Reasons for the slow warns.

Just wanted to add that on some of these storms I have been a little slower on the draw to warn. This is due to examining other new products such as LAPs CAPE and composite reflectivity MESH, while also participating in a round table discussion with some extra students on why and how they impact the mesoscale forecast, how newer dual pol products interact with the old legacy products, and examining the new prob of severe function that surrounds these storms.

MESH seems to be doing excellent here. However MESH and Prob of SVR do not capture  information of the latest lowest scan because the volume is not complete yet. It is important to use Prob of Svr as a trend tool and seeing a quick graph of Prob of Svr rising would be very helpful.  (Again a tie in to SCAN for ease of graphing would be wonderful. )

Grant H.

Thunderstorm Development in Illinois

As mentioned in the previous post on CI, the CI product missed a bulk of the convection that developed along the boundary in Iowa due to the full disk scan. However, subsequent convection developed to the east of those initial thunderstorms in Illinois towards Lake Michigan. The higher probabilities (>70, some up to 92) developed into storms which developed further even in the cold waters of the lake. The forecasters who were in Cheyenne were moved post convective development, but the product was pointed out to them to show how the product performed.

GOES-R CI product at 2200 UTC

GOES-R CI product at 2215 UTC

Same Storm Different Lightning Jump

A secondary lightning jump occurs at 23:28 UTC with the same storm east of Denver Co. The lightning jump here reached the 2 sigma level when the total flash rate increased from 8 flashes per minute to 16 flashes per minute in the span of two minutes. This reinforcing lightning jump indicates that the storm’s updraft was still undergoing periods of intensification.  Baseball size hail was being reported at the time of the jump, and ping pong ball size hail was reported at 23:35 UTC in association with this storm.  Hail was reported as deep as 3 inches on the ground.

*There appears to be a delay between the jump occurrence in the Flash Initiation Density (23:28 UTC) and the LJA sigma plot (23:33 UTC).

Same Storm Different Lightning Jump

A secondary lightning jump occurs at 23:28 UTC with the same storm east of Denver Co. The lightning jump here reached the 2 sigma level when the total flash rate increased from 8 flashes per minute to 16 flashes per minute in the span of two minutes. This reinforcing lightning jump indicates that the storm’s updraft was still undergoing periods of intensification.  Baseball size hail was being reported at the time of the jump, and ping pong ball size hail was reported at 23:35 UTC in association with this storm.  Hail was reported as deep as 3 inches on the ground.

*There appears to be a delay between the jump occurrence in the Flash Initiation Density (23:28 UTC) and the LJA sigma plot (23:33 UTC).

Posted in General, Lightning Jump Algorithm | Leave a reply

Simulated Satellite Imagery Very Useful Today

I decided to look back at the NSSL-WRF Simulated Satellite Imagery (top left) and it is pretty close to the actual IR satellite (top right).  You can also see the MRMS radar (bottom left) that it had the idea of a cluster of storms breaking out in central Iowa to N. Illinois.  The only issue I would say is it may have been slightly slower (30 min-1hr) with initializing the convection.  Other than that it has it timed pretty well after. I like it! ~Vollmar

Simulated Water Vapor Speed Max

Analysis of the simulated water vapor imagery compared to the actual water vapor imagery at 13Z indicated the simulated model had a good handle on the speed max that was located over western KS at 12Z. Although the simulated water vapor/IR was to agressive on TSRAs over western NEb at 13Z this leads to confidence in the position of the speed max later in the day on the simulated water vapor.

-JB

PGLM, Lightning Jump, and Quarter size hail

Example lightning jumps from just east of Denver CO at 2251 UTC. The image above shows the lightning jump feature (shaded purple), flash initiation density (FID; pink boxes) and the meteogram output information.  The top two panels are the sigma levels at which lightning jump occurs, and the bottom panel is the total flash rate from the PGLM.   The Tracking meteogram outline is the white circles encompassing the storm.  Two lightning jumps occur at 2249 and 2251 UTC.  The first jump occurs as the total flash rate from the PGLM reaches 10 flashes per minute (4 sigma level; anything above 2 sigma indicates a lightning jump according to Schultz et al. 2011), and the second jump occurs with the larger increase in total lightning from 5 flashes a minute to 15 flashes per minute (6 sigma).  The jumps are indicating increases in updraft strength and volume,and can be used as a metric in storm intensification.  Quarter size hail was reported approximately 20 minutes later at 2310 UTC.

