EWX Meso Update 2230UTC

Forecaster comments from the EWP blog...

Issued a (experimental) warning on a cell for hail and wind based on radar trends and the fact that this storm was moving into a good environment.  The above image of radar reflectivity shows the storm moving southeast into a good theta-e environment depicted by the yellow axis on the above image.  The theta-e imagery is CIMSS-NRE Layer GOES Vertical Theta-e Diff Low-Mid Img

EM Discussion @ 21Z

Experimental Area Forecast Discussion (AFD) from EWP blog...

Location: Latest guidance supports continued development of strong to severe thunderstorms moving across McColloch, San Saba, Llano, San Saba and Mason counties.

Impacts:  primary impact will be large hail and damaging winds.  there is still potential for isolated tornadoes.

Met discussion:  OUNWRF showed evidence of moisture convergence on the h8/h7 wind and theta E H8-7 layer; MRMS Max hail size estimated 1.5″ hail;  UAH CI strength of signal showed 80-100 values over the areas of favorable moisture convergence; CI-CTC projected new development over Llano county.

EWP: UW-CTC over Texas

Over the past hour we have been evaluating the UW-CTC output with developing convection associated with an outflow boundary from a convective complex over Central Texas. 

Figure 1 shows the the GOES IR-window and visible observations at 1915 UTC 07 May 2012 (top) and the UW-CTC rate (bottom left) and associated SJT composite reflectivity (bottom right).

Figure 2 is the same as Figure 1, except valid ~2000 UTC 07 May 2012.

As can been seen in the images above, the UW-CTC rate at 1915 UTC (~ -15 K / 15 min) proceeded the development of a 56 dBZ composite reflectivity echo by 45 minutes.  Additionally this storm was producing a 0.80" radar-estimated maximum expected hail size by 2029 UTC.  This is one of hopefully, many examples, demonstrating how the quantitative measure of cloud top cooling rates can provide prognostic value of strong radar reflectivity and formation of near-severe hail.

EWP Underway: UW-CTC and Echo Top Heights

The EWP @ HWT is underway.  While we're currently getting spun up getting data displayed, etc., the first conversation related to UW-CTC (cloud-top cooling rate) was not warning related, but aviation related with a representative from the Houston CWSU.  The representative was interested in the validation study performed by UW/CIMSS of the UW-CTC to future NEXRAD 18, 30, and 50 dBZ echo top heights, especially over their Gulf of Mexico responsibility region as well as the Houston TRACON (terminal radar approach).  Since the results of the echo top height were not included in the HWT training, we'll provide the echo top height analysis to the Houston CWSU.

Justin
UW/CIMSS

EWP underway

NWS forecasters and visiting scientists participating in the Monday afternoon overview briefing.

The Experimental Warning Program (EWP) portion of this year's Spring Experiment is now underway. This week we have 4 NWS forecasters visiting the HWT. During the first hour of the day from noon to 1pm the forecasters participated in a short overview briefing and then moved into the HWT to familiarize themselves with the data in AWIPS II. During this time, 2 of the forecasters who were unable to run through the Weather Event Simulator (WES) training case were able to do so. Currently the forecasters are focused over southern TX where a severe threat is currently ongoing. We may not issue any warning tonight as the forecasters are still getting comfortable working in AWIPS II.

NWS forecasters running through the 24 May 2011 WES training case prior to operations.

EFP CI and Severe desks

EFP CI (left) and severe (right) desks during the morning forecast period.

This year's Experimental Forecast Program (EFP) contains two main focus areas... convective initiation (CI) and severe. Both desks are using experimental high-resolution numerical models and ensembles of those numerical models (CAPS ensemble, SSEO, AFWA) to forecast the first occurrence of a 35 dBZ radar echo (CI) and the subsequent severe weather. They will be examining some of the simulated satellite imagery and unique GOES-R band differences during their forecast operations that we provide them from the NSSL-WRF 0Z 4km model, as well as from some of the members of the CAPS ensemble.

2012 Spring Experiment begins

Visiting scientists and forecasters participate in the Monday morning briefing during the Experimental Forecast Program

Today marks the beginning of the 2012 Spring Experiment. The experiment will run through June 15th this year and we have invited 24 NWS forecasters and 15 visiting scientists to participate in a wide range of activities all focused on the forecast and warning of convective initiation and severe weather. The Spring Experiment consists of 2 unique programs, the Experimental Forecast Program (EFP - which focuses on experimental numerical model guidance of convective initiation and severe weather) and the Experimental Warning Program (EWP - which focuses on the short-term warning of severe weather). The GOES-R component of this year's Spring Experiment will mainly be focused within the EWP. Products being demonstrated include the pseudo-Geostationary Lightning Mapper total lightning, convective initiation nowcasting, cloud-top cooling rates, simulated GOES-R ABI imagery and associated band differences, 0-6 hour GOES sounder-based 'Nearcast', and GOES sounder RGB airmass product. Constant forecaster interactions during real-time testing of GOES-R Proving Ground products will drive the feedback gathered from this year... which you will see posted in near-real-time on this blog. In addition, visiting scientist participants will be encouraged to blog about their experiences while they are interacting with the forecasters. Activities run from 8am to 10pm throughout most of the week, with a greater emphasis on severe weather warning as the day progresses.

14 April 2012 - Unique applications of NDVI and GOES dryness products

Bob Rabin from NSSL/UW-CIMSS provided me with a couple interesting images late last week in preparation for the upcoming events on Friday/Saturday. I thought I would share them here with you all to get a new perspective on a product that we used extensively within the Fire Weather Experiment last Fall to monitor vegetation and surface moisture. Bob Rabin gathers and generates NDVI composite imagery as well as GOES derived surface dryness values that we provide within SPC operations in support of their fire weather forecast desk. The products were mainly intended to monitor for dry vegetation and anomalously dry surface conditions that would be a potential hazard for fires. In these examples, Bob pointed out that the NDVI and GOES surface dryness products were both picking up on a very well defined dry / moist boundary across much of KS, OK and TX (see images below).

