Developing ‘First-Guess’ Wind Fields For Tropical Cyclone Analyses In H*Wind

A theoretical wind profile algorithm is implemented into a hurricane wind analysis tool to improve a 2-dimensional objective wind analysis. Validation of hurricane surface wind speeds from remote sensing technology has been difficult due to a lack of sufficient storm data needed for the National Oceanic and Atmospheric Administration Hurricane Research Division Real Time Hurricane Wind Analysis System (H*Wind) to accurately describe the surface wind speed field. H*Wind incorporates real time tropical cyclone observations, fits them to a background field and then plots the observations relative to the storm. Researchers can then use the graphical interface of H*Wind to objectively analyze the wind structure of the tropical cyclone. The aim of this research is to develop a better ‘first-guess’ background wind field for H*Wind with which to compensate for the limited amount of storm data. The improved wind fields are then used to analyze the wind speed measurements of satellite observation platforms. By using a theoretical wind profile model, scaling parameters are empirically estimated to generate idealized radial wind profiles. Then, using theoretical wind-pressure relationships within tropical cyclones, the radial wind profiles are adjusted incrementally based on their proximity to the area of maximum winds. Finally, the modified radial wind profiles are populated for every degree azimuth around the cyclone center to create an idealized depiction of hurricane wind structure. The profiles were integrated into H*Wind as a background wind field. For the Atlantic hurricanes tested, the background field slightly improved H*Wind’s ability to accurately describe tropical cyclone surface wind speeds. Comparisons of H*Wind analyses with and without the new background field will be presented. The comparisons will test the soundness of the ‘first-guess’ field concept in creating improved fields for use in current validation studies of satellite-derived surface winds in tropical cyclones.