Elevated September Storms

Thunderstorms developed in southern Iowa early Monday morning along a warm frontal boundary. The MLCAPE was 0 J/kg, while the MUCAPE across the baroclinic zone was 800-1000 J/kg, indicating that these storms were not rooted at the surface. The effective bulk shear was also considerable, at 45-50 kts. The storm featured below had strong satellite growth rates at 11:15 and 11:30 UTC, which contributed to an elevated probability of severe (44%) when the MRMS MESH was less than 0.5". The ProbSevere model showed probabilities increase to 84% (12:04 UTC) and 96% (12:14 UTC), as the MESH increased to 0.81" and 1.27". This storm was never warned, while one-inch diameter hail was recorded in Appanoose county, IA at 12:55 UTC, 51 minutes after the first probability of severe greater than 80%. This example demonstrates the utility of the ProbSevere model in perhaps giving forecasters a "heads-up" on storms to watch in a set-up where severe weather was not expected.

John Cintineo

UW-CIMSS

NOAA/CIMSS Prob Severe Examples from September 9 2014

A strengthening frontal boundary extended from Lake Superior to the western High Plains on Tuesday, September 9th, while a surface warm front extended east from developing low pressure in Kansas east to central Illinois.  A vigorous mid-level short wave was moving across western and central Nebraska at the time resulting in the strengthening low pressure and cyclogenesis.  Deep column moisture was located to the south of the warm front with surface dewpoints in the lower 70s and precipitable water values of 1.5 to 2 inches.  Moderate to strong instability was in the frontal zone along with moderate effective bulk shear.  

Several strong thunderstorms developed during the early afternoon in the vicinity of the warm front. A line of thunderstorms moved across southwest Iowa toward Des Moines during the early afternoon. The below image from 1816z shows this line of thunderstorms to the southwest of Des Moines.  The CIMSS Prob Severe product was indicating a 69 percent chance for this line of thunderstorms to become severe in the following 60 minutes.  The thick cirrus anvil from this thunderstorm prevented the Vertical Growth and Glaciation Rate information from being determined.  

An examination of the KDMX all-tilts products and digital VIL indicated more of a threat of strong winds over large hail.  However RAP forecast soundings showed a strong thermal inversion around 1500 feet.  The KDMX velocity imagery indicated approaching 50 to 60 knot winds approaching Des Moines along the radial.  However, the CIMSS Prob Severe product lowered the severe probability to around 30 percent as the line of storms approached Des Moines.  A severe thunderstorm warning was issued for the counties to the west of Des Moines. The thunderstorms moved through the Des Moines area around 1915z uneventfully as the inversion prevented the strong winds aloft from mixing down to the surface. 

Another batch of thunderstorms strengthened over eastern Nebraska during the early afternoon. These thunderstorms approached the Omaha area and produced a wind gust to 55 knots at Fremont Nebraska (KFET) at 1955z which is about 30 miles west of KOMA.  The CIMSS Prob Severe product from 1948z indicated only an 8 percent chance for this thunderstorm to become severe in the next 60 minutes.  Again, the Growth and Glaciation Rate information was not available.  

The above two examples illustrate how the CIMSS Prob Severe product is geared more toward forecasting a large hail threat using available instability parameters, especially when satellite information is not available.

Marc Kavinsky
NWS Milwaukee/Sullivan

John Cintineo
UW-CIMSS

Upper Midwest storms and NOAA/CIMSS Prob Severe Model Demonstration

The GOES-R PG CIMSS/MKX shift focused on the Upper Mississippi Valley on Thursday, September 4.  Ongoing convection existed over far northern Wisconsin early in the morning on Tuesday.  The storms were discrete, elevated supercells that eventually congealed into a linear convective system.  While the NOAA/CIMSS ProbSevere model is designed to increase lead-time to the initial severe warning/hazards, this case demonstrates what others have noted during the spring and summer this year, that the ProbSevere model performs well with discrete mature convection.  Figure 1 below is shows the Green Bay 0.5 degree reflectivity with NOAA/CIMSS ProbSevere model output in the shaded contours around storm cells valid at 1452 UTC 4 September 2014.  These two storms with high ProbSevere values (> 90%) produced golf ball sized hail around this time.

