Month: May 2011

Week 3 summary (May 23-27)

Posted in Weekly Summaries on by Travis Smith.

Week #3 had a very interesting local event, with the following guest NWS forecasters:  Jason Jordan (WFO Lubbock, TX), Daniel Leins (WFO Phoenix, AZ), Bobby Prentice (WDTB, Norman, OK), Pablo Santos (WFO Miami, FL), and Kevin E. Smith (WFO Paducah, KY).  Other visiting participants this week will include Chris Jewett (UAH), Scott Rudlosky (UMD), Lee Cronce (UW-CIMSS), and Rudolf (Rudi) Kaltenböck (Austro Control, Vienna, Austria)

Overview of week 3

Monday was primarily a training day, and was spent familiarizing the forecasters with the products.  They examined both the playback case we have used consistently each week of the experiment, as well as some real-time storms that developed in western OK.

Tuesday was possibly one of the more exciting days in the 5-year history of the EWP.  The morning shift focused on examining the OUN WRF and other data sets, producing the discussion “Tornado Outbreak Likely over KS/OK/n TX.”  We met with the EFP for a combined discussion at 1 pm, and quickly regrouped in the Development Lab for a more detailed strategy session, and were into operations mode by 2pm.

Bobby Prentice briefs the joint EWP/EFP (as well as a few media members) prior to the May 24th outbreak event.

As we moved into the mid-afternoon, supercells developed by 3:30pm, and by 4pm there were tornadoes being observed by spotters and shown in real-time on the Situational Awareness Display.

A tornado is observed in real-time on the HWT Situational Awareness Display.

With several supercells approaching central Oklahoma, one group took responsibility for the northern cluster of storms, while the other group observed the southern storms.  Forecasters were able to evaluate all the experimental products (GOES-R, 3DVAR, OUN WRF), although the pGLM feed stopped when one of the OK Lightning Mapping Array sites was damaged by a tornado.  At 5:45pm, the National Weather Center security desk called for everyone to take shelter on the lower level of the NWC.  A few forecasters stayed and observed the storm approaching on radar, but operations were suspended.

As Jason Jordan wrote:

The majority of the forecasters stayed in the HWT to watch the storms as they approached the National Weather Center. Live data from the PAR along with area TDWRs and the KTLX radar showed an impressive evolution of two confirmed tornadic debris balls as the storms moved towards us.

The 3DVar products all handled the track and evolution of the storms very well and the combined radar products also have an excellent track of the tornadoes as well. Continuity was maintained as the storms moved into the cone of silence of the KTLX radar.

As the storms started to move into the metro OKC area, attention to the details/operations was lost as we watched live TV feeds and could see the hail falling outside the WFO window. The excitement rapidly turned to sorrow however as the live TV feeds showed homes and structures being ripped apart.

One last item that made it very clear how close we were to being impacted by the tornadoes directly; leaf and light matter debris was falling from the sky when several EWP members went up to the roof of the NWC to see the dissipation of the tornado moving south of Norman.

Because Central Oklahoma was affected by several violent tornadoes, we suspended operations on Wednesday, and all EWP participants assisted the Norman NWSFO in surveying the damage.  With the help of the EWP teams and others from the Norman community, 8-10 groups of 2-3 people each were able to survey a majority of the damage in one day.

Old Glory flies near Blanchard OK, in the path of an EF4 tornado's destruction.

Thursday’s operations focused on convection in Pennsylvania and Maryland, which allowed additional use of the pGLM products from the DC LMA.  The CI and Nearcast products were examined during the early shift, and the 3DVAR and other remaining satellite products were used during warning operations.

Our usual Friday round-table discussion of the week’s activities provided a lot of additional feedback.  Comments:

UH CI:

  • performance should improve with next-gen satellites.  Probabilities would be a good addition.
  • the CI algorithm may not work work outside the plains region (although it did work in Florida on Thursday)

Other Satellite products:

  • the precipitable water was a nice utility.  Theta-E max on Tuesday showed that the storm was moving into an even more unstable environment.  Gave some additional lead time.  Chris S. commented that this was not the way the creators originally intended to use it, but is a nice fall-out from the research.
  • another forecaster commented that these products could be useful for off-shore significant weather.

pGLM:

  • Tuesday, looking start of El Reno storm, cell mergers, rapid increase in flash rate w/ big changes in updraft intensity.  Downstream increase in anvil activity seemed predictive of where the supercell was moving / regenerating.   We also saw that in the Sterling data on Thursday – rapid increase, led to a closer look and noticed that new cell generation was occurring.
  • 10-15 minute lead time over CG network.   Lots of potential uses, but need more research.
  • General consensus is the a ration of in-cloud to CG-lightning would be interesting.
  • The presence of persistent lightning over time may be related to flash flooding

