KDDC: SVR Use of Prob Severe In Warning Decision

Issued a severe thunderstorm warning as 50 dBZ was reaching 35,000 feet and there was a significant storm top divergence signature aloft. A three body scatter spike was also seen. Prob Severe values for hail increased to over 90% and then have been consistently around 98% since warning issuance.

See blog post called Prob Severe compared to Classic Radar Interrogation Techniques

An LSR for hail of hen egg size (2.00 inches) came in 2 minutes after the warning was issued.

At 3:21 pm, a report of ping pong ball sized hail (1.50 inches) was reported.

I was having an issue with the text workstation, which delayed the issuance by a few minutes.


Issued a new severe thunderstorm warning on the same storm as Prob Severe has consistently been running over 90% for hail and has even shown an increase in Prob Wind which is now 80%. 60 dBZ was also reaching 35,000 feet which is well above the -20C (~22,000ft).

Several reports have also come in since the time of new issuance of warning including hail half-dollar to the size of golf balls, which the MESH was indicating as well.

The storm briefly weakened before similiar signals were indicated in all tilts with 60 dBZ reaching ober 30,000 feet and a consistently high Prob Severe value at 98%.

-Ironman

GLM data vs Earth Networks in Prob Severe

A strengthening storm over the NW part of DDC area had big increase in CG lightning activity, but there was very little shown in the GLM data. See image below.

GLM data continued to be much lower and insignificant whereas the CG data was showing about 50 flashes per minute. This storm had about 60 dBZ over 20,000 feet, so higher cloud flashes would be expected, but its not being shown.

GLM vs. NLDN

GLM showed important utility by providing lead time for eventual cloud-to-ground lightning.

At 1850 UTC, GLM indicated the presence of flashes (and associated events):

 This quantity of events and flashes increased by 1920 UTC:

By this time (20 minutes later), the first cloud-to-ground strikes were detected by NLDN:

-Lost Met

Chicago: Meso-Analysis

Meso Analysis: Chicago (LOT):

Main points up front:

• GOES 16 derived stability indicies help diagnosis the anemic convective development in LOT's CWA. 
• GOES 16 derived stability helped reveal areas where convection is most likley to become active later (western CWA).
• Metop-A Nucaps passes added confidence to the analysis seen in GOES-16.

Initial line of convection and outflow boundary struggling to sustain deep convection across the northern CWA and little new convection firing along the outflow boundary as seen by the radar above. 

The GOES-16 Derived Products:

GOES-16 derived stability fields show helpful information of weak CAPE values of only a few hundred (J/kg) and positive LI's across much of the LOT CWA.

 

An analysis about 45 minutes layer and using a compressed color scale to increase contrast shows the most favorable activity would be along the western CWA which showed higher CAPE (300-400 j/kg), negative LI's, and few tenth's higher on PWs. This matches well with surface observations which show higher surface temps and dewpoints in the mid-50s to lower 60s in Davenports area. 

Metop-A NUCAPS & GOES-16 Airmas RGB:

Overlaid Airmas RGB and Metop-A pass to compare. No strong signal evident of moisture or large dry layers intruding into the areas. Did sample and modify Metop-A dervide soundings in the Davenport sounding to the west and more stable environment to the east. Overall, modified soundings show a similar pattern of slightly more unstable to the west where convection is initially firing. 

Forecaster: Tahoe

Met-Op Sounding

A met-op pass occurred around 17z over the DDC region. The surface temperature of the sounding was consistent with actual observations in the area. I did have to modify the surface dew point as the sounding had 62F and the surface obs were closer to 68F. The modified sounding is below, which showed about 4,500 J/Kg of SBCAPE.

This value is more consistent with data in SPC mesoanalyis, whereas the original sounding showed only about 2,000 J/KG of SBCAPE.

