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Pacific ENSO Update

1st Quarter, 2011 Vol. 17 No. 1


As mentioned earlier, there was a deep collapse in the number of tropical cyclones in the North Pacific Basin during 2010. Both the western North Pacific and eastern North Pacific cyclone totals were far below normal. The 14 named tropical cyclones that occurred in the western North Pacific was the lowest total in the modern record, which extends back to 1959 (the year that the JTWC was established on Guam). The JTWC numbered 19 tropical cyclones during all of 2010 (a record low). Of these 19 numbered cyclones, 14 were given names by the Japan Meteorological Agency. To qualify for a name, a cyclone must attain at least tropical storm intensity. Tropical depressions with lesser winds may earn number designators from the JTWC, but are not named by the JMA. Of the 19 cyclones numbered by the JTWC, eight were typhoons, six were tropical storms, and five were tropical depressions. On average there are 18 typhoons, 10 tropical storms, and 3 tropical depressions in the western North Pacific. The eastern North Pacific also saw a substantial reduction of tropical cyclone activity. The National Hurricane Center (NHC) in Miami named only 7 cyclones there (a record low). The 2010 cyclone summary for the eastern North Pacific included 3 hurricanes, 4 tropical storms, and 5 tropical depressions. The Central Pacific Hurricane Center in Honolulu had only one cyclone to deal with during 2010. This unusual cyclone (Tropical Storm Omeka) formed late in the year (mid-December) to the west of Hawaii in a relatively rare sub-tropical weather pattern similar to the pattern that spawned Typhoon Dolphin in 2008. Thus, the total number of named tropical cyclones in the North Pacific was 22. This is far below the typical value of approximately 45, and is an unprecedented low value in the modern-day time series, which dates back to 1966 when satellite imagery made counts of cyclones in the eastern North Pacific more reliable. There is currently no generally accepted explanation for the dramatic decline in North Pacific tropical cyclones. Some climate simulations of a warmer world indicate reduced tropical cyclone activity in the Pacific, but given the high activity of the decade of the 1990s followed by the low activity of the 2000s, it is difficult to attribute the recent reduction of activity to global warming.

The PEAC Center archives western North Pacific tropical cyclone numbers, track coordinates, and 1-minute average maximum sustained wind taken from operational warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawai'i. Western North Pacific tropical cyclone names are obtained from warnings issued by the Japan Meteorological Agency (JMA), which is the World Meteorological Organization's Regional Specialized Meteorological Center (RSMC) for the western North Pacific basin. The PEAC archives South Pacific tropical cyclone names, track coordinates, central pressure, and 10-minute average maximum sustained wind estimates from advisories issued by the Tropical Cyclone Warning Centers at Brisbane, Nadi, and Wellington. The numbering scheme and the 1-minute average maximum sustained wind estimates are taken from warnings issued by the JTWC. There are sometimes differences in the statistics (e.g., storm maximum intensity) for a given tropical cyclone among the agencies that are noted in this summary.

Pacific ENSO Applications Climate (PEAC) Center
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Page Last Modified: February 24 2011 06:44:24 GMT


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