Storms firing in southern Kansas

While not within the OUN WFO, EWP forecasters noticed a storm in southern Kansas developing as observed by the KTLX radar.  The NOAA/CIMSS ProbSevere model probability jumped to 74% at 2158 UTC with strong vertical growth rates and increasing MRMS MESH values (Figure 1).  The probabilities continued to increase and eventually the NWS Wichita office issued a severe thunderstorm warning at 2211 UTC 7 May 2014 (13 minutes after the probabilities increased to 74% (first time above 50%)) and was at 96% when the warning was issued.

Figure 1.  Animation of NOAA/CIMSS ProbSevere, 0.5 degree KTLX reflectivity and NWS warnings valid 2158 - 2112 UTC 7 May 2014.

-Sieglaff

CI providing lead time to initiation

As seen in the first image, CI is picking up on come cloud cover out ahead of the main convection. Probabilities were 50% and higher in this area at the time. Shortly after, thunderstorms began to develop just to the south of the main line that had already been warned on. These new storms later merged with the northern cell to produce more of a cluster. This example shows how the CI tool has some skill at time that cirrus isn’t inhibiting detection and can also raise awareness on development in a messy area.

More warnings and experimental warnings over southwestern Oklahoma

The storms over southwestern Oklahoma have recently increased in intensity and have warranted NWS and EWP severe thunderstorm warnings, with multiple reports of quarter to golf ball sized hail.  The ProbSevere values for these storms with golf ball sized hail are well in excess of 90%--even some at 100% for times.  The evolution of these storms and the generation of severe thunderstorm warnings is demonstrated in Figure 1.

Figure 1.  NOAA/CIMSS ProbSevere, 0.5 degree KTLX reflectivity, and NWS/EWP warnings valid 2132 - 2140 UTC 7 May 2014. 

A question was posed to the forecasters on the KOUN desk within EWP today, "There have been a number of storms with ProbSevere values in excess of 50% today, some of which seem to be false alarms, is this hampering the use of the product?"   The forecasters replied,

"No I like that the storms with the highest ProbSevere probabilities are in excess of 90% and these are the ones producing golf ball sized hail--these are not marginal hail stones.  The ProbSevere is drawing me to which storms are likely to need severe warnings in the near future.  The false alarm storms, while they have high probabilities today, are in the 70-85% range--which makes them different than these with 90+% probabilities.  I've easily been able to adjust to the probabilities and use them appropriately.  Also I know the ProbSevere model has not been validated as a tool to reissue severe warnings, but I like how the probabilities diminish a bit when the radar intensity decreases and then come back up if the storm re-intensifies.  If you look at this display (Figure 3) it has high probabilities on the right storms, but the ones further west are only (correctly )10-20%"

Figure 3.  NOAA/CIMSS ProbSevere and MRMS composite reflectivity valid 2204 UTC 7 May 2014.  This was the display the NWS forecaster in the EWP was referring to when he was discussing the ProbSevere continuing to identify the severe storms, but had much lower probabilities for the storms further north and west.

-Sieglaff

ProbSevere and mature convection

This cell in Laramie Co, WY had a storm report of 1.75″ hail, measured, at 3:51 MDT.

2150Z ProbSevere: 54%, MESH 1.05″

db

2156Z was 18%, .70″

Cluster of high CI values turns into storms

A pronounced cluster of higher CI values evolves into a cluster of convection.

Time stamp 2007Z.

Time stamp 2045Z.

Scott Rudge.

Lightning Jump Detection + ProbWarn

For the first time, we have storms in an LMA domain strong enough to produce images on lightning jump grid.

The four-panel image below contains a 3-sigma lightning jump (top left: orange fill region) the pGLM lightning grid (top right: max flash extent density as high as 18 flashes per min), MRMS reflectivity at -10 C (bottom left), and ProbSevere (94%) overlaid on MRMS MESH (bottom right).

AWIPS2 Screenshot from 2136 UTC on 7 May 2014.

