Verification of Thunderstorm, Mesocyclone, and Tornado Forecasts from an Experimental Warn-on-Forecast System
Abstract
NOAA's Warn-on-Forecast project is an initiative to provide probabilistic guidance for convective storm hazards on time scales between a typical watch and warning product issued by the National Weather Service. An experimental Warn-on-Forecast convection-allowing ensemble analysis and prediction system has been used to produce real-time forecasts for more than 90 cases during the spring and summers of 2017-2019. This Warn-on-Forecast System (WoFS) utilizes rapidly cycled, ensemble Kalman filter-based assimilation of Doppler radar and satellite cloud water path observations to produce accurate analyses of convective storms. Short-term (0-6 hr), 18-member forecasts are then launched from these analyses up to twice an hour to provide probabilistic guidance of hazards within individual storms.
The quality of WoFS forecasts is assessed using an object-based verification framework. Simulated radar reflectivity and updraft helicity are used to identify objects associated with thunderstorms and mesocyclones, indicative of a severe thunderstorm, respectively. WoFS forecast objects are verified against objects identified in Multi-Radar Multi-Sensor gridded radar reflectivity and azimuthal wind shear observations. A conditional probability of a tornado occurring within each predicted mesocyclone object is prescribed using an empirical relationship with the upstream Significant Tornado Parameter. Object matching then allows the quality of WoFS thunderstorm, mesocyclone, and tornado forecasts to be assessed in both deterministic and probabilistic frameworks. Bulk measures of the accuracy of WoFS predictions and reliability of probabilistic guidance will be presented as well as comparisons of forecast skill across different convective modes and mesoscale environments.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A34C..05S
- Keywords:
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- 3329 Mesoscale meteorology;
- ATMOSPHERIC PROCESSES;
- 3354 Precipitation;
- ATMOSPHERIC PROCESSES;
- 3355 Regional modeling;
- ATMOSPHERIC PROCESSES;
- 4313 Extreme events;
- NATURAL HAZARDS