KDDC: SVR issuance based on Prob Severe

The cell in the middle of the image rapidly intensified with Prob Severe of 95% for hail and a MESH of 2.50 inches. Based on this alone I had enough confidence to issue a new warning with the environment and previous storm in the same region.

 At 4:32pm, right when the warning was issued, a report of 2.5" inch all was reported.

These storms today in the NW DDC area have been producing large hail, and the Prob Hail model within Prob Severe has been very consistent with what has been observed, and giving confidence in issuance of other experimental severe thunderstorm warnings in the region.

Testbed observations yields ProbSevere training point

The post about a severe wind gust in the Chicago WFO (http://goesrhwt.blogspot.com/2017/06/prob-severe-severe-outflow-wind-report.html) offers insight on a subtle, yet important point that should be communicated to ProbSevere users in the training module.  In this example, a storm produced strong outflow winds that raised away from the reflectivity core far enough such that it no longer was encompassed by the ProbSevere object.  As a result, the ProbSevere (ProbWind) probability was 0%.  For storms were outflow is expected to race away from the reflectivity core, users should be aware the ProbWind model may underestimate (possibly by a large amount) the probability of severe winds.  Additionally, this is another example of where maximum velocity magnitude could be a very useful observation for the automated prediction/detection of severe winds.

-Sieglaff

Severe hail from storm in Dodge City WFO

A severe thunderstorm had developed over the northwestern Dodge City, Kansas CWA Tuesday afternoon.  The NOAA/CIMSS ProbSevere values cycled between 45 and roughly 70% from 1925 until 1952 UTC; then radar observed reflectivity core rapidly increased, causing the ProbSevere values to correspondingly jump from 71% at 1952 UTC to 94% at 1956 UTC.  The jump in ProbSevere values as well as other features on radar (very strong storm top divergence and 3-body scatter spike (see post: http://goesrhwt.blogspot.com/2017/06/probsevere-compared-to-classic-radar.html)) warranted the DDC team to issue an experimental severe thunderstorm warning.  Shortly after the warning, 2.00" hail reports were received.

Figure 1. KDDC 0.5 degree reflectivity and ProbSevere contours valid 1926 - 1958 UTC 20 June 2017 for select times.

Another valuable discussion between myself and the forecaster was had where we examined the storm top divergence with this storm.  Strong storm-top divergence is something that often precedes a rapid intensification of a thunderstorm (and often severe reports).  Storm-top divergence is something a forecaster can quickly identify by analyzing all-tilts of base velocity data, but an automated storm-top divergence field is unavailable from the MRMS suite of products.  Such a field being made available in the MRMS suite could would be valuable for evaluation and possible inclusion into the ProbSevere model.

-Sieglaff

Prob-Severe: Severe outflow wind report.

Prob-Severe: Severe outflow wind report.

Main Points:

• Spotter reported outflow wind of 67 mph with a cell 1957z.
• ProbSevere showed probabilities of 0% throughout its track.  
• GLM data (not shown) had an increase in activity but nothing that seemed significant compared to earlier in the day. Nothing eye-catching that is. Also, this storm did not produce subsequent CG strikes. 
• Radar radial velocity was the only key piece of information that would allow you to issue a warning on this cell.

Cell of interest was starting to be tracked by Prob Severe about 18:26z through 19:57z. During this time frame ProbSevere kept probabilities at 0% for all elements.  At about 19:40z, an outflow became evident on radial velocity with two maximum of about 45 to 50 dBz (below). The northern max would go on to produce a spotter report of 67mph with tree branches down.

At 1957z (below) the time of the spotter report, the radial velocity displayed an outbound velocity of about 60 knots, while the max was still displaced to the south from the ProbSevere boundary which still showed 0% probs. --Tahoe

Visible Texuture + IR Cloud Top Temps

Another benefit of the GOES-16 "sandwich" procedure (which is visible with a semi-transparent IR overlay) is the ability to see texture associated with the visible imagery while seeing the cloud top temperature.

In this example, the cooling cloud tops are seen by the brighter red in conjunction with the overshooting top in the visible imagery:

-Lost Met

ProbSevere Compared to Classic Radar Integration Techniques

It might be beneficial if ProbSevere included some form of storm-top divergence in its algorithm.

For example, on this 1946 UTC scan, there was ~150 knots of storm-top divergence at ~40,000 ft AGL:

This indicates the presence of an intense updraft, which suggests the storm should continue to intensify and is probably about to produce severe weather.

ProbSevere did show intensification with a gradual increase in percentages (47% to 94%) between 1946 and 1956 UTC:

Nevertheless, incorporating storm-top divergence may help increase the percentages faster.

-Lost Met

NUCAPS Gridded Elevated Lapse Rates...

Hello from the Hazardous Weather Testbed in Norman, OK!

So, we were taking a closer look at the NUCAPS (NOAA Unique Combined Atmospheric Processing System) data, both in the sounding and in the gridded format for severe weather applications.  Today, we are specifically focusing on the potential for deep/severe convection in northern Illinois and western Kansas...and surrounding areas.  It's important to note here that NUCAPS soundings are satellite derived (Soumi NPP, Metop-A, Metop-B and JPSS (future)) and independent of model data.  The NUCAPS soundings have been utilized in the HWT now for three years.  The NUCAPS gridded data meanwhile are a relative new-comer to the HWT, having been implemented briefly at the end of last year's HWT...but are more of a formal product being evaluated this year.  The efforts to get the gridded NUCAPS data into AWIPS were led by the SPoRT group at NASA MSFC and have played a role in weather forecasting in Alaska, especially for the Anchorage CWSU.  Now, we are taking a closer look at the data for potential severe weather applications and trying to think of proper data displays and visualizations.  One thought that came to mind was looking at lapse rates of the NUCAPS vs various model output.  This image shows 700-500 mb lapse rates for the NUCAPS gridded data along with GOES-16 0.64 um imagery (upper left), HRRR (upper right), GFS20 (lower left) and NAM 40 (lower right).

Notice that the 700-500 mb lapse rates from the NUCAPS data are very similar in pattern to the various model data shown above. While specific values at various locations differ by relatively small percentages, patterns and gradients are overall fairly similar.  However, the NUCAPS data suggests perhaps slightly steeper lapse rates (C/km) over portions of the Great Lakes than the suite of model data.  In the environment in that area today, these levels correspond to temperature values roughly in the 0C to -20C temperature range...per NUCAPS soundings.  So, we would expect to see perhaps slightly more robust convective development in this region today, than model data alone might imply.

Next, we're going to take a closer look at some of the NUCAPS soundings in context of both the gridded data and other analysis data sets.

-Kris W and Nadia S

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