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Experiment mixes research and operations to improve severe weather warnings

By Susan Cobb

Just as the right mix of atmospheric conditions triggers thunderstorms, the NOAA Hazardous Weather Testbed 2007 Spring Experiment hopes the right mix of experience, theory and operations will trigger the improvement of severe weather forecasts and warnings.

The 2007 Spring Experiment is drawing more than 60 researchers and forecasters from government agencies, academia and the private sector to change roles for a week at the National Weather Center in Norman, OK. The exchange allows National Severe Storms Laboratory (NSSL) researchers and collaborators to immerse themselves in the challenges of front-line forecasting while giving forecasters a chance to examine emerging scientific and technological advances. Both will walk away from the experience with increased knowledge of thunderstorm processes that will improve forecasts and vital forecasting and warning tools. The experiment runs from mid-April through the first part of June—taking advantage of the active spring severe weather season that affects large parts of the nation.

Although it’s the seventh year for the experiment, this is the inaugural year for the new Hazardous Weather Testbed facility, strategically located in the recently built National Weather Center between the operational forecast areas of the NOAA Storm Prediction Center and the NOAA National Weather Service Norman Forecast Office (WFO-OUN). These two offices, along with the NOAA National Severe Storms Laboratory, are leading HWT spring experiment activities. Researchers from the NOAA-University of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) are also participating in the program.

There are two main areas of focus in the 2007 Spring Program: severe weather forecasts and severe weather warnings.

Severe weather forecasts

The goal of the Experimental Forecast Program (EFP) is to develop forecasts that could predict severe weather a week in advance. Studies have shown people are more likely to seek shelter if they have been made aware of the severe weather threat prior to the issuance of a warning, such as through a severe weather watch. Accurate severe weather watches are dependent on forecasters being able to properly predict not only where and when severe thunderstorms will develop and how they will evolve over the next 4-8 hours, but also what kinds of storms are most likely to occur – single-cell, multi-cell, or supercell. Each poses a different type of threat.

The EFP is addressing this issue by testing and evaluating a number of daily, real-time Weather Research and Forecasting models (WRF) over domains covering much of the continental U.S. One highlight of the experiment is a high-resolution WRF ensemble called Storm Scale Ensemble Forecast (SSEF). SSEF represents an unprecedented real-time computational achievement and is part of a three-year project that will test and refine a convection-allowing ensemble to provide probabilistic guidance on high impact convective weather events. SSEF will do this by quantifying aspects of uncertainty in the forecast product and offering insights about a possible range of solutions.

Another ensemble model under evaluation will be a mesoscale model that assimilates hourly surface data. Since a key aspect in forecasting convective initiation is the specification and prediction of the mesoscale environment, accurate hour-by-hour analyses are an important component of the forecast process. Teams of forecasters and researchers will evaluate this ensemble and compare the output with the hourly SPC mesoscale analyses.

Severe weather warnings

The other focus of the 2007 Spring Experiment is the Experimental Warning Program (EWP). Early and precise warnings will help forecasters reduce false alarms and allow warnings to be more focused on the people who are truly in danger. NSSL researchers and their collaborators hope to detect and predict mesoscale and smaller weather hazards on time scales of minutes to a few hours, and on spatial scales from several counties to fractions of counties.

Teams participating in the Experimental Warning Program will focus on the shorter-term convective weather warning needs of forecasters by testing new hazardous weather services, products, and applications in a real-time operational setting. Successful results will help improve the skill of severe weather warnings issued by the National Weather Service.

Researchers and forecasters will also test new weather surveillance tools, such as NSSL’s phased array radar and 3-D Lightning Mapping Array, and the National Science Foundation-sponsored CASA radars. They will also examine new scientific concepts that will make severe weather warnings much more precise in space and time.

Several collaborators are providing valuable research and computing resources, some of which are available for the first time, allowing for significant improvements in precision. Single models are being provided by the NOAA Environmental Prediction Center and the National Center for Atmospheric Research. In addition, the Center for Analysis and Prediction of Storms at the University of Oklahoma, as part of the NSF Program Linked Environments for Atmospheric Discovery (LEAD), will provide an ensemble of high-resolution models run at the Pittsburgh Supercomputing Center. High speed Internet access links these resources by National LambdaRail to the HWT in conjunction with OneNet and a use of resources provided by Cisco Systems.

The Hazardous Weather Testbed emerged from the mutual interests of forecasters from the SPC and researchers from NSSL, and was inspired by the culture of collaboration that already existed between researchers and the WFO-OUN forecasters.

5/22/07

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