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General Information and News
We have begun EWP 2011 Week 2. With us this week are:
Kevin Brown (OUN), Kevin Donofrio (PQR), Bill Goodman (OKX), Steve Keighton (RNK), Jessica Schultz (ROC)
We will be going through training fore most of the day ending with the 19 May 2010 DRT case.
-K Manross: Week 2 EWP Weekly Coordinator
Today’s afternoon shift started with forecasters working across the Norman, Tulsa, and Little Rock county warning areas. With the some storms beginning to form south and east of Norman, Oklahoma, it was felt this would be a good opportunity to take another look at the PGLM flash extent density observations and focus on total lightning. The PGLM flash extent density was very useful in identifying when the first cloud-to-ground strikes would occur. The PGLM was preceeding the first cloud-to-ground strike by approximately 30 minutes today.
As the the afternoon progressed, the storms began to intensify, both on radar and with the PGLM flash extent density and we shifted from using the PGLM for lightning safety and moved into warning operations. By 2211 UTC on 12 May 2011 (the first image of the loop shown above), three severe thunderstorm warnings were in effect. The area of interest for this post is in between the two existing warnings in the west. At 2211, the PGLM flash extent density was no more than a few flashes per minute. By 2214 UTC the number of PGLM flashes was already approaching 40 per minute. This continued to rapidly increase through 2220 UTC when the PGLM flash extent density observe 82 flashes in a 1 minute interval for a single 8×8 km grid box. This was one of the largest lightning jumps of the day with an increase of 75 flashes per minute in a nine minute time span. With this major lightning jump, along with the forecaster’s interrogation of radar data, a new severe thunderstorm warning was issued at 2226 UTC. This warning was later verified with several severe hail reports.
Submitted by Geoffrey Stano, PGLM PI for week of 9-13 May.
CI is occurring within area of MLCAPE aoa 2000 J/kg along cold front extending from just east of KBVO to just north of KADM. Cells initally were discreet but have been merging/growing into short multicell segments. Additional isold convection is developing within broad warm sector over northeastern TX northeast into Pushmataha and LeFlore counties. Multicellular convection in this area looks enfeebled both visually and on radar. Weak low and mid level SR flow indicates an evolution into a linear mode. Given the amount of instability present along with mid tropospheric jet streak approaching area expect hail to 2 cm and wind gusts to 30 m/s.
Previous forecast had CI in a broad zone extending from near KJLN south to KMEZ. Mesoanalysis showed a persistent area of lower CAPE in this region, owing to increased cloudiness and inhibited insolation. Convection in this area appears shallow and unelectrified.
19Z run of the oun-wrf overconvected over southeastern OK and did not represent reality. The 20z run, however, is sampling the CI and hopefully will provide a better solution.
Blair/Curran
We’ve moved straight to storm analysis and warning ops this afternoon. Forecasters Blair/Curran/Vincent are monitoring Tulsa’s CWA, Taylor in Little Rock CWA and Billings just quickly moved over to OUN to monitor the storms producing lightning in the southern end of the domain.
Initial thoughts focus on the Tulsa (TSA) as well as the Springfield (SGF) and Little Rock (LZK) CWAs for convective initiation and storm maturity. Latest visible satellite imagery depicts congested cumulus field over southeast Oklahoma in response to continued low-level moisture transport and broad ascent with analyzed speed maximum across northeast Texas.
Main severe weather threats will likely be large hail up to golfball size and damaging winds in excess of 60 mph with well-organized multicell storms or a few supercells. Tornado threat appears low today with marginal low-level shear within the 0-1 km layer. However, any unresolved storm-scale boundaries from early morning convection within the warm sector of far eastern Oklahoma or western Arkansas may locally enhance isolated tornado threat.
Blair/Curren
Today was an active day for our visiting forecasters, but not in the way we were originally expecting at the end of the previous shift with models initially forecasting development of supercells along the dryline in central and western Oklahoma. As the CI forecasters began their morning forecast, it was already evident that the ongoing convection in western Oklahoma had greatly modified the forecast from the day before. Initially, none of the high-resolution models had a handle on the overnight convection, but the OUN-WRF and HRRR were beginning to modify with each successive run, keying in on the development of MCS moving across Oklahoma and the possibility of rotating storms further north near the CO/KS border associated with the closed Low.
The split of forecasters between these two regions seemed to work out well. Forecasters focusing on the Oklahoma region were able to examine both the pGLM over the Oklahoma LMA network and 3D-VAR data as the MCS reached its peak strength. Meanwhile, GLD and DDC forecasters monitored CI and later were able to incorporate 3D-VAR data in their analysis as things wound down in central Oklahoma and we moved to the floater domain. While none of these storms produced tornadoes, the vorticity product from the 3D-VAR was easily incorporated into the analyses and seemed to prove useful in the warning decision process.
-K. Kuhlman (weekly coordinator)
Brian and Scott have been watching a storm in E Colorado that produced hail and wind damage. They commented that the 3DVAR analysis seems to produce a very realistic wind field at the 1.5 km level for the storm of interest.
As we watched the storms move through central Oklahoma today a small, isolated cell developed over Lawton, Oklahoma. This storm conveniently gave us the opportunity to show the effectiveness of total lightning observations in helping gain lead-time ahead of the first cloud-to-ground lightning strike. This small cell turned out to be even more interesting as the PGLM observations gave a 29 minute lead-time over the first cloud-to-ground strike. This was pretty remarkable as the lead time is usually on the order of 5-10 minutes. Below are three images showing the event.
-Geoffrey Stano (NASA/SPORT)
Central Oklahoma had several strong thunderstorms move through the region and the forecasters at the Spring Program had the chance to check out the pseudo geostationary lightning products derived from the Oklahoma lightning mapping array. Most of our time was spent investigating the products and discussing the various pros and cons. The figure above shows a good use for these data in a lightning safety perspective. The 1-minute PGLM flash extent density (and the corresponding NLDN cloud-to-ground lightning data) are tightly clustered with the the stronger convective regions, indicated by strong radar reflectivity. However, unlike the NLDN data, the PGLM flash extent density still showed that lightning flashes were extended anywhere from 8-32 km into the stratiform region. This shows the advantage of seeing the spatial extent of lightning activity available from total lightning observations. This is further emphasized with the PGLM maximum flash density in the upper-right which shows the maximum PGLM for each grid box for the past 60 minutes. This shows that most of central Oklahoma has had lightning activity within the past hour, indicating that the threat of a cloud-to-ground strike still exists.
-Geoffrey Stano (PGLM Principal Investigator)
Brandon has been comparing the 3DVAR data with the regional radars across OUN, specifically max vorticity from 3DVAR vs radial velocity data.
Below is a screenshot from 2111 UTC including max vorticity of about 0.01 s^-2 to storm relative velocity (at 1.8, 2.4, and 3.1 degrees elevation) from KTLX:
-K. Kuhlman
