92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012
A New Approach to Improved Inland Wind Forecasts for Landfalling Tropical Cyclones
Hall E (New Orleans Convention Center )
Bryce Paul Tyner, North Carolina State University, Raleigh, NC; and A. Aiyyer

Developing accurate forecasts of hazardous weather associated with landfalling tropical cyclones remains a difficult challenge for tropical meteorologists and operational forecasters. In particular, inland sustained wind speed and gust forecasts are areas with significant opportunity for improvement. While past studies have examined the evolution of the tropical wind field after landfall, the results from these studies have not been routinely used by NWS forecasters in operational prediction. Currently, the National Hurricane Center (NHC) supplies Weather Forecasting Offices (WFOs) with official forecast advisory wind radii. A tool at the local WFOs interpolates these coarse wind radii forecasts to a 5 km x 5 km grid at hourly temporal resolution. Forecasters are then tasked with modifying these grids to account for local effects. As noted by many forecasters in the mid-Atlantic and southeastern region in a recent survey, this modification process is quite subjective and adjustments are often made without strong scientific backing. Strong discontinuities in forecasts from neighboring WFOs often result due to the subjective nature of the forecasting process.

In this study, we aim to improve the currently used methodology for operational forecasts of wind speed and wind gust. In particular, the focuses for the study are improvement in the land decay factor and gust factors applied in the TCMWindTool for various locations and tropical cyclone situations. A climatology of observed wind speed distributions is developed for various locations in the region and compared to distributions for landfalling tropical cyclones. Decay as a system moves over land is also examined for recent tropical cyclones in the region. A systematic verification of recent past forecasts issued by local WFOs, compared to observations as well as the Hurricane Research Division H*Wind products. From here, a statistical-dynamical model of land decay factors and wind gusts will be developed by combining the observed climatology of cases with high-resolution numerical simulations of selected cases.

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