CI/CTC Identifying Developing Convection in a Favorable Environment

The western sections of the San Angelo TX CWA have become quite favorable for thunderstorm development. First, here is a look at the sounding from nearby Midland TX at 12Z.

MAF 12Z Sounding

The values seen here are confirmed by RAP13 (pictured) and OUNWRF soundings just ahead of the developing convection near San Antonio.

RAP13 Sounding nearing San Angelo at 19Z

Lapse rates are extremely steep, and the moisture quality is quite good as well. Deep layer shear is favorable for supercells.

The LAPS 1km (OUN domain) data showed that the dryline in this area would activate explosively, in an area with 3000 J/KG CAPE (first image, top right corner) and LI values near -10 C (first image, bottom left corner). The second image is after the storms are mature, so these values diminish with time due to the convection (perhaps too aggressively ahead of the convection).

1KM LAPS Convective Forecast at 1830Z.

1KM LAPS Convective Forecast at 1930Z.

Because this is an area of clearing behind the large cirrus shield associated with the central Texas MCS, the GOES products are providing information about development in this region.

GOES CI/CTC at 1830Z. Note the areas of enhanced values near the dryline.

GOES CI/CTC at 1845Z. Note the areas of enhanced values near the dryline.

A warning was issued based on this data. The polygon was massaged to incorporate both aggressive CI signal to the south and CTC signal to the north. The UAH CI product was persistent in depicting 90 plus percent probabilities of CI while the CTC product indicated 10 to 15 degrees of cooling over a 15 minute interval. No reports were received to verify the warning, but MESH did end up indicating values of 0.87 inches, which has correlated to severe hail in past events and similar environments this week.

–Hatzos/Guseman

CTC Error Off the Charts

The Cloud-top-Cooling algorithm was off the charts with values of -60 C/15min. This is most likely due to some error in the computing as the anvil moved east. The previous IR frame had no thunderstorm cloud over the location and the cloud top temperature went from +12 to -41 C. This could be a one time error, as other frames do not show this, but something a forecaster needs to be aware of.

Hampshire

Daily Debriefing 5/9/13

Yesterday evening (2-10pm) turned out to be a busy shift, our focus on the OUN and LUB CWAs. Multiple warnings were issued and a lot of good feedback was collected. We even got a bonus and were able to watch a storm roll right overhead from the NWC's observation deck!

Really neat lightning (and hail) show aside, here's some of the forecaster comments from our shift:

Cloud Top Cooling
- 'There was a signal early that rapidly cooled to -26C and I did issue a warning off of that.'
- 'Because of the jet streak moving through central Texas and then the cirrus blowoff from the development of various convective cells, the product struggled due to the cloud contamination.'
- 'Radar can't look through mountains... in the same manner, satellite can't look through clouds.' ...from a product PI

GOES-R CI
- The GOES-R CI had the same struggle at the the CTC. Because of the cirrus contamination forecasters weren't able to utilize it aside from a few cells early on.

PGLM and associated lighting applications
- 'There were some pretty impressive lightning jumps in storms that eventually produced strong winds.'
- 'The lightning jumps did seem to be associated with storm top divergence, storm top growth... so there was a jump on the strengthening of the updraft and the storm itself.'
- 'I liked the idea of the tracking tool, but it was difficult to use with the storms that were barely moving.   It became a very labor intensive task.'
- Forecasters also noted that the number of strikes in the OKLMA network were fewer than anticipated for the strength of the storms. However, after some exploration it was discovered that not all of the LMA sensors were functional and this limited the amount of flashes detected.

Today's focus area will be slightly further south, covering San Angelo and Fort Worth, TX with possible coverage of OUN later in the afternoon. Cloud cover is already widespread over a broad area in this region, but we are hopeful for some clearing and development on the back end where the GOES-R CI and the CTC can be utilized again.