Figure 1.  KGRB 0.5 degree reflectivity and NOAA/CIMSS ProbSevere output valid at 1452 UTC 4 September 2014.

Not shown was the progression of these storms across northern Wisconsin in the morning hours on Thursday.  During this time the ProbSevere values were consistently high (> 85%) with sporadic severe reports across the rural Northwoods.

Additional elevated storms developed over western and southwestern Wisconsin during the early afternoon hours, fueled by warm air advection.  These storms struggled to develop as the atmosphere was strongly capped.  The ProbSevere values associated with these storms remained (correctly) quite low over southwestern Wisconsin.  The storms over west-central Wisconsin did exhibit higher probabilities, as much as ~60% (largely due to much higher values of effective bulk shear and MRMS MESH values approaching 0.75"), but as of this writing have yet to produce severe weather.

The strong cap in place is likely to inhibit surfaced based convection along the cold front in Minnesota through the duration of the shift.

-Justin Sieglaff (UW/CIMSS)
-Ben Herzog (NWS MKX)

FROPA convection on the Plains

Strong early September convection fired on a trailing cold front in the late evening and overnight hours in northern OK, southern KS, and southwest MO. The environment near and along the front was characterized by MUCAPE ~2500-4000 J/kg and effective shear ~20-35 kts. The IR-derived satellite growth rates, as captured by the NOAA/CIMSS ProbSevere model were very strong, during this period of GOES-East rapid-scan operation.

GOES-East IR brightness temperature, 5-minute NLDN lightning plot, and METAR station plots.

 The explosive growth rates, along with strong MRMS MESH and a favorable environment, led to very high probabilities of severe (80-100%) before severe weather was reported from many of these storms.

ProbSevere contours overlaid MRMS reflectivity and NWS warnings.

 The first storm to initiate in south-central KS (shown below) went from 10% (22:30Z) to 57% (22:34Z) probability of severe as the observed satellite growth went from moderate/weak to very strong, while the MESH remained constant at 0.25". Six minutes later, the probability of severe was 79% (MESH still < 0.5"). By 22:52Z, the probability of severe exceeded 90%, as the MESH was nearly 0.75". The probability maxed-out at 100% at 23:14Z, when the MESH was 1.47" and the first 1" report was also recorded at this time. This storm would go on to produce a large tornado near the town of Cedar Vale, in Chautauqua county, as well as baseball-sized hail in Winfield, KS.

The storms in the region produced numerous severe weather reports, including hail up to the size of baseballs, wind gusts up to 80 mph, and large tornadoes. The satellite growth rates from the model may increase forecaster confidence in issuing warnings and perhaps increase lead-times to initial severe hazards.

John Cintineo
UW-CIMSS

Severe Hail in Texas Panhandle

All day we were watching weak convection along a cold front in the Central Plains and ProbSevere as expected with these weak storms was no higher than 5 percent. Later in the afternoon, a few isolated cells in the Texas Panhandle rapidly developed. One storm, the Clarendon storm, became severe within an hour of initiation. We utilized ProbSevere as guidance in determining which storms to focus on for potentially severe hail. ProbSevere made it easy to see the evolution and intensification of the individual cells. Eight minutes before the Clarendon warning, ProbSevere was 43%, two minutes later it was up to 72%, another 4 minutes later it was up to 96%. At warning issuance another 2 minutes later it was 98%. ProbSevere performed well with regards to hail size. During this 8 minutes the MESH increased from .71 to 1.8 inches. After the warning was issued, it continued to increase to 2.4 inches. Local storm reports of 1 to 2.5 inch diameter hail were received.

Nearby cells that were developing around this time had a ProbSevere of 80-98%, however none of these cells had a warning except for the Clarendon storm during the initial time period studied. A half hour later the warning over the Clarendon storm was expanded to include most of the nearby cells that ProbSevere had high probabilities for earlier. There were no storm reports issued as of 15 minutes into the warning for the other cells but regardless there was a warning consistent with the ProbSevere guidance.

