ProbHail Overestimating Severe Hail in Montana.

MRMS Composite Reflectivity over southeast Montana on Monday afternoon 2022 to 2136Z with ProbHail overlaid. Convection firing off near the Billings area with individual cells displaying high ProbHail values of 50 to 80 percent in the initial and mature phase of development. This was due to MESH values of 1" to 1.7". Issued 3 warnings for hail size of 1" but storm reports of only 0.25" to 0.88" were received before the storms weakened as they worked east of the Billings area.

- Jack Swigert

20:37z End Proof of concept test.

Have just ended proof of concept experiment.

2 severe warnings and a tornado warning were issued without (total) access to radar data. I was later informed that the lightning Jump algorithm currently uses radar for the constriction of spatial area.  Apparently there will be a satellite derived algorithm eventually that will restrict space without radar at a later date. This has a potential to be a big emergency backup procedure for use when radar goes down. 

The tornado warning was a lesser chance out in the middle of nowhere  for being issued as I requested internet streaming or live cam to get some kind of view underneath the storm for the warning based off of storm enviornment and Super Rapid Scan Satellite  boundary seen feeding into the storm.

Grant H.

Post Edit: Just wanted to add a picture from super rapid scan on the boundary the storm appeared to be riding.

Daily Debrief: 5/15/13

Yesterday turned out to be the best day of the experiment thus far! Later in the evening we saw rapid convective initiation in Southern OK and Northern TX. Supercells formed just west of the Dallas-Fort Worth metroplex and produced very large hail as well as a series of strong tornadoes in the area. Check out the image below of the pair of supercells just west of DFW. Tornados from these cells caused a lot of damage in Cleburne and Granbury.

051513 0036 UTC Reflectivity (top left), Velocity (top right), CC (bottom left), and TDS (bottom right)

A lot of blog posts and feedback were collected from this event on the various experimental products. Here are some of the comments noted in this morning's debriefing:

PGLM
- 'I noticed a correlation between the MESH and the lightning data. Several minutes after there was a big jump in flashes, there was also a big jump in MESH values.'
- 'The OUN network kept losing sensors so it was hard to know what was a jump and what was data loss. It would be helpful to have the status information so we know that we've actually lost sensors and and when we've got a jump.'
- 'In my opinion forecasters won't like that you have [use the lightning moving trace tool] manually.'
- 'In real time I can see [the moving trace tool] being a little clunky to use, a little labor intensive, but for analysis of an event it would be awesome to see that trending information.'
- 'It would helpful to see the lightning data plotted with the hail/MESH information.'
- 'We didn't hardly get any lightning with the Oklahoma bow echo... perhaps this could be an indicator that it wasn't going to be as strong of an MCS.'
- 'I paid attention to the lightning cores and where it was increasing significantly. This seemed to be a good indication of a strong storm.'

GOES-R CI
- 'There were a couple of times where the CI gave us an 80/90% value that developed/initiated into a deep convective core.'
- 'Values were overall low yesterday in TX, but where it pinpointed the higher values it did a good job of indicating strong initiation.'
- 'I thought it did extremely well. We were looking at a decent sized cu field and it seemed to pinpoint on specific cu very well.'
- 'Yesterday there was enough of a difference in the CI values where you could pick out the more significant initiation, but on other days it seems to be far more confetti-like.'
- 'THe Montague storm had a CI value of 60%. An hour later it initiated. Thirty minutes later we had baseball sized hail. Fifteen minutes after that we had a strong tornado.'
- 'It seemed to do well with the clusters of strong updrafts, but had trouble in higher terrain. This may be an elevation/snow effect.'

CTC
- We had good CTC rates on a number of storms that ended up falling apart. It ended up that the storms had good initiation but were moving into an environment not conducive to further growth.'
- 'The CTC did a good job yesterday, but it's still very important to know your environment. We saw strong signals, but not all initiated because of other environmental factors not seen in the CTC.'
- 'The CTC gave consistent lead time of at least 20-30 minutes for severe storms on multiple occasions [in Texas].'

Our last day of operations this week doesn't look to be nearly as exciting as yesterday. We're currently in the Goodland, KS, and North Platte, NE CWA's where things have already began to initiate, and may move further south later in the evening. Stayed tuned for further updates as the day progresses...

