ADAPTIVE OBSERVATIONS TO IMPROVE HURRICANE TRACK FORECASTS

Principal Investigator: Sim D. Aberson

Collaborating scientist(s):
Jimmy Franklin (NHC/TPC)
Sharan Majumdar (PSU)
Craig Bishop (PSU)


Objective: Evaluation of methods to target aircraft and dropwindsonde observations to optimally improve tropical cyclone track forecasts.
Rationale: From 1982-1996, HRD has completed a series of synoptic flow experiments in which dropwindsondes gather vertical profiles of wind, temperature, and humidity within about 1000 km of the center of potentially landfalling tropical cyclones in the North Atlantic Ocean. These observations have been shown to reduce errors by up to 30% on averge, an improvement equivalent to that obtained operationally during the last two decades. Since such observations have been shown to significantly impact track forecasts, a means to target such observations to optimally affect the forecasts is being developed.
Method: The method of breeding the fastest growing modes in the operational global models used at the National Centers for Environmental Prediction (NCEP) and VICBAR provide information concerning locations of likely uncertainty in both initial conditions and forecasts. The ensemble ttransform technique will be used to find target locations from the models. By taking observations in these locations and outside of these locations, studies of the effectiveness of such a method are to be pursued. The NCEP global model is to be perturbed using different configurations of observations based upon information from the bred growing modes, and other operational models will be run based upon these global model runs. The overall impact of these observations will be assessed.


Accomplishment: Twenty-five synoptic surveillance missions are vailable for evaluations. Results can be seen here. Targeting a few observations in particular regions in the TC environment has been shown to improve forecasts more than average throughout the environment.
Key references:

Toth, Z., and E. Kalnay, 1993: Ensemble forecasting at NMC: The generation of perturbations. Bull. Amer. Meteor. Soc., 74, 2317-2330.

Bender, M. A., R. J. Ross, R. E. Tuleya, and Y. Kurihara: 1003: Improvements in tropical cyclone track and intensity forecasts using the GFDL initialization system. Mon. Wea. Rev., 121, 2046-2061.

Lord, S. J., 1993: Recent developments in troical cyclone track forecasting with the NMC global analysis and forecasting system. Preprints of the 20th Conference on Hurricanes and Tropical Meteorology, San Antonio, Amer. Meteor. Soc., 290-291.

Aberson, S. D., and M. DeMaria, 1994: Verification of a nested barotropic hurricane track forecast model (VICBAR). Mon. Wea. Rev., 122, 2804-2815.

Bishop, C. H., and Z. Toth, 1999: Ensemble transformation and adaptive observations. Accepted by J. Atmos. Sci.


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Last modified: 5/24/99