Sarah Marquardt and Sean Miller
NWS Milwaukee/Sullivan

Crop damage in South Dakota

The morning of August 14th brought a lone hailstorm to central South Dakota. The NOAA/CIMSS ProbSevere model  did not detect cloud growth from satellite, as the convection had been ongoing for some time. The MUCAPE and effective shear of the environment were also rather weak. However, the MRMS MESH product reflected the development of the storm, increasing from 0.71" --> 0.97" --> 1.19" --> 1.69" over the span of 6 minutes (14:50 UTC to 14:56 UTC). The probability of severe increased from 14% to 80% during that short time. The MESH soon after was in the 2-3" range (likely an overestimate, possibly owing to single-radar coverage), and hail of up to 1.25" diameter was reported to damage the local corn crop at 15:05 UTC. The model provided 9 minutes of lead-time to the initial hail reports (measured from the 80% threshold). This example demonstrates how crucial radar detection/diagnosis of storms is in the ProbSevere model, as well as to forecasters.

ProbSevere contours overlaid MRMS Merged Composite Reflectivity, NWS warnings, and local storm reports.

John Cintineo
UW-CIMSS

Satellite growth rate utility in ProbSevere

Convection fired in central Texas along a weak cold front on the afternoon of Monday, August 11th, in an environment characterized by very weak effective bulk shear (< 5 kts) and strong MUCAPE (2800-3600 J/kg).

In the first featured storm, the normalized satellite vertical growth rate went from 'moderate' to 'strong', and the storm-top glaciation rate when form 'weak' to 'moderate' at 17:22 UTC, as the probability of severe jumped from 18% to 61%, with the MESH remaining constant at 0.67 in. The probability then fluctuated between 40% and 60% before the storm was warned at 17:44 UTC with a probability of severe of 58% and MESH = 0.65 in. The fluctuation may have been a result of very low shear and therefore a more "pulse" nature of convection. The satellite growth rates in this storm signaled enhanced probability of severe weather, whereas the shear and MESH were poor to mediocre. This storm was warned again at 18:39 UTC and attained a maximum probability of over 80%. Thus far, there have been no LSRs for this storm, located about 100 miles southeast of Dallas-Fort Worth, TX.

The second featured storm to the southwest had strong normalized satellite vertical growth and glaciation rates at 17:45 UTC. The probability of severe increased from 28% to 72% to 92% from 17:58 UTC -> 18:00 UTC -> 18:08 UTC, as MESH also increased from 0.46 in. to 1.13 in. over that time. This storm was warned at 18:16 UTC and had a severe wind report at 18:18 UTC (trees blocking intersections).

The third storm featured to the northeast of the first storm also had strong satellite growth rates (it was under the same parent satellite cloud-object as the first storm) before rapidly attaining a probability of severe of 86% at 18:56 UTC (MESH = 0.9 in.). It was severe-warned at 19:03 UTC and had a 1 in. hail report at 19:10 UTC.

These examples show how temporal trends in satellite-derived fields can help signal severe potential in slowly developing and more rapidly developing convection. By integrating satellite parameters (when applicable) with radar and NWP fields, we hope to paint a more accurate picture of storm evolution and initial potential severity.

ProbSevere contours around MRMS merged composite reflectivity.

EDIT: Several of these storms did have marginal wind and hail reports.

John Cintineo

UW-CIMSS

ProbSevere in SE Missouri

A high CAPE, low shear environment fueled convective development in southeastern Missouri during the early to mid afternoon on 6 August 2014. Rapid convective development was captured using the ProbSevere function as can be seen in this image.

Convective development over SE MO at 1936Z. ProbSevere values of first warned storm are shown. 0.5 degree reflectivity was captured from KLSX.

This image shows the visible satellite imagery of the same storms in southeastern Missouri. The storm had plenty of lightning associated with it as it tracked to the southeast.

Visible satellite imagery of SE MO. Note the numerous lightning strikes over this area.

At 1936Z, the severe probability was nearly 100% for the northeastern most cell. The MESH value was 1.84. The high CAPE environment allowed these thunderstorms to develop quickly (storms had moderate to strong satellite growth rates), and ProbSevere did a good job in diagnosing the cell as ProbSevere had severe probability values jump from 26% at 1930Z to 81% at 1932Z. Shortly after this spike, the NWS in Paducah issued a Severe Thunderstorm Warning at 1936Z.

At the time of this post, there were no severe storm reports that came out of this cell. This might be contributed to the environment not being as favorable for severe weather (the area was in a See Text severe category from the Storm Prediction Center). SPC did issue an MD for the area for sporadic microbursts shortly after the initial warning, and there were a few penny sized hail reports for a cell that developed over Poplar Bluff. The ProbSevere MESH value for that cell was ~1.14, with a ProbSevere value of 90%. The ProbSevere value was at least 90% for that cell for about five minutes prior to the first report of penny sized hail.