PGLM Flash Extent Density Comparison with MRMS Data

A lightning jump of 18 Flash/Min to 40 Flash/Min between 1908 and 1909Z with a second jump to 51 Flash/Min at 1912Z preceded a rapid increase in vertically integrated ice, MESH, and reflectivity at the -10C isotherm. A 1″ hail report was then acquired at 1926Z in Ratliff City.

The following plot shows the flash extent density trace for the storm approaching Ratliff City, OK. Focus on the timeframe between roughly 1900Z and 1930Z. Notice the strong jump between 1908Z and 1909Z.

MESH jumped from 0.63in (1910Z) to 1.10in (1912Z) to 1.26in (1914Z) with the last detection of 1.02in (1924Z) before dropping off thereafter. The following images show the jump from 1910Z to 1912Z.

051513 1910 UTC MESH

051513 1912 UTC MESH

Looking at the vertically integrated ice product…there was an increase in values from 14 kg/m2 (1908Z) to 20 kg/m2 (1910Z) to 32 kg/m2 (1912Z) with consistently high values above 30 kg/m2 through 1924Z. See the images below as the storm approached Ratliff City.

051513 1902 VIL

0501513 1910 VIL

051513 1912 VIL

Regarding reflectivity at the -10C isotherm…there was an increase to 59dBZ by 1912Z then 61dBZ at 1914Z (not shown).

Again, the 1″ hail report was acquired in Ratliff City at 1926Z which gives the lightning flash extent density tool a 17min lead time to the 1″ hail report.

RJM

Large CTC Values Providing Excellent Lead Time for Severe Hail

Developing supercells over the TX panhandle became severe appox 30 to 45 min after a significant CTC signal. This signal is shown below in the upper left corner of the 4 panel. 30 to 45 min. after the minimum CTC value of -33, MESH indicated 1 inch or larger hail. This is displayed in the second image below. Of note is how well the CTC algorithm is performing despite a modest cirrus shield.

Austin

Hail Lead Time from Cloud Top Cooling Products

As several storms developed in the DDC forecast area, and very slowly reached maturity (and severe intensity), the Cloud Top Cooling (CTC) product provided a significant amount of lead time.

CTC at 2202Z, showing strong indications in Lane, Clark, and Haskell Counties.

At 2202Z, three areas showed strong (20+) indications on the CTC product. The two areas in Lane and Clark Counties went on to produce severe thunderstorms. However, the smaller area in Haskell County did not end up with severe hail reports. All three of these CTC areas continued for several consecutive time steps.

CTC at 2232Z. A new area has developed in Ness County.

An hour and a half later, a new area of strong CTC developed in Ness County. This area also persisted for several time steps, and preceded severe thunderstorm development as the storm moved into Trego and Ellis Counties. The area near Haskell County was associated with the one storm that did not become severe, while the Clark County CTC area was associated with the severe storm moving out of Ford County.

With the exception of the sub-severe Haskell County storm, the other three CTC indications were associated with future severe hail reports.

Hatzos

Cloud Top Cooling rate Combined with MESH for Enhanced Lead Times

We continued to monitor Cloud Top Cooling (CTC) rates in combination with MESH from the MRMS to investigate a elevated storm in Sheridan County Kansas. CTC was able to provide 15 to 20 minutes of lead time before the MESH indicated .71 inch hail. Below is a four panel at 2115z of the CTC, instantaneous MESH, base reflectivity at KGLD, and 120 min MESH.

Four Panel: CTC, MESH, 0.5 refl. KGLD, 120min MESH

Continuing to monitor the storm, the HSDA has continued to indicate large (LH) to giant (GH) hail. With modest mid-level lapse rates (7.0-8.5 C/km) and decent mid-level shear, these storms continue to indicated mid and upper level rotation, indicative of large hail growth.

Guseman/Kurtz

Moderate CTC gives 25 min LT to 0.7" MESH

At 2045z the Cloud-top-Cooling product signaled a 12 C/15min value. This is on the moderate scale and validation study states that this value should lead to a 33 minute lead time to non-severe hail.

Upper right panel is CTC

At 2112z the MESH product signaled a 0.71″ Maximum hail size which is close to what the product is suppose to signal for the forecaster.