*note the flash rates are likely higher with this storm because the LMA used in this case only had 5-8 sensors active at any given time.*

Jump in Prob Severe

We have now switched CWA to LOT and have loaded in the MRMS composite reflectivity overlaid with ProbSVR. It is interesting to compare this area to what we were seeing to the west. In eastern WY the probabilities were lower despite rotation on velocity products and supportive 3-dementional reflectivity of a BWER. For the LOT CWA there is very high probabilities.

-JB

Prob. Severe Model and Dual-Pol

The prob. severe model has been a great way to grab attention to storms that need to be monitored for the developing convection over the northern DVN CWA. Taking a look at how well it verified with dual-pol products and spotter reports, this screen capture (below) shows the prob. severe model overlaid on ZDR (upper right) and then 0.5 base reflectivity in the upper left, KDP on the lower left, and CC on the lower right. Based on the severe prob (shows 94% at 2138Z), my partner issued a Severe Thunderstorm Warning ten minutes prior to this screen capture as the probability trend was increasing over time. Having the ability to look at the parameters detailing more specifics about what the model is analyzing is very helpful in maintaining awareness with a particular storm. The MUCAPE (2325 J/kg, shown) and effective bulk shear (50.3 kts., also shown) being consolidated into one quick click of a mouse is much faster and easier than going to pull up the RAP elsewhere and analyzing the local storm environment. One other parameter that might be helpful is effective SRH. As for the other current, existing parameters, the same could be said as the other two above: the MRMS MESH, while overdone, provides an opportunity to monitor trends; and the satellite progs with annotations indicating whether or not the vertical growth rate and glaciation rate is moderate, strong, etc. is helpful and allows for increased confidence when utilizing this tool with other, more traditional methods. Without knowing how the exact values with respect to the satellite-tracking rates translate to growth/decay, the annotations deciphering what the values mean is critical to understanding the storm’s trend.

Comparing the prob. severe outline with the storm in question, dual-pol showed KDP values that were blacked out (with surrounding pixels well above 1), CC values below 1 (~.8 to .9), and a small but still evident three-body scatter spike. DVN received a report on this storm just two minutes later that was close to severe criteria:

LSRDVN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
445 PM CDT TUE MAY 20 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0440 PM     HAIL             2 W DUBUQUE REGIONAL AI 42.40N 90.75W
05/20/2014  M0.88 INCH       DUBUQUE            IA   EMERGENCY MNGR

            PEA TO NICKEL SIZE HAIL REPORTED ON HIGHWAY 151.

&&
Ten minutes later, another report of hail over severe criteria was issued from DVN, verifying my partner’s warning, the prob. severe model, and what was seen in radar trends:

LSRDVN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
457 PM CDT TUE MAY 20 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0450 PM     HAIL             1 E DUBUQUE REGIONAL AI 42.40N 90.70W
05/20/2014  M1.50 INCH       DUBUQUE            IA   EMERGENCY MNGR

&&
Overall and so far, this tool is a great resource and would be good to have in the toolbox.

~Linda

Using Probability of Severe to help issue Warnings

It has been a very active day with storms over our warning area.  The Prob. of Severe tool really helped me focus in on the storms that were more intense and then I was able to use Dual-Pol info to help verify and issue the warnings.  I was able to observe that the Prob of Severe as it followed the strengthening and thus weakening of the individual storms.  As you can see from above…when they turned the hot pink color..is normally when I was issuing the warning and actually allowed the warnings to expire when they started to drop down to the gray color.  This also verified with storm spotter data so I find this tool very useful and I really like it. ~Vollmar