Schultz NWS-MKX
Cintineo UW-CIMSS

ProbSevere in Wisconsin marginal hailers

A departing strong upper-level system over the Great Lakes left an opportunity for storms to develop in a northwest flow regime over northern and central Wisconsin on Thursday, July 31.

Cool air aloft provided good mid-level lapse rates (~ 7 C/km) and associated instability for storms to tap into, coupled with decent low-level lapse rates.

SPC's objective analysis of mid-level lapse rates.

The environment was characterized by ~1500-1900 J/kg of MUCAPE and ~15 kts of effective bulk shear. The AWIPS-II scroll-over readout of the NOAA/CIMSS ProbSevere model contours showed that these storms had strong normalized growth rates and glaciation rates, two or more hours prior. Development on radar lagged the strong growth observed from satellite, in this case. Storms developed MRMS MESH values of 0.7 to 1.15". The MESH, coupled with the satellite and environment information yielded probabilities of severe in the 60-90% range. These storms highlighted below were warned 15-25 minutes after ProbSevere exceeded 50%. The storms in Portage and Barron counties produced 1" hail, while the storms in Burnett and Clark counties had no reported hail. 

While radar is the most valuable stand-alone tool for severe storm analysis, this case highlights the use of the satellite growth rates in the fused product to enhance confidence and lead-time to severe hail. 

ProbSevere contours overlaid MRMS Composite Reflectivity and GOES-East visible imagery.

John Cintineo
UW-CIMSS

ProbSevere MRMS fields vs. Single-source radar fields

NOAA/CIMSS ProbSevere display with kapx 0.5-degree Base Reflectivity, 1744 UTC on 22 July

Note the radar object above, enclosed in purple, from the MRMS (Multi-radar, Multi-sensor) fields, differs from the 0.5 Base Reflectivity field from the Gaylord, MI radar displayed.  This is to be expected because the MRMS is composite reflectivity from a variety of radars (in the case above, likely Gaylord, Marquette (MI) and Green Bay (WI)).  Do not expect a field from a single radar to overlap the MRMS fields.

(Scott Lindstrom, Ben Herzog)

Severe Storms in Northwestern Arkansas

As the CIMSS/MKX GOES-R Proving Ground shift wound down Tuesday afternoon, severe thunderstorms rapidly developed over northwestern Arkansas.  This region was supportive for strong to severe thunderstorms with MUCAPE between 2500 and 3000 J/kg and effective bulk shear 20-30 kts.  Figure 1 below shows the NOAA/CIMSS ProbSevere Model overlaid on MRMS composite reflectivity.  Of note is the rapid increase in the ProbSevere values over the course of 6 minutes between 2032 UTC and 2038 UTC 08 July 2014.  At 2032 UTC the ProbSevere value was 8%, then at 2034 UTC the ProbSevere value jumped to 56%.  This jump was attributed to more intense satellite growth rates (the normalized vertical growth rate went from 1.4%/min (strong) to 2.6%min (quite strong) and the glaciation rate increased from 0.02/min (weak) to 0.06/min (strong)) as well as a jump in the MRMS MESH associated with this storm 0.35" to 0.52".  Another four minutes later at 2038 UTC the probability jumped again to 95% as the MRMS MESH approached 1.00".

Figure 1.  NOAA/CIMSS ProbSevere Model and MRMS Composite Reflectivity over northwestern Arkansas during late afternoon of July 8 2014.

This example illustrates the increase in lead-time to severe hazards as well as severe thunderstorm warning issuance that is possible by quantitatively using satellite growth trends with environmental information and radar observations of a storm's precipitation core.  In this example, the initial severe thunderstorm warning was issued at 2059 UTC--20 to 25 minutes after the significant jumps in the NOAA/CIMSS ProbSevere output.   More storms continued to develop further west during late Tuesday afternoon, most of which became severe thunderstorm warned after reaching high levels of NOAA/CIMSS ProbSevere values.  Only one severe report was received with these thunderstorms, but one wonders if this is more related to the population of very rural northwestern Arkansas--with much of this region covered by state and national parks (Figure 2).

