26th Conference on Hurricanes and Tropical Meteorology


ENSO and NAO signals on the Isthmus of Tehuantepec winds

Rosario Romero-Centeno, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico; and J. Zavala-Hidalgo and G. B. Raga

Different data sources (NCDC, NCEP, direct wind and sea level pressure measurements) are used to study the statistical characteristics of the winds at the Isthmus of Tehuantepec and their seasonal and interannual variability. Observations show that the long-term monthly mean wind speeds and frequency of occurrence of northerly winds have a strong seasonal signal, with maximum values during December-January, minimum during May-June and a relative maximum in July. The frequency distribution of wind speed is bimodal, a feature that is closely related to the wind direction, with northerly winds being stronger. Based on these results and in the close relationship between the across-Isthmus pressure differences and the local winds, a statistical model is developed to get a reconstruction of 12 hourly winds through the Isthmus of Tehuantepec for 1964-1995. The model reproduces fairly well the main characteristics of the observed winds. Reconstructed winds show that the high frequency of northerly winds in July is associated with weaker winds than those observed in winter. The summer maximum seems to be related with the westward displacement and strengthening of the Bermuda high during this time of the year. Based on the model results, the long-term monthly mean wind speeds and percentage of occurrence of northerly winds show larger values during El Niņo years compared with La Niņa years. Also, the influence of the NAO on the interannual variability of the mean wind speed and the frequency of occurrence of northerly winds is analyzed.

extended abstract  Extended Abstract (360K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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