Role of the Gulf Stream on Extratropical Cyclogenesis Neil Jacobs, Sethu Raman, and Gary Lackmann Department of Marine, Earth, and Atmospheric Sciences North Carolina State University, Raleigh, NC 27695-8208

Rapidly intensifying coastal storms, sometimes called Nor’easters, develop along the Atlantic states during the fall, winter and spring months. These extratropical cyclones that produce gale force winds, heavy snow, ice, and coastal storm surges with intense beach erosion, are responsible for severe property damage along the eastern seaboard. Several factors are important in the development of an extratropical winter cyclone. Different degrees of storm intensity depend on which factors are present at specific times. A mesoscale model (MM5 – version 3.6) is used in this study to investigate the role of the Gulf Stream sea surface temperatures (SST) and the warm core eddies in the rapid development of the 24-25 January 2000 snowstorm. Leaving all the model parameters with the exception of the SST unchanged, the contribution of insufficient SST data as a possible source of forecast error is isolated. Simulations using the low resolution climatological SST data are compared to simulations initialized with high-resolution SST data. Since the high resolution SST data is not multi-day composite or time averaged, it more accurately represents short-term features such as immediate Gulf Stream front position and quickly moving warm core filaments. The numerical results suggest that the high resolution SST improves the forecasted track and the intensity of the surface low and the model predicted precipitation amounts better over the mid-Atlantic states.