Figure 2.  Google maps showing the one severe hail report received with these storms (green 'H').  The very rural nature to the area inferred by this map makes one wonder if more severe weather occurred than was actually reported.

-Justin Sieglaff, UW/CIMSS
-Steve Hentz, NWS MKX

Low Topped Wisconsin Storms

The synoptic setting for Wisconsin July 7th 2014 featured a small shortwave in a mid level trough over the upper Great Lakes.  MUCAPE values ranged from 300 to 800 j/kg with 0-6 km shear around 25 to 30 kts.  Scattered thunderstorms developed by noon.  SCAN max hail values were from 0.50 inch to 0.75 inch.  The CIMSS probabilities over severe were mainly in the single digit to around 25%, but many storms did have strong vertical and strong glaciation rates.  One storm did approach severe criteria. Using FSI with the Donovan technique a narrow core of 50dbz did just reach severe criteria.  The CIMSS Probability of severe was low at 49% , with the MESH value around 0.50 inch,   giving confidence that the storm was not severe.

-Steve Hentz

ProbSevere over the Mid-Atlantic and Southeast, 11 June 2014

We lost the NOAA/CIMSS ProbSevere feed at the National Weather Sevice (NWS) Milwaukee/Sullivan, Wisconsin (MKX) at 1742 UTC 11 June 2014. This was due to a communications failure at the National Weather Service Central Region Headquarters. So, we could not use and save the AWIPS II radar imagery with the CIMSS ProbSevere product.

However, we were able to save the images below from the ProbSevere website. These images were of convection in the Mid-Atlantic and Southeast U.S. from the early afternoon hours on 11 June 2014. We could not zoom in on the individual storms to get actual values from the ProbSevere product, so I'll just give some general trends on how it performed. Scattered convection developed across the region in a moist, unstable environment with 1000 to 2000 J/kg of MLCAPE, and 0 to 6 km shear of 20 to 30 knots. 

Convection developed fairly rapidly, and the ProbSevere values increased quickly as well. They seemed to show the rapid intensification of these storms well. Several Severe Thunderstorm Warnings were issued (yellow polygons) after the ProbSevere values increased rapidly. The ProbSevere product seemed to show some lead time to the issuance of the Severe Thunderstorm Warning products.

I have used the ProbSevere product in a couple of convective events in 2014 across the MKX forecast area. It was a useful situational awareness tool when convection first developed, until the anvils overspread the area. After then, it seemed to show more false alarms.

I would like to see an option to show the probability of tornadoes, severe hail, severe wind and flash flooding, if possible. Anything to help with situational awareness with flash flooding situations would be very helpful. It would also be good to try and keep the readout from the ProbSevere product from getting too cluttered with information. The color scale may need to be modified to one that has more colors at the higher end of the ProbSevere spectrum. This would help with seeing how high the value actually is.

This was a helpful learning experience, and look forward to more in the future!

Thanks,

JJW, Forecaster

NWS Milwaukee/Sullivan, WI

Contour colors: Blue - 1-9%; Cyan - 10-29%; Green - 30-49%; Orange -  50-69%; Red - 70-89%; Pink - 90-100%.
Polygons: Yellow - severe thunderstorm warning; Red - tornado warning; Purple - special marine warning.

Week 4 Summary and Feedback

Below is feedback from our final, week 4 weekly debrief session, along with a photo of the week 4 participants.

This marks the conclusion of the GOES-R portion of the 2014 HWT Spring Experiment!


- Bill Line, SPC/HWT Satellite Liaison

Simulated Satellite Imagery:
- It’s great to use the imagery to evaluate model performance.
- Had issues with burning off low stratus too early, leading to errors with heating during the day and errors of convection timing
- Do you see simulated model imagery being useful in forecast environment; would you like to see this data with other high res models?
    o All say yes, it is useful and would like to see it with other models (hrrr, etc)
    o Higher res models might pick up more discrete features things
 - Easy ways to pick up on errors in the model

Nearcast
- I used it mainly for ted and pw, it almost shows this better then anything I have in my office
- Nice to have in awips to overlay other things
- Helpful to show where boundaries will move, areas that are moistening
- Best as a precursor, ~3 hours prior to ci mostly
- I like the fact that you could really key in on boundaries, and I saw convection go there.
- Even subtle gradients up in high plains, small increases in ted, see showers pop up
- In Raleigh, having a tool that may easily show boundaries, esp in spring and summer, it could help
- I see more utility in theta-e and ted than in the PW field
- Calibration issue, we are used to looking at CAPE and LI. What does the ted values mean? Is there a way to do this?
- Its real-world information, which is good
- Overlayed forcing parameters on it.