Continental US NDVI composite from 9 April 2012. Green areas indicate regions with significant green vegetation cover, while yellow and brown regions indicate decreased green vegetation cover. Note the pronounced gradient in green vegetation along a line extending from western KS and OK into central TX.

Continental US GOES surface dryness composite from 11 April 2012. Green areas indicate regions with significant surface moisture mesurements, while yellow and red regions indicate dry surface measurements. Note the pronounced gradient in surface moisture along a line extending from western OK into central TX. It would be interesting to examine how these surface moisture boundaries interacted to potentially enhance convective initiation set up by circulations due to differential heating. In fact, one SPC forecaster noted this in a Mesoscale Discussion issued on the 14th prior to convective initiation along the TX/OK border. In addition, it would be interesting to examine the interaction these surface moisture boundaries have on the evolution of the dryline. It is exciting to see applications of satellite imagery used to detect these features not easily observable from other systems in such a constant and relatively highly spatial manner.

14 April 2012 - Simulated Band Difference

Part of the NSSL-WRF simulated satellite imagery that we get from CIRA includes a band difference unique to GOES-R that we began looking at during last year's Spring Experiment. One of the advantages of simulating satellite data from a model is that we have the opportunity to produce channels that we don't have currently, and we take full advantage of this by producing all 9 of the non-solar GOES-R IR bands. The 10.35 micron channel is a very clean window, and thus is very sensitive to surface temperature. The 12.3 micron channel however is sensitive to low- and mid-level water vapor. As moisture moves into a clear pixel area, the 12.3 micron brightness temperature will decrease, whereas the 10.35 micron temperature should stay the same. When this occurs, the 10.35-12.3 micron channel difference will become strongly positive and indicates areas of moisture convergence or pooling, which can lead to destabilization and subsequent convective initiation.
Unfortunately, because the imagery is generated by a numerical model, it is a) not an observation and b) only available on an hourly timescale. However, we can use the imagery generated from the model as a experimental tool to demonstrate some of the unique things we can do once we have the increased spectral resolution of the GOES-R Advanced Baseline Imager (ABI). In this example from the 14 April 2012 outbreak the 10.35-12.3 micron channel difference is useful in identifying the evolution of the dryline across western KS, OK and TX from 1900 UTC on the 14th to 0100 on the 15th (see images below). As moisture converges at the surface, the difference becomes more positive. These positive values show up as yellow, orange and red on the images below. The edge of the dryline is easy to detect and follow using this simple band difference within the NSSL-WRF. It will be very interesting to see observations of this band difference, and other imagery techniques such as RGBs, every 5 minutes over the continental US once we have the GOES-R ABI available to us.

14 April 2012 - Sounder Airmass RGB

Well, it's not quite the Spring Experiment yet, but we did have a significant severe weather event over the plains this past weekend that I figured would be a good opportunity to capture some of the GOES-R Proving Ground products that we receive at the Storm Prediction Center and Hazardous Weather Testbed. We will start with the GOES Sounder Airmass RGB that is provided to us by CIRA and NASA SPoRT. RGB simply stands for Red-Green-Blue, which is a composite image created by combining three separate channels or channel differences into one image. This technique helps us identify specific features in the atmosphere without the use of complex derived products. The airmass RGB is a combination of thermal infrared, water vapor and ozone channels that help us identify regions of warm and moist versus cold and dry airmasses, spin in the atmosphere and jet streaks. The airmass RGB has been used extensively over Europe using the Meteosat Second Generation satellite, which has similar spectral channels to what will be available on the GOES-R Advanced Baseline Imager (ABI). Current GOES imagers do not contain the spectral bands necessary to generate this product, but we are able to simulate the RGB using the GOES sounder, which does have some similar channels to the ABI. Unfortunately this data only arrives once hourly from the sounder, but when GOES-R is launched, we will be able to create this product every 5 minutes over the continental US.
Below is a time-series of the SPC's outlooks from day 7 up until the event on Saturday 14 April 2012 from the SPC Facebook page. You can see clearly that the SPC had a good handle on the threat a week in advance and that the threat area depicted on day 1 well outlined the events that occurred in NE, KS, OK and IA. Preliminary storm reports from the SPC website indicate 135 tornado reports (likely will end up being about 75 individual tornadoes following official surveys) occurred during this event, with what appears to be several long tracks across OK and KS.

If we take a look at the sounder airmass RGB product at 12 UTC on 14 April 2012 (top image below), we can see a strong center of circulation over CA/AZ/UT/NV with indications of a significantly lowered tropopause, associated jet streaks and high PV (red hues) within the circulation and extending along the Pacific coast up into Canada. This can be confirmed by overlaying the tropopause pressure from the RUC analysis (middle image below) or the the 500 mb heights and vorticity (bottom image below).

If we move forward to 15 UTC (image below), just prior to initiation in KS, we can begin to see evidence of a moisture boundary (blue-to-green hue gradient) setting up along a line extending from NW KS near the KS/NE border down into the OK panhandle and down into west TX. Initiation in southern KS and down through the OK panhandle into TX would occur along a dryline located in this area, which is likely what the airmass RGB is picking up at this time.

Moving forward to 02 (top image below), 03 (middle image below) and 04 UTC (bottom image below) on 15 April 2012, the moisture gradient feature really begins to tighten up and better define itself as the dryline continued to evolve and the Pacific cold front approached, initiating a line of storms extending into central TX.