Sunday, 22 January 2012
Precipitable Water Vapor in and Around Tropical Cyclones in the Caribbean: 2007-2010
Hall E (New Orleans Convention Center )
This study analyzes precipitable water vapor (PWV) in and around tropical cyclones (TC) over the Caribbean region. PWV is highly variable in time and space, and it is a potential energy source for tropical cyclone development. To characterize the PWV profile in and around TCs, observations of PWV are compared to PWV from an operational weather forecasting model for the years 2007-2010. PWV observations were gathered from the Suomi Network of ground-based Global Positioning System (GB-GPS) stations within a 1,000 km radius of a TC's center and categorized by storm strength. Maximum wind speeds and coordinates of storm centers were obtained from the North Atlantic Basin Hurricane Dataset. The Global Forecast System (GFS) model initializations of PWV were then linearly interpolated to the GB-GPS at a 6-hourly time resolution for comparison. The statistical analysis of PWV from the GPS and the GFS revealed a consistent overestimation of PWV in the GFS. This overestimation ranged from 2-4 mm at distances beyond 200 km from the storms' centers. However, at distances within 100 km from the storms' centers, the average PWV was underestimated by the GFS in the tropical storm category. The GFS model error was greatest at approximately 200 km from storm centers. Statistics correlating PWV and storm strengths of Category 3 and higher were inconclusive due to lack of observations. This study thus provides adequate analysis of PWV for TC strengths below Category 3, and this can be useful for improving tropical cyclone forecasts.