Ci
- Didn’t increase my confidence as much as I had hoped
- One cell I tracked for a while in Huntsville area, had pretty high value, that did go up and eventually became strong
- Get rid of lower values

Probsevere
- This is especially useful for more slowly developing convection. Storms that look the same may have different probs, pointing out which storms are actually more threatening,
- Not as useful when convection is rapidly developing. The 1-2 scan lag hurts
- Good as a confirmation tool even for mature convection
- Good for slowly developing storms, detects hail well, poor with wind, not sure with tors. Prob severe hail may be better name. Rapidly growing convection, it wasn’t as useful with lag (1 volume scan), which hurt.
- Broadcaster – I really enjoyed this product. I am doing a lot during a day, especially severe day, it pinpointed where I should look. Same with CI
- Right now, as a regional SA tool, storms coming in from neighboring CWA, would be good to watch. Also for updating warnings.
- Column velocity to determine wind threat,
- Seems like product that has room to do some interesting things.
- with prob severe/hail/wind/tor, have a 4 panel, with total severe and 3 threats. Different parameter underlaid each

Overshooting Tops
- Broadcaster – really useful for me, in busy environment. I can speak for every broadcaster, we’d all love to have this product.
- More utility at night than during the day
- Helpful to CWSU cause I'm looking at a much larger area

Tracking tool
- This trend information is beneficial to have.
- Probably best for warning coordinator, or for research purposes. It is high maintenance, takes a lot of work to use

Lightning
- Broadcaster – lightning is especially useful for me, the chopper folks are constantly asking me where there is lightning to decide whether it is safe for them or not
- Most useful for rapidly developing convection
- Any time a jump occurred on a storm, the dBz’s would spike soon after
- I think it is everybody’s favorite thing, the lightning
- Most helpful for a warning operator, everything else was more SA.
     o Mostly because we had information every minute.
     o Getting additional info while we are waiting for next volume scan
- It impacted my warning decision making process.
- Especially useful in rapidly developing convection
- Broadcaster – lightning is very important even if it isn’t severe
- I wish I had more time to look at it.
- Training for lightning is not that good, to understand more why/how this is working, would be helpful. Why in certain environments and situations would it not work so well. But why better in others
   o Explain what is going in and why it is working

Broadcaster – from this perspective, most of the products demonstrated make it easier for him to do his job, because he can easily spot where a new storm is coming up in busy situations, where lightning is increasing. It helps make things easier for everyone at station.

CWSU – CI and OTD would be most useful for me, covering a broad forecast area. OTD quickly shows me where the strongest updrafts are, and ci highlights where convection is initiating or most likely to initiate in the near future. Also, lightning data is valuable for me.

General – be cautious of data overload. Products have to quickly prove their worth and utility in operations. Some products might be more useful for a warning coordinator, while lightning and maybe prob severe could be helpful for radar operator

Overall
- 1pm briefings from EFP, is there a reason for us to be in on that. A lot of it was not important
- Even from the briefings, I had no idea what was going on. It seemed more like a debrief for themselves. It had no application to us, it was geared to the efp
- I could have better spent my time making myself aware of the meeting.
- Schedule our debriefing during that, and maybe have it earlier (noon)?
- Since a lot is pre convective environment, we should come in at 9 or 10 to start.
- To be able to look at these products with other convective modes would be useful too.
- Broadcaster – recommend others to get with local wfo and get a couple hours in front of awips. Simuawips helped quite a bit.
     o This is most fascinating week of science I've had in a while.
     o Very much against working with just broadcasters in the hwt, found it very beneficial to be here with nws mets.
- All forecasters gained, learned from each others unique perspectives. Against segregated experiments.

