18th Conference on Weather Analysis and Forecasting and the 14th Conference on Numerical Weather Prediction


Verification of RAMS forecast sea breezes and thunderstorm initiation over east-central Florida

Jonathan L. Case, NASA Kennedy Space Center/Applied Meteorology Unit/ENSCO Inc., Cocoa Beach, FL; and J. Manobianco, A. V. Dianic, D. E. Harms, and P. N. Rosati

This paper describes a portion of the Applied Meteorology Unit’s (AMU) evaluation of the Regional Atmospheric Modeling System (RAMS) contained within the Eastern Range Dispersion Assessment System (ERDAS). ERDAS is designed to provide emergency response guidance for operations at the Cape Canaveral Air Force Station (CCAFS) and Kennedy Space Center (KSC), Florida, in the event of an accidental hazardous material release or an aborted vehicle launch. The evaluation protocol is based on the needs of Eastern Range safety and weather personnel, and designed to provide specific information about the capabilities, limitations, and daily use of RAMS in ERDAS for operations at KSC/CCAFS. The prognostic data from RAMS is available to ERDAS for display and input to the Hybrid Particle and Concentration Transport (HYPACT) model. Thus, the accuracy of the HYPACT model is contingent upon the prognostic data from RAMS.

In ERDAS, RAMS is run in real-time on four nested grids with horizontal resolutions of 60, 15, 5, and 1.25 km using full microphysics on all grids. The model is initialized twice-daily at 0000 and 1200 UTC using operationally-available observational data and run for a 24-h forecast period on local workstations with multiple processors. The 12-h forecast from the National Centers for Environmental Prediction Eta model provides the background field for the initial condition and the Eta 12-36-h forecasts are used as boundary conditions.

As part of the RAMS evaluation protocol, the AMU conducted a subjective verification of the RAMS forecast East Coast Sea Breeze (ECSB) and thunderstorm initiation during the Florida warm season. The RAMS forecast ECSB was verified within the KSC/CCAFS wind-tower network during the 1999 and 2000 Florida warm seasons. The occurrence and timing of the ECSB was evaluated for the operational 4-grid configuration of RAMS at 12 selected KSC/CCAFS wind towers over the coastal barrier island, Merritt Island, and mainland Florida from May to September. For the 2000 warm season, the AMU also verified the ECSB for a 3-grid configuration of RAMS, in which the innermost 1.25-km grid was withheld during integration. In addition, the AMU conducted an ECSB evaluation comparing the 4-grid RAMS and Eta model forecasts at the Shuttle Landing Facility. The results show that the 4-grid configuration of RAMS is a better predictor of the ECSB than the coarser resolution version of RAMS and the Eta model.

The AMU conducted the RAMS thunderstorm initiation verification during the 2000 warm season on the innermost 1.25-km grid. Grid 4 was divided into 6 regions, 3 each inland and coastal, to determine the skill of RAMS in specific areas of grid 4. A predicted thunderstorm was identified by a minimum upward vertical velocity at ~7 km height in conjunction with a minimum forecast rainfall rate. An observed thunderstorm was identified by lightning data from the Cloud-to-Ground Lightning Surveillance System. The first forecast thunderstorm was verified against the first cloud-to-ground lightning strike in each zone on a daily basis. The results show that the 1200 UTC forecast cycle has greater skill in forecasting thunderstorm initiation than the 0000 UTC forecast cycle; however, the model overall has limited skill in identifying the correct region and timing of thunderstorm initiation and development. This talk will summarize and present the details of the ECSB and thunderstorm initiation results.

extended abstract  Extended Abstract (116K)

Poster Session 2, Poster Session - Numerical Data Assimilation or Analysis: Case Studies and Validation—with Coffee Break
Tuesday, 31 July 2001, 2:30 PM-4:00 PM

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