84th AMS Annual Meeting

Wednesday, 14 January 2004
Scatterometer Inferred Winds in the Vicinity of the Gulf Stream
Hall AB
Joseph M. Sienkiewicz, NOAA/NWS/NCEP, Camp Springs, MD
Poster PDF (2.5 MB)
The NOAA/NWS Ocean Prediction Center (OPC) is responsible for issuing warnings and forecasts for winds and waves over the Offshore and High Seas waters of the Northeastern and Mid-Atlantic Coasts of the United States. These waters contain complex sea surface temperature gradients associated with the slope, shelf and Gulf Stream waters.

Scatterometer inferred winds from the NASA QuikSCAT satellite aid OPC forecasters in the warning and forecast decision process. The QuikSCAT winds are fully integrated into OPC operations. Forecasters have the ability to display QuikSCAT winds on their operational workstations and overlay them with a variety of other data sets including; model forecast fields, satellite imagery, conventional observations, and sea surface temperature analyses. As a result, forecasters have observed wind speed gradients across areas of large sea surface temperature gradients.

Examples of QuikSCAT winds across the sea surface temperature gradients of the Gulf Stream, slope, and shelf waters will be shown. In general, a 40 to 50% reduction in wind speed has been observed in southerly flow over the colder slope waters as compared to the warmer Gulf Stream waters. Numerical forecast guidance winds typically under forecast wind speed over the warmer waters and significantly over forecast wind speeds over the cooler waters. A direct result is that numerical wave models over forecast seas over the cool waters and under forecast seas over the warmer waters. Several examples will be shown. The inability to accurately forecast the winds is likely due to poor resolution of SST gradients in numerical guidance and an inability to simulate changes in boundary layer stability across these SST gradients. Examples of stability indices and wind guidance used by OPC forecasters will be shown. This study emphasizes the need for accurate and timely SST analyses and improved boundary layer resolution.

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