Nearcast in a warning environment

EWP forecasters are currently monitoring severe weather over southern TX and issuing experimental warnings for storms that have been producing severe hail.  One of the forecaster groups localized for the forecast office in Austin, TX has been monitoring GOES-13 IR with the UW-CIMSS differential theta-e product overlaid.  Their goal is to identify the near-storm environment that the currently severe storm is moving into to aid in the warning decision making process.  This provided a very good example how the Nearcast product maintains previous observations where new observations cannot be made due to cloud cover.  This can be useful in providing high-resolution observational data key to identifying localized regions of instability that cannot be obtained through other means.  In this case the forecasters decided to issue an experimental severe thunderstorm warning at 2228 UTC based on the current representation of the storm on radar and the Nearcast differential theta-e fields.

EWX Meso Update 2320 UTC

Forecaster comments from the EWP blog...

The first image below shows cloud top cooling rates at 1715Z.  Note the values of almost -35 K in the light blue over west central TX.    The second image below of IR satellite imagery at 1745Z, depicts the beginning phases of strong convection in the same region as the cloud top cooling noted 30 min before strong convection initiated.  The CIMSS cloud top cooling product correctly predicted the formation of a  complex of strong storms that later became severe during the late afternoon/early evening hours.

EWP: UW-CTC in areas of thin cirrus

The montage below demonstrates the improvement to the UW-CTC products to operate in areas of thin cirrus cloud cover during daytime hours.  This improvement was one of the largest deficiencies identified by forecasters in previous testbeds.  Diagnosing cloud-top cooling rates in presence of thin cirrus clouds is possible by inclusion of GOES daytime optical depth retrievals.   The UW-CTC rate at 2145 UTC 07 May 2012 was approximately -6 K / 15 min (lower left, figure 1); with further cooling of ~ -18 K / 15 min at 2215 UTC 07 May 2012 (lower left, figure 2).  By 2245 UTC the Dallas-Fort Worth radar indicated 50-55 dBZ composite reflectivity.  Another cell further west was not captured by the algorithm, possibly due to its position closer to colder anvil temperatures.

Figure 1. 

 Figure 2.

Figure 3.

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.