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.
Sim Aberson administrative
information
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Last modified: 5/24/99