Comparing Storm Strength

NWS Wilmington had a strong t-storm statement for the storm crossing into Ohio.  The severe probabilities had increased rapidly, and in the text it stated:

Frequent cloud-to-ground lightning... 

The GLM did not match at the time of the statement being issued.  But then rapidly increased a couple minutes after.  So there was a little discrepancy and if you went by the GLM only, it did not look impressive for a strong storm or statement.  The storm is entering into a more impressive environment.  Possibly continuing to strengthen.  And if so, could become severe quickly based on the trends.  

-Penny Gardens 

Using GLM Flash Extent Density (and ProbSevere Model) to fcst a svr TS

I'm looking a bit out of the area I'm supposed to be monitoring, but a storm S of St. Louis caught my attention because of its isolated nature and because there was a 1" hail report from it at 2023Z. I decided to investigate just a bit...

From 1945Z to 2005Z, this storm averaged 33-41 lightning flashes/5 min (using the GLM Flash Extent Density product) over an area covering several "grid boxes", with ProbSevere Model indicating a ProbHail of 10% or less.

Then..

From 2006Z to 2016Z, there was a lightning flash extent density "jump", both in the number of flashes and the areal coverage of the max flash extent density, with the max # of flashes (well, flash extent density/5 min) reaching reaching 62 at 2010Z, 82 at 2014Z and a max of 94 in one grid box by 2016Z, which is when the ProbSevere Model finally reached a ProbHail threshold greater than 50% (57%). So, watching the GLM Flash Extent Density trend and noting the jump time, a warning forecaster could have potentially issued a warning approximately 10 minutes before the severe hail was reported, whereas the ProbSevere Model would not have given as much lead time.

Here are a few screen captures of the storm:

~ 2006Z:

~ 2012Z:

~ 2016Z:

- Thomas Bell

ABQ - First look at CI Probs

2145Z: Latest HRRR has backed off on convection this evening over southern NM, with the ongoing clusters north of ABQ likely remaining the main event. However, the last couple HRRR runs have suggested a lone supercell tries to develop across southern NM so decided to analyze the CI probability & Severe CI probability across this area.

The first issue was deciding which GOES satellite to use, east or west. Obviously I would prefer to use the higher spatial & temporal resolution with GOES 16, but the ABQ WFO is getting near the edge of the GOES 16 disk. Data is available in AWIPS for the astern half of the CWA (east of I-40) but I don't know how much I can trust the data this far from the nadir.

Looping through about an hour of data I see a lot of sporadic jumps in probabilities for both the CI & Severe CI products. On the Severe CI product gif below, values are generally low around 10% but the product will often jump up to 50% or even 100% & back to 10% from frame to frame. While the values overall remain low & no increasing trend is evident, the sporadic increases in data lead to lower confidence & trust in the data. Similar but less extreme jumps in values were evident in the baseline CI product. I did notice a slight trend in increasing CI probabilities but we're only talking from 10% to 30-40% so I'm no longer expecting much in the way of development across southern NM this afternoon. I really like viewing the CI data overlaid on GOES-16 Channel 2 visible imagery to better identify the cu clusters that may be the next to initiate.

I also looked at the CI & Severe CI probs from GOES West. It's tough going back to the coarse resolution & 15-minute imagery of GOES-15 when you've had a taste of the new & improved GOES-16. In our current GOES-16 world I guess I'm just too impatient to wait 15 minutes for data & it was hard to zero in on favored areas of cu development with the coarse resolution "blobs" . The values for CI & severe CI generally matched up well with the values from GOES-16 so that bodes well for the tuning of the GOES-16 product.

Svr Hail Report ABQ - A ProbHail & Flash Rate Perspective

[22:00 UTC] With the cluster of storms moving just east of the immediate Albuquerque area, ProbSevere (but more specifically ProbHail) remained high, but steadily increased in the 10 minutes or so prior to a severe hail report (1 inch in diameter) received from Bernalillo County. The report time was 20:42 UTC and the following was noted in the 10 minutes leading up to the severe hail report:

20:33 UTC: 
ProbHail: 67%
MESH: 0.73 in.
Flash Rate: 114 fl/min

20:38 UTC: 
ProbHail: 88%
MESH: 1.14 in.
Flash Rate: 129 fl/min

20:41 UTC: 
ProbHail: 96%
MESH: 1.55 in.
Flash Rate: 129 fl/min

At 20:46 UTC, the flash rate began to go down (to 117 fl/min), with a bit of a delayed corresponding drop in ProbHail and MESH (occurred at 20:49 UTC and later scans). 

Fig. 1: KABX 0.5 Z (UL), ZDR (UR), KDP (LL), and CC (LR)

ProbSevere

The ProbSevere is nice to have as a quick reference on which storms I need to watch.  I can prioritize where to watch for growth as a storm moves into a more favorable environment for wind/hail/etc.

I'm finding that some parameters won't load.  Not sure if it is because I have too many windows open with all the data coming in.  Trying to keep my work station simple so I don't crash the system...again.  *Local SVR warnings didn't pop up in my workspace when there was a severe t-storm warning.

I'm gravitating towards the GLM info to see how the storm is strengthening or dissipating.  The warned storm crossing into Ohio went to a strong signal for lightning (still not sure how to quantify).  Warning was issued at 21:05Z.  Here's the snapshot at 21:07Z (storm located near middle of each screen in 4 panel). 

 

At 21:25Z the warning was canceled early.  Here's the lightning snapshot at 21:13Z...some lightning data was missing. 

Here's the warning for reference.  

-Penny Gardens

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Wilmington OH
505 PM EDT MON MAY 21 2018

The National Weather Service in Wilmington has issued a

* Severe Thunderstorm Warning for...
  Northern Darke County in west central Ohio...
  Southern Mercer County in west central Ohio...

