GEOS-Exp 2km Severe Weather Modeling Capabilities Highlighted In 2024 HWT Spring Forecast Experiment
This past spring, NASA GMAO members Bill Putman, Scott Rabenhorst, and Gary Partyka were asked to take part in the 2024 Hazardous Weather Testbed Spring Forecast Experiment (HWT SFE). This annual event, organized by NOAA’s Storm Prediction Center (SPC) and National Severe Storm Laboratory (NSSL), brings meteorologists and atmospheric scientists from various agencies together to test and improve both new and existing prediction methods of severe hazardous weather. The study took place April 29 – May 31, 2024, in Norman, Oklahoma, and compared the daily performance of several high-resolution (1- to 3-km grid) numerical weather prediction (NWP) models in forecasting and modeling severe convective weather with one another to the observed conditions. One of these models was the GMAO’s own GEOS-Exp 2km, an experimental, high-resolution version of the flagship GEOS model.
While each NWP model in the experiment represents advancement and improvements in weather forecasting, the NASA GEOS-Exp 2km model is the only one that is global in the entire experiement pool. All other models in the study utilize a domain focusing on CONUS, but GEOS-Exp 2km utilizes a global stretched-grid scheme with 2-km resolution over CONUS and 12-km (0.25 degree, the usual GEOS-FP resolution) at the anti-pole. Figure 1 depicts the week-by-week breakdown of GEOS-Exp 2km’s outputs during the study, showing helicity tracks overlayed with severe thunderstorm and tornado warning polygons issue by the NWS. Numerous outbreaks of severe weather occurred during the study, leading to a total of 6469 storm reports to the NWS – 3904 wind, 1977 hail, and 589 tornado. The geographic distribution of severe weather activity varies from week-to-week, enveloping most areas of the US east of the Rocky Mountains. Spatial identification of convective cells with strong updraft helicity was readily apparent for several events during the experiment, which is a phenomenal advancement in the forecasting of severe/tornadic weather for any NWP model in history.
The animation above covers the same time period of the study and not only shows helicity and warning polygons as in Figure 1, but also shows simulated radar reflectivity and CAPE (convective available potential energy) – one of the key ingredients in the formation of severe convective weather. Note the regions of convective precipitation formed along heightened CAPE values, igniting storms and causing most of the severe weather that occurred (regions of precipitation formed due to synoptic forcings are visible as well). Warning polygons remain on the animation for a 24-hr period. Significant outbreaks occurred May 6-9, May 21, and May 23-26.
References:
“2024 Spring Forecasting Experiment.” NOAA National Severe Storms Laboratory, https://hwt.nssl.noaa.gov/sfe/2024.