Evaluating the Total Lightning Tracking Tool

Posted by Geoffrey Stano – NASA SPoRT

The 2013 Experimental Warning Program (EWP) has offered a great opportunity to test the NASA SPoRT / MDL total lightning tracking tool. Part of EWP’s efforts are to demonstrate future GOES-R capabilities, such as the Geostationary Lightning Mapper. This is being done with the pseudo-geostationary lightning mapper products being produced by NASA SPoRT in collaboration with seven ground-based total lightning networks. With total lightning observations (intra-cloud and cloud-to-ground) forecasters are looking for lightning jumps, or very rapid increases in total lightning activity ahead of severe weather. In the past, this has been done by visually inspecting the PGLM data. From previous evaluations by both SPoRT and the EWP, the number one request was for a way to visualize the time series trend of total lightning in real-time. With AWIPS II and the ability to create custom plug-ins, the first effort for this has been developed and is now here in operations at the EWP. One design feature was to make this a manual tool. In other words, it is the forecaster who selects the cell track and not an automated tracker, which traditionally has difficulty with merging and splitting cells or not activating at the proper time. Once the forecaster places two points, the tracker activates and will create a track based on these points.  Each point can be moved individually to adjust the track and the tracker will attempt to maintain the track as new data are ingested.  We wanted to evaluate the utility of the total lightning tracking tool as well as its impact on operations. In only a couple days, the feedback has been great. First, here is an example of the PGLM with the total lightning tracking tool this evening.

The PGLM flash extent density observing a maximum of 49 flashes with the total lightning tracking tool time series (pop-up to left).  The lightning jump can be seen early in the time series as it goes from 20 to 49 flashes in two minutes.

Overall, feedback has been very positive as forecasters have  appreciated being able to visualize the time series instead of creating a mental picture.  Also, the time series plot is pinned to always be on top, which prevents it from being lost behind the D2D display.  Also, the feedback has been very constructive to help improve the look and provide ways to minimize the time impact.  Some of the commentary has focused on modest improvements to the layout and look.

• Add a minimize button to the time series display pop-up.
• Have the time series trend color match the active cell point color for the track.
• Have a way to change the default size of the cell point radius of influence (which determine how much lightning data to query).

The feedback also has included very interesting options to save time in implementation.

• The tracker initiates after two points are plotted.  However, it attempts to extrapolate the cell track after placing one point.  This results in the cell points being very spread out.  Suggest waiting to extrapolate the track until after two points placed.
• Also, when the storms are more discrete, instead of using individual cell points created a small “domain” around the storm cell of interest.  The forecaster selects a “polygon” of where the storm will be and the tracker selects the PGLM value within this domain at each time step. This may be able to be done by using the tools similar to how forecasters plot a warning polygon as well as how that can be edited.  Furthermore, the storm motion could be added to further aid the plot.  The big advantage here is that this polygon may be much quicker to place than several individual cell points.

All of these are very good suggestions and this feedback will be taken back to see what can be implemented. The polygon suggesting is very interesting to consider, while the current cell point method would be most viable in a multi-cellular environment.  Additionally, this feedback has been very useful in that it helps refine the total lightning tracking tool ahead of its next evaluation as part of the Operations Proving Ground later this summer.
Tomorrow should be another good day to gather additional feedback.

UWCTC Captures Developing Severe Convection in SE Kansas

CTC captured developing convection that eventually turned severe in the ICT WFO.  The initial and only UWCTC cooling rate was diagnosed to be strong at approximately ~-22K/15 min (see Figure 1) during the 2332 UTC scan. 

Figure 1.  UWCTC over visible imagery valid at 2332 UTC.  The cooling rate was ~22K/15 min.

The base scan radar imagery out of ICT at 2329 UTC had a precipitation core on radar with approximately 50 dBZ radar reflectivity (Figure 2).  No severe warning was issued at that time (The warning shown on the screen near the echo was issued at a later time).

Figure 2.  Radar imagery from ICT WFO.  Storm of interest is NE of radar site.

A severe warning was issued by the ICT WFO at 0016 UTC for this storm with the threat of quarter size hail and strong winds (Figure 3).  No hail reports were received as of this blog entry for verification of this severe warning.

Figure 3.  SVR from ICT concerning storm of interest.

Figure 4 shows radar imagery valid at 0032 UTC for the same storm.  Notice the stronger reflectivity in the core of the storm.  The strong UWCTC rate had a lead time of ~45 minutes over the severe warning that was issued.  Again, no hail reports were received so far.

Figure 4.  ICT base reflectivity valid at 0032 UTC.