Daily Summary: Week 4, Day 4 (5 June 2014)

Today, we operated in 3 county warning areas:

Team 1 (Fowle & Anderson)
Boulder, CO

Team 2 (Pelczynski & Satterfield)
Pueblo, CO
Huntsville, AL

Given the potential for cirrus-free skies and a lightning mapping array, we elected to operate in the High Plains where another upslope day was expected.  In particular, we chose the Pueblo and Boulder CWAs.  However, it became clear that the Pueblo CWA would wait to convect until later.  Given our time constraints (ended at 7 pm to start surveys), we decided to operate in the Huntsville CWA, where a very fast-moving MCS would move into a lightning mapping array.  Most of our experimental products were used, including the OUN WRF.  Several severe storms formed in both active CWAs, with multiple lightning jumps observed in both.

-G. Garfield
Week 4 Coordinator

Blog 13 June 5 HSV Area

Wind Damage in Sylvania (in Dekalb Cty) AL. OT Top detection correlated very well with this. 2245 OT Top detected damage report at 2311Z 5 June.1 sigma light jump at 2225Z as well!

2320Z D Satterfield

ProbSevere and S. Colorado Severe

The ProbSevere model captured the development of severe weather in southern Colorado nicely during the evening of June 5. With one cell in particular, the first probability over 50% provided 20 min lead time to the first reported severe weather (1″ hail).

The algorithm started tracking the cell at 2136 UTC giving it an initial probability of 9% (to the first severe, Fig 1). At 2210 UTC, the algorithm had its first probability over 50% with a prob of 65%, indicating the cell was more likely than not to produce severe weather (Fig 2). The first severe weather of 1″ hail was reported with this storm 20 minutes later at 2230 UTC (Fig 3). The probability had maxed out at 85% at 2216 UTC.

- Bill Line, SPC/HWT Satellite Liaison

Blog 12 June 5 HSV Area Cherokee County AL

In the last post I mentioned the prob severe as not as helpful today. We now have a cell in Cherokee county ahead of the MCS that has an OT Top detect and a 4 sigma jump in lightning. Prob Severe now at 80% with strong flash density. HUN has warned and with all of these present expect severe reports. In this case it was warned because of history of these storms but all of this increases confidence in the warning and that this storm is still likely getting stronger.. was not as impressive 30 mins ago.

DSatterfield 2255Z

ProbSevere Improvements

Couple quick thoughts on ProbSevere improvement – based on threats:

Wind:

T/TD depressions

Subcloud/Low Level RH

0-3KM Shear

DCAPE

Vertically integrated “core dump” e.g. track descending Z core

Hail:

Areal extent of negative ZDR cores on 0.5 degrees (difficult)

H7-H5 Lapse Rates

CAPE in Hail Growth Zone

500MB Temps

Tornadoes:

0-1km Bulk Shear

0-1 SRH

MLLCL



Fowle

CI tool not showing anything of real value here

The CI tool is really only keying in on the developing cumulus, which is seen easily in the visible satellite imagery. Since CI doesn’t work as well at night when the visible satellite is also not useable, it doesn’t appear to be adding value here. I think that perhaps having a lower limit on the percentages that show up would be best, especially if we are worried about potential for severe storms to develop. All in all I’ve found it somewhat useless today. As far as the location of the highlighted areas with respect to the actual clouds and increased reflectivities, they are slightly displaced to the west of center. A lot of the lower values don’t even result in any enhanced reflectivities.

-KP

-D. Satterfield

Blog 11 June 5 HSV Area Prob Severe Evaluation

Interestingly, today the prob severe with the large MCS that produced lots of storm reports including wind gusts to over 50 knots, and enough lightning to start fires, was not that helpful. I have circled a bow echo moving into GA from AL and also a line near the HTX radar (This storm was quite severe with high winds extreme lightning). OT top detection and flash extent density and light jump all worked well and were valuable members of the severe warn decision tree.

Not the case for prob severe, which could lead the forecaster to hold off on a warning if they overvalued it. I have used prob severe all week and had growing confidence in it for storm trends etc., but this is a lesson learned to consider its limitations.



D Satterfield 2251Z 5 June 2014

CI GOES-W vs E again

This is another example of GOES E vs W seeing CI. In this case, GOES-W showed a fairly large area of 79% while goes east showed little if anything. These clouds did end up developing into echoes well over 35 dBz within 30 minutes after these images were taken.

jca

Blog 10 June 5 HSV Area

Looking at the severe storms over North AL with 1km vis and OT detect overlaid.