OUN WRF:

  • it did really well on Tuesday.  Looked at it hour-after-hour.  Updraft Helicity, vorticity.  Probably an accident (jokingly), but was surprised how well it did.  Good groundwork for Warn-on-Forecast.  Very promising.
  • echo previous comment.  Could look at HRRR model for initial conditions.  May be a good boundary condition for OUN WRF in situations where you have less-than-stellar data.
  • Florida forecasters were impressed with HRRR in FL so much that they have started to use it as initial boundary condition.  Have you done any verification versus MR/MS products?
  • OUN would like to use the SPC methods for scoring output for this.
  • the displays are unviewable in some cases.  Too cluttered.
  • Flash Flood – would be nice to have accumulated precip.
  • could do Rotation Tracks, trend analysis.

Side discussion on mesoscale and storm-scale ensembles:

  • need a way to establish reliability of ensembles
  • challenge to consider options – need a statistical complement to the ensemble – statistical distribution of storm behavior.
  • Mark DeMaria paper on blending statistical and dynamic model ensembles to determine improve reliability
  • also reference independent study in the Miami Herald on Probability of Precipitation forecast.  Newspaper used a reliability diagram to show NWS PoP skill.

3DVAR :

  • liked updraft intensity a lot.  Could be used in the microburst environment to detect which cells may be severe.
  • Did an outstanding job on the Tuesday event
  • No doubt that this would be useful.  Need to get it into OSIP right away.

AWIPS thoughts:

  • need some default procedures in AWIPS.  Half the battle was that it was very inefficient to view them.   Lots of time wasted.
  • yes!  Had to recreate his procedures.   Much of his data was missing do to not having a full feed in AWIPS (note: this will be fixed in AWIPS2 next year).
  • most of these are just relational.  Want to evaluate as many procdures as possible in as little time as possible.    Synergistic across multiple projects.

Other forecaster thoughts:

  • Powerpoint training is not the best.  Would prefer “Articulates”
  • include data from previous real-time case to demonstrate.  Perhaps a Virtual Machine for AWIPS
  • forecasters should be required to do pre-work before arriving at the HWT.  This would allow Monday to be used for operations instead of training.

– Travis Smith, weekly coordinator

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pGLM perspective on 23-24 May 2011 Oklahoma storms

Posted in Live Blogs on by Kristin Calhoun.

This week started with two very active days within the OUN CWA which allowed EWP forecasters to incorporate pseudo-GLM products into their warning operations.  Despite the dense radar coverage, forecasters used the total lightning products and provided some interesting insights.

Day One – Monday 23 May

Two storms developed in Northwest Oklahoma and exhibited very different lightning and radar signatures.  The northern storm formed in Major County, exhibited very large IC flash rates, and produced large hail.  Conversely, the flash densities were much smaller in the southern storm which produced a brief tornado.  This observation illustrated the variability between two storms that occurred in a similar environment and emphasizes the importance of continued research on the relationships between lightning and radar within individual storms.

2123 UTC 23 May 2011. 1 min pGLM flash rate and NLDN lightning (top) & KTLX 0.5 deg Reflectivity (bottom)

The greatest pseudo-GLM densities (> 30 flashes min^{-1}) accompanied a large storm cluster which followed the merger of two strong storms.  The 3D-Var products indicated a strong updraft throughout the length of this storm cluster which helps explain the high flash rates.

2216 UTC 21 May 2011. pGLM flash rate, NLDN lightning and KTLX 0.5 deg reflectivity

Day Two – Tuesday 24 May

The high risk forecast and model-derived products all indicated a very active day was in store.  The CI products identified the initial convection 15-20 minutes prior to the first pseudo-GLM signatures.  Flash rates increased rapidly in the earliest convection, and the first tornadic storm occurred as two isolated storms merged near Weatherford, OK.  Flash rates spiked as the two storms merged, coincident with an increase in mid-level rotation.  These combined observations increased forecaster confidence as they issued the first tornado warning of the day.

1951 UTC 24 May 2011. pGLM flash rate (top left), MESH 30 min track (top right), Radar-derived Rotation Tracks (bottom left), and Reflectivity at -20 C (bottom right)

The EWP forecasters observed that the greatest pseudo-GLM flash densities consistently tracked ahead of the main updraft and actually helped to identify changes in storm motion.  On several occasions the pseudo-GLM densities also indicated that the main center of rotation was shifting prior to the identification of new rotation tracks by the multi-radar multi-sensor algorithms.