-Ironman

VIS/IR Sandwich Procedure

The "Sandwich"  combo is very useful for situational awareness and developing convection. When the first developing cell intensified, colder cloud tops were clearly shown in the IR, with the cu field with less vertical depth clearly identifiable with weaker cells.

-Ironman

4-Panel Baseline Derived Products

A useful 4-panel for mesoscale analysis using Baseline Derived Products is to have TPW, CAPE, and LI with the Moisture Difference product. This gave me a quick look at the changing environment with increasing moisture and instability. The moisture difference product adds value due to its higher resolution. Once the product was explained in more details, it makes sense why areas with thicker cloud appear darker. This could be confusing at first glance since drier areas are darker.

-Ironman

IR/Visible Sandwich

A procedure that combined both visible and IR GOES-16 data provided excellent situational awareness for initiating convection. The "sandwich" display has visible with semi-transparent IR overlay.

In the example below, the appearance of cooling cloud tops gave a heads up that deep, moist convection was initiating:

-Lost Met

EWP Week 1 Day 2 Operations

On day two of the 2017 experiment, our two groups are operating in the DOdge City, KS and Chicago, IL CWA's.

EWP Week 1 Day 1 Summary

During the first day of the 2017 GOES-R/JPSS Spring Experiment, our two pairs of forecasters operated in the Boston and Raleigh CWA's.

-Bill Line, NWS

• GOES-16 ABI Imagery and products
• Imagery
• Seeing cooling tops in the IR combined with structure of cu development in the VIS (sandwich product) with 1-min resolution keyed my eyes to development along a line before anything else.
• Used imagery mostly for identifying cloud top warming of storms. We did not warn on storms that had warming tops. The storms we did warn on had OTs
• We identified weak/weakening storms from warming tops, or uniform on vis
• Initial convection could be seen going up much sooner in satellite than on radar
• Nice to have 1-min 2-panel IR and VIS on the side next to my radar/warning display. It provides a  very clean, situational awareness display
• Would be nice to time synch 2 panel with single panel on the side
• Derived products (winds, dsi, tpw)
• Winds did not look well. Color coding by wind speed was not helpful.  Color coding by height or pressure level would be better. Barb tells you the wind speed already, no color coding needed. Also many of the winds were completely wrong in speed and direction. Compared with obs (surface winds). Few vectors, very limited.
• Dsi and tpw - There were many holes in the baseline TPW and CAPE, making it difficult to interpret. If too many holes, I will look at other tools.
• Using GFS as a first guess is not ideal. It would be better to have a separate CONUS sector using RAP or HRRR as the first guess, something that updates with new sfc obs every hour.
• Channel differences
• RGB composites
• GLM
• This is the first time we’ve seen GLM data. The lightning placement is a bit off geographically compared to radar. Flashes seem most intuitive, similar to what we are used to seeing from NLDN. I want to know when I would use GLM instead of NLDN? As for gridded events, not sure how I’d use it for warning ops. Color tables worked fine for me.
• I liked the gridded color scale you put together. I like just a simple scale. Brighter colors focus my eyes.
• I didn't notice anything that was too off. With pulse convection, you could see convection pop up quick, and then flatten out quick. Confidence that stuff wasn't going to keep strengthening early on because not really any rapid lightning increases
• ProbSevere
• In our case it wasn't working  too good today.  For a storm that had high velocity in radar, probs were too low because not much azimuthal shear. Spurious data in azimuthal shear product can also cause bad ProbSevere probs.
• Pulse nature of what we were seeing was highlighted in probsevere. Seeing probsevere probs pulsing verified the environment we were in. So it was useful in this sense.
• Used it more for confidence building and not as much warning decision.
• NUCAPS
• Experimental modified nucaps came in very late. But comparisons showed that modification did improve thermodynamic values.
• Operational pass was a little late to be helpful. 1.5 hr to 2 hour after timestamp.
• Experimental data with modified sounding was better than the one that wasn’t. CAPE was closer to that on mesoanlaysis and helped to verify environment we were in.