A new NOAA definition of El Niño identifies a number of additional El Niño seasons beyond those conventionally agreed. These additional seasons are characterized by SST anomalies primarily in the western central equatorial Pacific. We show here that the seasonal weather anomalies over the U.S. associated with these additional Dateline El Niño seasons are substantially different from those associated with conventional El Niño seasons. Although some regions have similar associated anomalies, most of the major regional anomalies are quite different. Treating the two as a single phenomenon yields weaker overall seasonal weather associations and does not take advantage of the stronger associations available when the two are treated separately.

[1] One of the consequences of the new NOAA definition of El Niño is the identification of a number of boreal autumns and winters as El Niño seasons that are not conventionally so identified. In these periods SST anomalies are concentrated significantly more toward the International Dateline than usual. We show here that the seasonal weather anomalies typically associated with these additional ''Dateline El Niño'' seasons are different in useful respects over much of the world, and suggest that it is useful to treat these as different types of ''El Niño'' for purposes of seasonal weather forecasting. Citation: Larkin, N. K., and D. E. Harrison (2005), Global seasonal temperature and precipitation anomalies during El Niño autumn and winter, Geophys. Res. Lett., 32, L16705,

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