This particular combination has provided a couple ideas for lightning jump algorithm development.  (1) inclusion of metadata similar to the mouse-over ability of the ProbWarn product.  The mouse over for the lightning jump should contain the current flash rate as well as the degree of jump in sigma. (2) Combination with a product similar to ProbWarn (if not, the ProbWarn product itself.  This could provide the forecaster information from satellite,  lightning and radar all-in-one product.  The advantage this provides is that approaches a forecaster-over-the-loop type product without becoming a “black box” as all the information that is part of the product is also provided as metadata.  I look forward to working with CIMSS-WI and other researchers on this type of development.

-K. Calhoun, Week 1 Coordinator and Lightning Jump PI

Texas/Oklahoma Dryline Convection and Satellite Product 4-panel Display

This 4-panel satellite product display provides forecasters with an opportunity to view multiple satellite-based products in conjunction with each other and other observational products. In this particular display, we have transparent nearcast instability field with IR underlayed in the upper left, GOES-R CI and VIS in the upper right, OTD and VIS in the lower left, and NLDN lightning and PGLM total lightning in the lower right.

At 1845 UTC, the NearCast theta-e difference field (instability) had a nose of instability surging from central Texas into central Oklahoma. As a cu field developed within the unstable air, GOES-R CI began to target several cloud objects with probabilities of convective initiation greater than 50%.

By 1935 UTC, several cloud objects with higher probabilities did develop into mature storms within the axis of greatest instability as shown in the NearCast product. Lightning was also being mesaured with this developing convection. Meanwhile, high probabilities of CI, including some >90%, were being detected along the NearCast instability boundary into Oklahoma.

By 2010 UTC, a line of mature convection had developed along the NearCast instability boundary from north Texas into Oklahoma, where CI was detecting relatively high probabilities.

By 2130 UTC, many of these storms were becoming severe, one of which had an overshooting top detected, indicating a particularly strong updraft.

Participants this week have found this 4-panel display to be quite useful, as it helps to reduce the amount of displays they must toggle through. Additionally, many of these products are enhanced when used in conjunction with one another and other observation-based tools.

- Bill Line

possibililty for more severe WY, NE, CO next few hours

Nearcast forecast instability still at its highest across parts of CO, WY, and NE over the next few hours.  Some data gaps here, but the surrounding trend in the data around the gaps lead me to believe there’s still a good road for these storms to travel and hold strength, if not intensify in some areas where daytime heating continues…

Lightning Density/Weak Rotation

The storm that developed earlier this afternoon cycled a few times through its development. At times is showed decent rotation, which was warned on by the Denver WFO. The storm continued to show signs of some possible hail and weak rotation as it crossed the border into Wyoming. The lightning density tool did a good job in picking up on the storm, as show above. Lightning density seems to be a neat tool for awareness, not only for lightning being produced, but also what storms may be the strongest.

More Severe Storms and some ProbSevere False Alarms

More storms continue to fire along and ahead of the dryline over north central Texas and western Oklahoma Wednesday afternoon.  Another storm became severe warned over Baylor and Archer counties in Texas at 2123 UTC (Figure 1).  The NOAA/CIMSS ProbSevere model had high probabilities (> 70%) on this storm for nearly an hour prior to the warning being issued.  The first severe report with this storm was 1.75" (golf ball) hail at 2130 UTC 7 May 2014 in Westover, TX.

Figure 1.  NOAA/CIMSS ProbSevere and MRMS composite reflectivity at 2118 UTC 7 May 2014--notice the latest warnings features a storm with very high ProbSevere values and had high values for nearly an hour preceding the warning.

Further north, many storms over Oklahoma have had high ProbSevere values but have yet to receive severe thunderstorm warnings nor severe reports, contributing the false alarm counts (Figure 2).  These storms have favorable environmental conditions and have exhibited strong satellite growth rates--along with MRMS MESH values around 1.00"--which explains high probabilities.  Discussions with EWP forecasters are ongoing on why these storms do not seem to be producing severe weather.

Figure 2.  NOAA/CIMSS ProbSevere and MRMS composite reflectivity at 2100 UTC 7 May 2014.  Notice many storms over Oklahoma with high ProbSevere values (white and pink contours)--as of this writing these remain as false alarms as no severe reports have been received with these storms.

-Sieglaff