A Geostationary Satellite Technique to Estimate Tropical Cyclone Size

The large differences in size and strength of TCs result in considerable variability in their impacts on both marine interests at sea and inhabited coastal areas during close approach and landfall. Larger storms may have increased storm surge, increased oceanic upwelling, and a wider area in which flooding and damaging winds may occur as well as a larger area of rainfall. Thus a robust and accurate depiction of the extent of damaging winds is important both to directly prepare for impacts and also to properly initialize numerical weather prediction (NWP) forecasts of future TC motion, intensity, and wind structure.

The current study extends research based on the deviation angle variance (DAV) technique, which utilizes digital brightness temperatures from long-wave IR satellite images to objectively measure the symmetry of a TC solely based on a comparison of the gradient vectors of brightness temperatures from an actual TC with the gradient vectors of an ideal, symmetric vortex. The DAV technique has already been utilized to obtain TC intensity and as a means of identifying cyclogenesis in the Atlantic, eastern North Pacific and western North Pacific basins. In this study, the spatial-temporal structure of the DAV signal for TCs is utilized along with wind radii from the Extended Best Track and information from the Statistical Hurricane Intensity Prediction Scheme (SHIPS) model to provide a multiple linear regression technique that objectively calculates the wind radii for a given TC on a half hourly basis. The results from the technique presented here are tested against TCs with aircraft reconnaissance occurring within 3 hrs of a Best Track estimate and result in a model that predicts the symmetric and asymmetric components of the wind radii on a half-hourly basis. The model will provide objective wind-field estimates in real-time that may be used for NWP model initialization.

Approximately 4708 half-hourly images from Geostationary Operational Environment Satellite 12 (GOES 12) brightness temperature images were processed from 21 TCs from the years 2004-2010 that had extensive in-situ observations. Maps of the DAV with respect to time provide information on the symmetry of TCs. The spatiotemporal information in these maps, along with information from Best Track and the SHIPS model, has been utilized to create a multiple linear regression model. This objective model was utilized to estimate the 34-, 50-, and 64-kt wind radii. Symmetric and asymmetric models were derived. In this presentation we will show the results of the analysis including errors for the three wind radii and also compare reconstructed wind fields with observed wind fields from 2011 and 2012. 225.56 on 11-5-2013-->