Tuesday, 11 February 2003: 5:00 PM
El NiŅo/Southern Oscillation impacts on peak wind gusts in the United States
Changes in the peak wind gust magnitude are identified over the contiguous United States in association with the warm and cold phases of the El Niņo/Southern Oscillation (ENSO). All calculations of the peak wind gust are differences in the extreme phases of ENSO (warm and cold) relative to neutral for all stations in the study that pass a data completeness criteria. Monthly composites were created for all years in the study (1 January 1955 through 31 August 1998). The differences in the mean peak wind gust are calculated for each month. A non-parametric statistical test is invoked to determine significant shifts in the extreme phase distributions. Differences in the frequency of gale force wind gusts are also calculated. Hypotheses will be presented to relate physical processes associated with ENSO and the observed signals in the study. There is an evident relationship between the influence of the jet stream and the patterns observed in the peak wind gust. The results to be presented include a dominant, ENSO cold phase, wintertime signal. Regions most greatly affected are the Pacific Northwest, Southwest, the Great Plains, and the Ohio River Valley including the Great Lakes and Texas. During the cold phase months from November to March, these regions experience an overall increase in the gustiness of the winds. The warm phase is associated with overall decreased gustiness in the Pacific Northwest during these months; however, the signal is of a lesser magnitude. There is also an observed decrease in the Central Great Plains during the warm phase months of April and June. Potential applications of the results will be discussed.