Flash Extent Density Jump

One cluster of storms over southwest Oklahoma produced the most impressive FED signal of the day. While we’ve had a warning out for this storm for some time, no reports have been received, and MESH has kept values generally at or below one inch.

**Update**

One rapidly intensifying cell has shown a lightning jump with up to ~50 flashes/min and is likely producing severe hail per MESH.

PGLM Total Lightning Data Aids in Warning Issuance

A rapid ramp up in total lightning data led to increased lead time for a Severe Thunderstorm Warning this afternoon. The Flash Extent Density product increased to 19 flashes per minute prior to warning issuance.

Flash Extent Density product showing an increase to 19 flashes per minute prior to warning issuance.

Flash Extent Density further increased following the warning as severe hail was reported.

Flash Extent Density product increased to 32 flashes per minute as severe hail was reported.

Frank/Guseman

High and Mid Cloud Contamination Limiting Use of GOES-R CI and CTC Products

Early high and mid cloud contamination from an approaching upper-level jet limited use of both the UAH CI and UW CTC products across northwestern Oklahoma this afternoon. Storms initiated around 3 pm with the first Severe Thunderstorm Warning issued around 345 pm. The UAH CI product never showed any signs of CI due to this cloud contamination, but the UW CTC product did briefly show some signs of severe storm development as it provided an approximate 20 minute lead time on the first warning issuance. Previous shifts had found longer lead times utilizing the CTC product, but the extent of upper and middle cloud contamination was not as pronounced during those cases.

4 panel imagery showing nothing from the CI product. The CTC product did briefly pick up on cooling rates near 15 C/15 min at 2025Z.

Same as above at 2032Z, with CTC showing cloud top cooling rates greater than 20 C/15 min.

CTC product continued increasing to greater than 25 C/15 min with storm motion toward the northeast at 2040Z.

Both the UAH CI and UW CTC products show nothing as mid and high clouds continue streaming in with mature storms at 2045Z.

Frank/Guseman

Large CTC Values Providing Excellent Lead Time for Severe Hail

Developing supercells over the TX panhandle became severe appox 30 to 45 min after a significant CTC signal. This signal is shown below in the upper left corner of the 4 panel. 30 to 45 min. after the minimum CTC value of -33, MESH indicated 1 inch or larger hail. This is displayed in the second image below. Of note is how well the CTC algorithm is performing despite a modest cirrus shield.

Austin

EWP2013 8 May 2100 UTC Mesoscale Discussion

We are actively monitoring convection across western OK and the TX panhandle. At 4 pm our area of operations will be the OUN CWA.

 MRMS QC Composite Refl, MRMS mid-level rotation tracks, MRMS dbz at -20 C, HCA/HSDA

High 50s/low 60s dew points are continuing to pool across western OK as observed on the OK mesonet.

2035Z Mesonet

The OUNWRF appears to be capturing the current dewpoints correctly over Oklahoma, especially in the area where convection is developing. However, the temps ahead of the convection appear to be too high on the OUNWRF. It is possible that this is contributing to the over-development of convection on the OUNWRF (as seen spatially on the simulated reflectivity products).

LAPS analysis from the 1 km OUN domain continues to do a decent job with the placement of the composite reflectivity across western OK. Interestingly enought the 21z LAPS shows a clean swath of 2200 to 2600 J/Kg SBCAPE spreading northward across western north Texas, with another pocket of 2000 to 2500 J/Kg SBCAPE near the OK/KS border, which would be nearer the sfc low which continues to churn E/NE across the TX panhandle.

SFC layer-max base Refl, 1km SBCAPE, 1km sfc Lifted Index, SBCIN

Early convection this afternoon developed in a sct to bkn area of cumulus, with scattered cirrus/stratus spread across Panhandles through western OK. This has resulted in little to no response from the both the GOES-CI and CTC products due to the contamination from the cirrus and stratus. The screen capture below shows the area of intense convection developing over Oklahoma, with little to no apparent signals in the CI/CTC products. This was also the case for several time steps before this image was saved.

CI, CTC, and IR

Nearcast products from CIMSS/GOES have also struggled with the presence of clouds before convective initiation. This is evident from loss of data across western OK and the TX panhandle.

PW Diff, Te Diff low-mid, Convection Index (K^2mm), 780-500mb CAPE

Kurtz/Hatzos