Session 2.11 Strong wind characteristics and changes during the last half-century at five NWS stations near Coastal South Carolina

Monday, 20 June 2005: 4:30 PM
North & Center Ballroom (Hilton DeSoto)
Allen H. Weber, Savannah River National Laboratory, Aiken, SC; and M. J. Parker and R. L. Buckley

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Strong wind events often have dramatic and long-lasting effects on agriculture, commerce, industry, and infrastructure in the coastal and piedmont areas of South Carolina. The causes of each individual event can vary from tropical weather systems, strong cold fronts, or migratory low pressure systems in winter. In order to better understand the trends associated with strong wind events, five National Weather Service (NWS) stations in the Southeast (Augusta, GA: AGS; Columbia, SC: CAE; Charleston, SC: CHS; Savannah, GA: SAV; and Wilmington, NC: ILM) were selected for analysis for their length of record and completeness during the last half century. The surface wind speed observations from these stations were broken down into ranges from 0-9 mph, 10-25 mph, and greater than 25 mph for further analysis. Air temperatures and dew points associated with this breakdown were also examined.

Strong winds exhibited two trends, first diminishing from 1951 to roughly 1970, followed by an increasing trend to the present time. In addition, wind-temperature-dew point cycles of 2½ to 5 years were manifested in the data. Interestingly, no correlation with NAO and ENSO indices was found. The decade of the 1950s was found to be noticeably more active in terms of strong wind events than the succeeding decades to present.

An examination of the monthly mean winds showed that the maximum mean wind occurs in the months of March and April and is nearly identical for both of these months, whereas the minimum occurs in August. On the other hand, when the wind speeds are restricted to those above 25 mph, the maximum is in August-September whereas the minimum is in May. This indicates the strong influence of tropical weather systems. However, by selecting periods where strong winds occurred for prolonged periods of 5 or more hours, the monthly peak occurs during February and March. These events are caused by migratory low pressure systems and strong cold fronts.

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