2009 UTC 24 May 2011. pGLM max flash rates, 60 min track (top left), 30 min max MESH track (top right), 30 min Rotation Tracks (bottom left), Reflectivity at -20 C (bottom right).

Although lightning jumps preceded many of the tornados, forecasters commented that they would have liked to examine time trends for individual storms.  This has been a common theme during previous spring experiments, and was not fully accounted for by plotting swaths of the pseudo-GLM products.

2123 UTC 24 May 2011. 60 min track pGLM flash rate, 30 min MESH track, 30 min Rotation Track, Reflectivity at -20 C

-Scott Rudlosky (pGLM scientist week 3)

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pGLM products in the mid-Atlantic 26 May 2011

Posted in Live Blogs on by Kristin Calhoun.

Forecasters conducted warning operations in the Sterling, VA and State College, PA CWAs, which allowed for analysis of the pseudo-GLM products (from the DCLMA). Although the earliest convection initiated along and just west of the Appalachian Mountains (out of range of the LMA), storms soon formed within range. Isolated storms initiated and developed rapidly ahead of the main line. The pseudo-GLM products detected IC flashes ~10 min prior to the first CG flashes in two of these storms. These storms continued to intensify and eventually merged into a line, further increasing the flash rates.

2116 UTC 26 May 2011. pGLM flash rate and NLDN lightning, low-level vorticity track (3D-Var), 60 min max MESH track, reflectivity at -10 C.

As the discrete cells merged into a line, flashes remained frequent, and the pseudo-GLM products helped confirm the strength of individual cells within the line. Greater flash rates also helped identify areas of new convection as they formed along the line.

2317 UTC 26 May 2011. pGLM flash rate (bright) and 60 min Max Track (shadowed), reflectivity at -10 C, 60 min max MESH trackk, 60 min updraft track from 3D-Var.

Forecasters also observed that the pseudo-GLM swaths (i.e., 60 min sum of flashes) helped to illustrate persistent cells and identify the most intense portions of the line.

2336 UTC 26 May 2011. 60 min sum of pGLM flashrate, 120 Updraft track from 3D-Var analysis, 120 min Low-level (<3km) Vorticity track, 60 min MESH maximum track

The above screen captures illustrate several four panel displays used to compare individual products in AWIPS. The pseudo-GLM products often were plotted alongside the 3-D Var updraft and vorticity tracks, as well as the multi-radar multi-sensor hail swaths and reflectivity at -10 C.

Scott Rudlosky (pGLM scientist, week 3)

Tags: None

20110526 EWP Operational Morning Discussion

Posted in Live Blogs on by Kevin Manross.

Previous forecast remains on track.  We have decided to begin at Sterling so we can interrogate lighting products even thought we think this will be at the southern end of the best severe storm area.

Mostly sunny skies in combination with relatively steep mid-level lapse rates have led to extremely unstable air with CAPE values in the 3-4K range over VT-NY-ern PA-wrn MD-N VA area with CIN removed.  A shortwave trough, perhaps convectively reinforced, was located over srn OH-ern KY moving east.  Effective shear values are increasing rapidly.

CI has already occured over ern WV.  We are in luck.

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That was a close call!

Posted in Live Blogs on by Travis Smith.

The majority of the forecasters stayed in the HWT to watch the storms as they approached the National Weather Center. Live data from the PAR along with area TDWRs and the KTLX radar showed an impressive evolution of two confirmed tornadic debris balls as the storms moved towards us.

The 3DVar products all handled the track and evolution of the storms very well and the combined radar products also have an excellent track of the tornadoes as well. Continuity was maintained as the storms moved into the cone of silence of the KTLX radar.

As the storms started to move into the metro OKC area, attention to the details/operations was lost as we watched live TV feeds and could see the hail falling outside the WFO window. The excitement rapidly turned to sorrow however as the live TV feeds showed homes and structures being ripped apart.

One last item that made it very clear how close we were to being impacted by the tornadoes directly; leaf and light matter debris was falling from the sky when several EWP members went up to the roof of the NWC to see the dissipation of the tornado moving south of Norman.

Back to operations…

-Jason Jordan

Tags: None
Posted in Live Blogs on by Travis Smith.

Pablo is issuing a SVR for storms near Byers and Ryan tracking northeast at 55mph. Nice MESH tracks on both of them. Ryan storm appears to be a left split. Too close together to write two boxes.