The cell which has produced a lot of severe storm reports on the TN AL border is detected Storm near Chattooga Cty. GA (which moved out of Jackson AL) also has OT detected.

I have circled some obvious misses that are visible on the 1km vis. Storm near Boaz in Marshall AL has produced minor damage and high wind gusts and is also missed.

D Satterfield 2240Z 5 June

*** I looked closely at this case in the IR, and am surprised the algorithm didn't pick up on those misses. They were well within the thresholds (OT temp, anvil temp, difference), at least from what sampling of the storms I did. - BL

Prob Severe Tool Fail

Below are numerous images of the Prob Severe tool doing a poor job with severe winds in the Huntsville area and it had inaccurate location placement of the Prob Severe area as well. Perhaps the Prob Severe tool is best utilized for severe hail and possibly tornadoes, but it definitely did a poor job with winds.

-KP

Blog 9 June 5 HSV Area

Image lost do to network issues-

Have spent time tracking a cell ahead of the MCS over NE Al. Mainly in Jackson Cty. Little storm damage reports from it in-spite of lightning jump, and only a so-so reflectivity presentation. At 2130Z we do now have an OT top detection on this cell and it looks rather  impressive on vis imagery.

Did a 64 frame tracking tool analysis on the cell moving through Limestone AL and into Madison. This cluster produced 59 mph winds at KHUN and reports of lightning induced fires in Decatur area. Many reports of damage, trees down, and some building damage from strong winds. While the radar presentation was not impressive the track tool shows overshooting top detection at 2140Z with 5 sigma lightning jump at 2202Z. Flash density peaks at 2145 then diminished but then steadily rises to 60 at 2204.

Prob severe not much above 25- See post by KP for more on this. Good example here of flash extent and OT and lightning jump being a clue that this storm was severe. Radar look alone would be of little initial value, esp with no storm reports (late night hours for instance)

DSatterfield

lightning warning June 5

The lightning jump algorithm for the storm highlighted in purple went from -4 to 6…which is a significant increase over a 1 minute period. This prompted a warning.

jca

Example of cirrus obscuring CI

This loop provides an example of how the thin high cirrus clouds from the MCS to the northwest are obscuring the CI output for the cumulus clouds over Alabama. The edge of the cirrus shield is shown in the zig zagged line within the bubble.

-KP

*** The CI developers are able to track and give probs below thin and moderately opaque cirrus (likely with this case), unfortunately this was not observed/known till the final day so the simple change to the algorithm was not implemented in time for any evaluation. - BL

Pseudo Lightning Data

Today was the first day I had a chance to examine the pseudo lightning data.  We were watching storms just to the south of Denver.  The first lightning jump we saw occurred at 2017Z and jumped 4SD.  Still learning exactly how to use this – but was expecting an increase in storm intensity afterwards (based on the training) and this did occur.  ProbSevere gradually trended up as well – and using a combination of ProbSevere and the lightning jump data – issued a SVR at 2050Z.  Did not really examine the base radar data until after this – and based on dual-pol radar data – there was definitely hail falling by 2055 or 2100.

Thus – I considered the lightning data valuable.  It is another tool assess future storm intensity – i.e. which storm do I need to pay attention to.



Fowle

Blog 7 Day 4 on 5 June

Still watching storm over Jackson AL 4 sigma lightning jump. Reflectivity not all that impressive. but flash extent density and light jump are really popping.

prob Severe 84% but env shear weak.

MESH is at 1 inch. Hoping to get some spotter reports.

D Satterfield

Blog 6 Day 4 on 5 June

Suggestion on light jump usage.

Each to hi sown but I have found that putting light jump below Radar data works well. Spatial extent of Light jump covers larger area in smaller cells. Will not always work but on cells in which it does it seems handy. Example below. Basic suggestion here is to play around with hour you layer and display these tools.

The cell in Jackson cty AL has a 3 sigma jump and strong flash density.

DSatterfield

Blog 5 Day 4 on 5 June

Warning issued by HUN on storm in Jackson County AL. We also issued warning on it just before based on Lightning Jump/Prob Severe and flash extent density. These new products in my opinion really were valuable in knowing that this storm was likely to become severe. One of the best examples I have seen all week.

I suspect we were watching it sooner than even HUN was because of our experimental tools.