated Satellite Imagery Perspectives OK/AR on May 15

The simulated satellite imagery performed okay, generally capturing the overall IR and water vapor patterns.  The simulated IR and water vapor depicted linear convection too far south across Arkansas while the actual imagery depicted convection over northern Arkansas.  This product may be more useful for a National Centers such as SPC and WPC which cover the entire nation, but may be a bit too general for a local WFO which relies heavily on small scale features.

Michael Scotten

CI Tool Shortcomings -Thursday 1945Z

I noticed today that with the satellite out of rapid scan mode, the CI tool has not been nearly as effective.  It does not give the type of lead times that we had seen in rapid scan mode.  Here is an example:

1945Z satellite imagery with the CI tool overlayed.

In the above imagery, try to focus across the northern CWA (near the chimney region).  As you can see, very low values of CI are being detected at 1945Z.

Satellite with CI tool overlayed at 20Z.

I’ve circled the area of interest here.  By this time, there’s one small area of 50-60% dBz.  However, at this time, echoes were already beginning to show up on radar.

Satellite imagery with CI tool at 2015Z.

The probabilites finally began to expand and increase in this scan.  However, by now, the radar already had 30+ dBz echoes, which gave very little lead time to the probability of CI.  Given this is a cold core convective case, perhaps the threshold of CI is lower?  I noticed the other day 70% and above tended to result in CI, but perhaps in these type of environments the CI thresholds may be 50-60%.  Either way, it appears that without rapid scan mode, this product’s utility and ability to increase lead time to convection is greatly diminished. Below is the radar slice at 2019Z which corresponds to the latest satellite/CI imagery seen above.

Radar image at 2019Z.

ProbSevere not working out for bowing low-topped liner convection

In the 4-panel image above from 1955z over northern Virginia the ProbSevere model was evaluated on a low-topped bowing line of storms. The developer has noted poor performance in liner convection but wanted to evaluate its utility in storms with damaging winds.

The top left pane shows 0.5 deg reflectivity from LWX radar with the ProbSevere model shapefile overlaid. The top right pane shows 0.5 deg velocity and the lower left pane is enhanced echo tops. The mouseover shows inbound velocities of around  50kts at the nose of the bowing convective line with enhanced echo tops only to 20kft (low-topped). This line of storms is likely producing some damaging winds but the low-topped nature of the convection should preclude any hail. The ProbSevere shapefile of predictors indicated only a 1% probability of a severe storm in an environment with 620 J/kg of MUCAPE and a healthy 36.2 kts of EBShear (High Shear Low CAPE). The MESH product is likely performing well since it only indicated hail to 0.08 inches. This case further supports the lack of utility of the ProbSevere model in liner convection. However, I continue to feel that its best use is for detecting storms which can produce severe hail.

Shawn Smith

On the Usefulness of the GOES-R Convective 4-Panel Procedure

A 4-Panel created by Bill incorporating many of the GOES-R Products

Just a quick post to discuss the utility of this convective 4-panel.  Operationally speaking, I can forsee this procedure being quite useful as it incorporates many analysis tools.  The NearCast tool (top left) can be looked at and compared to ongoing cloud cover/convection to see if storms are forming along/near any boundaries.  In this case, you can see that convection is concentrated in the most unstable airmass, located across Arkansas northwest into eastern Oklahoma.  It is also nice to have the CI tool (top right) with this procedure to diagnose if any of these boundaries have convective potential in the near-term.  I added radar to the bottom-right panel in order to see convective trends and whether or not CI is actually occuring in some of the areas highlighted by the CI tool.  In this case, the overshooting top tool did not have any detections, but would also be of use with more robust convective elements.  Overall, I think this procedure will be of operational use, especially once GOES-R is actually launched and these products increase in overall utility.

- KD

ProbSevere Too Low in Cold Core Low Events with Low CAPE/Marginal Shear

The top image below depicted a few marginal severe storms in western Arkansas,  The storm of interest is the one farthest west between the two other cells that were located slightly to the east.  ProbSevere gave this storm 9% chance of being severe in an environment with 898 J/kg, 27.4 kt of ENShear, MRMS MESH of 0.53 in, 1.27%/min normal vertical growth rate, and 0.03/in glaciation rate.

This storm produced quarter size (1 in diameter).  MESH underestimated the hail size in this case.  I (as well as the WFO Little Rock) did not issue a warning of this storm thinking the hail size was a bit smaller (closer to pennies – 0.75 in or nickels – 0.88 in).  The environment was characterized by the 12 UTC LZK (Little Rock) sounding below (bottom image) with a freezing level of 6579 ft AGL and -20C level at 15572 ft AGL, conducive for the development of hail.

The ProbSevere seemed to be too low in this case, only with a value of 9%. I would personally estimate the ProbSevere closer to 30 or 40% for this storm, especially considering that the reflectivities 16-17 kft AGL were 55-60 dbz (I typically use 60 dbz or greater at the -20C level as a proxy for issuing severe thunderstorm warnings for large hail.)

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