Upper right panel is MESH

Hampshire

GOES Hail Probability Product - Day 2

Complementing the blog post below about convective initiation in Minnesota, the image above shows the 21-00 UTC hail probability forecast on 10 May 2011. The units are %, and the small 'a' symbols represent observed hail reports. Note the maximum located in western and central Minnesota; as noted in the other post, storms were just forming at 21 UTC, and proceeded to produce severe hail a little east of their initiation point. Additional hail reports occurred later after 00 UTC. Notice also the maximum in eastern Indiana and western Ohio, and the observed reports there.

Hail Probability Product from 16 June

The image above shows the severe hail probability product from 16 June, valid from 21-00Z. Also plotted are the severe weather reports between 18-00Z; hail is denoted by 'a'. Only a couple of the reports in Montana occurred prior to 21Z, the rest being observed within the hail product's 3-hour time window. For reference, the 2115 UTC GOES-East IR image is below. The product did a nice job of highlighting the regions in which hail was observed (and other severe weather in the case of eastern Kansas). In particular, note the small region near Sydney, Nebraska. There, towering cumulus had just begun to form and a bullseye of probabilities can be seen. Hail was reported there around 2200 UTC.

Hail Probability Product

Data from yesterday's probability of severe hail product was examined. The image above shows the probability forecast (%) from 20 UTC, valid from 20-23 UTC. Also plotted are the severe reports, where hail reports are denoted by 'a'. NAWIPS requires all reports from 18-00 UTC to be plotted at the same time, so not all of the reports above occurred during the 20-23 UTC forecast period. Specifically, the 3 southernmost reports occurred after 23 UTC.

Cold cloud tops from GOES-East dominated the input parameters, but the instability from the SPC mesoanalysis and the RUC forecast contributed. Note that the majority of the hail reports fell within the 1% contour in west Texas, although not specifically within the maximum probability area. The second max across Oklahoma saw no reports; this is a weakness of the product....if cold cloud tops are observed over regions of moderate instability, as was in the case in Oklahoma, higher probabilities will result. I looked at earlier forecasts, and on this particular day the product did not provide a significant lead-time prior to the development of storms.

Missing data... now partially restored

Sometime last week, changes were made to the experiment's NAWIPS systems and the GOES-R Proving Ground Products SATCAST and Probability of Severe Hail were removed by an unknown party. I worked with the SPC IT staff to reincorporate the missing data into the NAWIPS systems... The Probability of Severe Hail is back up, but we are still trying to get SATCAST back up and running. The simulated satellite imagery, lightning threat, UWCI and OTTC products remained unharmed. Will keep an eye on this and work on getting the SATCAST back up and running.

Severe hail probability forecasts hail over central US

SPC 24-hour reports for 25 May 2010
3-hour severe hail probabilities for 2100 UTC on 25 May 2010
The severe hail probability product was examined this morning to determine what characteristics of what it showed following yesterday's widespread severe weather across most of the country. We noticed that the product performed well in forecasting the occurrence of severe hail over IA/IL/WI/AR earlier in the day, with probabilities exceeding 2% hours in advance of severe hail reported on the ground. Along the dryline in NM/TX/CO/KS toward the evening, the probabilities also were seen 1-2 hours in advance of severe hail reported on the ground, including one report of 3" along the CO/KS border. (see above images) The lead time slightly decreased along the dryline region where storm growth was much more explosive. This helps explain the decrease in lead time over this region as the product may not be able to detect these storms as far in advance.

Severe hail probability forecasts hail over OK

Severe hail probability forecast valid from 2200-0100 UTC and severe storm reports from 2100-0300 UTC on May 19-20, 2010

Yesterday's severe storms dropped baseball sized hail just south of Norman, OK. The 0-3 hour severe hail probability forecast picked up on the storms that dropped hail over Oklahoma after 0 UTC. On the attached image, severe hail is plotted as blue letter a's from 21-03 UTC... most of which occurred after 0 UTC. The probability forecast made at 2200 UTC was valid until 0100 UTC. The higher probabilities up north represent already tornadic storms occurring over Stillwater, OK that have had a history of producing hail in the past. The intensifying probabilities extending south picked up well the storms that would produce hail in the near future.