* Until 545 PM EDT.

* At 505 PM EDT, a severe thunderstorm was located near Union City,
  moving northeast at 30 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Minor hail damage to vehicles is possible. Expect wind 
           damage to trees and power lines.

* Locations impacted include...
  Greenville, Coldwater, Versailles, St. Henry, Union City, Fort
  Recovery, Ansonia, Osgood, Chickasaw, Burkettsville, North Star,
  Rossburg, New Weston, Yorkshire, Darke County Airport, Rose Hill,
  Maria Stein, State Route 47 at US Route 127, Eldora Speedway and
  Willowdell.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

To report severe weather, go to our website at weather.gov/iln and
submit your report via social media, when you can do so safely.

Large hail and damaging winds and continuous cloud to ground
lightning is occurring with this storm. Move indoors immediately.
Lightning is one of nature's leading killers. Remember, if you can
hear thunder, you are close enough to be struck by lightning.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4047 8446 4036 8445 4035 8444 4027 8443
      4009 8468 4015 8481 4034 8480 4048 8473
TIME...MOT...LOC 2105Z 211DEG 24KT 4021 8474 

HAIL...1.00IN
WIND...60MPH

Use of GLM Data in Radar Data-Sparse Areas

[21:30 UTC] As a cluster of strong to severe convection moves east of the immediate Albuquerque area, GLM data came in handy as the storms moved east of some terrain and the 0.5 beam from KABX became blocked (as seen in Fig 1. below). In fact, during this time, GLM flash extent density was increasing fairly rapidly, which would help forecasters in an operational sense when used in tandem with other datasets (such as MRMS composite reflectivity). In this case (as well as many others), GLM data provides a supplemental dataset for monitoring storm activity in the absence of traditional radar interrogation techniques.

 

Fig 1: KABX 0.5 Z showing beam blockage just east of the radar site.

Fig 2: GLM Flash Extent Density (flashes/5min) (UL), Average Flash Area (UR), Total Energy (BL) and GOES-16 Channel 13 (LR).

Rosie Red

Initial thoughts about the CI Probability Product

The CI Probability product is a bit of a "noisy" display with a lot of seemingly "random" areas of CI Probability percentages that percolate up and down, disappear, then reappear, etc., but...

If one filters through the noise and pays attention to areas where 2-3 (or more) consecutive frames display a CI probability of ~ 50-70% (or higher), it seems that convection with reflectivity values of at least 35 dBZ is more likely to form in those areas.

Maybe it would help to get rid of values below 50% on the color/percentage bar? That would filter a lot of the noise and make it a more useful product.

Also, perhaps using a different time-step (is 5 min too long or too short? I don't know...) or tweaking the algorithm a bit might help distinguish those areas more likely to experience convective initiation.

- Thomas Bell

ABQ - First Look at NUCAPS

2100Z: NOAA-20 has made it's pass over the central US so am taking my first look at NUCAPS soundings (non-corrected version). I like the dots color coded according to sounding data quality & the clickable map it makes it easy to quickly identify the most useful soundings to analyze first, and then I can start checking out some of the yellow ones as needed. Viewing point soundings in AWIPS 2 is cumbersome to put it lightly so the point & click interface is much appreciated. I was also able to look at the all-sky LAP CAPE product for the first time. I really like this product as a "ground truth" for early afternoon CAPE after the morning soundings & to act as a sanity check for RAP/HRRR/etc. forecast soundings. I've used the non-all sky version before in operations & it's really hard to gather much from it with all the data blackouts. The continuity in the all-sky product leads to much easier interpretation & value in operations.

NUCAPS had two "green" sounding locations over the ABQ WFO so I looked at those two first. First thing I noticed was that they were a "little" aggressive when it comes to instability. Below is the NUCAPS sounding from eastern NM.SBCAPE values were close to 4000 J/kg with MLCAPE at least a little bit more realistic at 2270 J/kg. The all-sky CAPE product showed values in the area generally around 1200-1300 J/kg & SPC mesoanalysis had MLCAPE values of 1500-2000 J/kg. Analyzing the NUCAPS sounding the culprit appears to be too high of a sfc dewpoint (59 F vs low 50s F on LAPS) & lapse rates too steep in the mid-levels (850-500 mb of 9.5 C/km). Apparently NUCAPS tends to have a cool & dry bias at the surface so these values are rather surprising to me.

Of course these are the non-corrected soundings so we'll see how the corrected version compare once they arrive. I'm hoping they are closer to reality because I couldn't gain much in operations from the NUCAPS soundings in this case.

Peter Sunday

ProbWind/Radar Data Balance - ABQ

[21:00 UTC] As strong to severe convection continues to progress through the heart of the CWA, the primary cluster of interest is moving through the greater Albuquerque area with high ProbWind values (in excess of 85%) for an extended period of 10-20 minutes. Certainly from this data alone, special attention should be drawn to these cells for their potential to produce strong/damaging winds. This being said, it's important to use this data in tandem with local radar data as, per the example below, the enhanced wind (60+ kts) as sampled by KABX, emerges outside the ProbWind "area of storm."

 Fig 1: ProbWind and KABX 0.5Z at 20:50z.

 Fig 2: ProbWind and KABX 0.5V at 20:50z.

Rosie Red

Simplifying GLM

Great information to use when forecasting, not helpful for the broadcast side.  This info is wonderful, but I'm struggling with how to simplify and explain it on TV or on social media.  This is similar to dual-pol information.  As a broadcaster we don't have time to show that information, but we use it during severe weather events and during major winter storms. This lightning information would be extremely valuable to have during a blizzard or a nor'easter that may produce thundersnow!

Here are the panels I'm using to familiarize myself with the products.

-Penny Gardens