© 2019 Terry Swails

STORMS GONE, SO IS THE WARMTH...

April 18, 2019

For the first time this spring thunderstorms brought severe weather warnings to parts of my area in eastern Iowa. While there were no confirmed reports of severe weather it was a good warm-up for what will inevitably come, tornado warnings.

 

The science of tornado forecasting has made steady progress over the years with average lead times in strong twisters now more than 10 minutes. Going forward, the goal is to increase that time even more with an additional focus on geographically tightening the area warned.

 

Here's an example of what I'm talking about. This was the area warned in the 2011 Tuscaloosa tornado  which killed more than 30 people. The tornado track is represented by the black line running through the red warning polygon. It was a great warning and saved countless lives but there were many people in the warning box who were not impacted yet still forced to take shelter.

Now the NWS is working on a project called Warn-on-Forecast. A more precise threat map based on PHI (probabilistic hazard information), which can ingest both conventional current data such as radar, satellite and surface observations, as well as any high-resolution short tern models, and can be adjusted in real-time by the forecaster. In the example below, notice the tighter warning plume and emphasis on the area most likely impacted. Not only could this increase lead time by more than a half an hour, it could be updated and altered as often as every minute. Today's warning polygons can remain in place unchanged up to 45 minutes.

At some point this will revolutionize replace the current system. This is going to be a terrific upgrade. Below is more information on the Warn-on-Forecast project from the National Severe Storms Laboratory.

Warn on detection (The present)

Currently, the NOAA National Weather Service (NWS) does not issue warnings for local severe weather until they see an early signal on radar, or the weather hazard is spotted. This approach provides the public with an average of 13 minutes advance notice before a tornado strikes. For some needs, this is not enough lead-time to move people to safety.

Warn-on-Forecast (The Future)

Warn-on-Forecast researchers work to combine high-resolution surface, satellite, and radar data into an optimal set of analyses to initialize ultrahigh-resolution surface, satellite, and radar data into an optimal set of analyses to initialize ultrahigh resolution computer models that will predict specific weather hazards 30-60 minutes before they form. This advanced modeling system will predict probabilities of a hazard occurring, the confidence in the path, and adjust to trends in the threat level based on new weather observations, and rapid and adaptive radar scanning capabilities.

Warn-on-Forecast and FACETs

Warn on Forecast is the foundation of the new Forecasting a Continuum of Environmental Threats (FACETs), a proposed next-generation severe weather forecasting concept. FACETs aims to build a modern, flexible system that forecasters can use to communicate user-specific , understandable weather threat information. FACETs will serve as a “delivery mechanism” for WoF predictions of storm-specific hazards such as tornadoes, large hail, and extreme local rainfall. This work will enable the current NWS warnings paradigm to move beyond a binary yes/ no warning process (from being in our outside the warning polygon) toward one which provides a more detailed threat assessment allowing various classes of users to base decisions on their specific situations and vulnerabilities. Decision-makers could set their own hazardous weather threat thresholds based on their specific needs.

Testing the Warn-on-Forecast concept

As new Warn-on-Forecast technologies emerge, they are tested in simulated forecasting and warning exercises in the NOAA Hazardous Weather Testbed (HWT), ensuring an efficient transition into forecasting operations. In the HWT, Warn-on-Forecast scientists and NWS forecasters have already evaluated multiple building blocks of a future Warn-on-Forecast system, including: • Phased Array Radar and its ability to provide more frequent updates than current NWS radars, • Different techniques to feed radar data into forecast models accurately and quickly • Different suites of forecast models that can be combined into a single system representing all possible outcomes for a given weather event, and • Development of strategies that allow forecasters to rapidly interpret computer-model guidance and add value in generating prototype forecast products. Supporting a Weather Ready Nation The Warn-on-Forecast activity supports requirements and activities documented in the NWS Weather Ready Nation road map, the NOAA 5-year Research and Development Plan, and recommendations in the National Academy of Science 2012 report, “The National Weather Service Modernization and Associated Restructuring.” Warn-onForecast is led by NSSL and represents a collaborative effort across several NOAA groups including the Earth System Research Laboratory, the Storm Prediction Center, and the Norman NWS Forecast Office. Academic collaborators are the Center for Analysis and Prediction of Storms, and the Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma................................................................................................................................................

 

With a strong cold front now well to the east Thursday's weather will be a far cry from Wednesday. Brisk winds and clouds will combine with highs 20-25 degrees cooler to make for a rather raw day. While it's bound to be a set back it's only a temporary downturn and readings will already be on the way up by the start of Easter weekend. Here's the forecast for Cedar Rapids which will be similar for much of area.

 

That's a wrap. And speaking of that you'll need a wrap today with the much cooler weather. Have a good one and of course, roll weather...TS

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