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Pacific ENSO Update

1st Quarter, 2012 Vol. 18 No. 1


During 2011, tropical cyclone activity recovered somewhat in both the western North Pacific and eastern North Pacific from the extreme quiescence seen in both basins during 2010. The 2011 activity, however, was still well below normal in both basins with the JMA naming a total of 21 tropical cyclones (75%) in the western North Pacific, and the National Hurricane Center, Miami, naming 11 tropical cyclones (69%) in the eastern North Pacific. The JTWC numbered a total of 27 tropical cyclones, of which seven reached only tropical depression (TD) status (i.e., peak winds less than gale force). Only one of the seven JTWC TDs was given a name by the JMA (JTWC = TD 09W, JMA = Tropical Storm Tokage). There were only 10 typhoons (58%) in the western North Pacific, but 10 of the 11 named cyclones in the eastern North Pacific became hurricanes, which is a normal number of hurricanes, but an unusual proportion of hurricanes to the total number of named cyclones. The Central Pacific Hurricane Center in Honolulu did not name any tropical cyclones during 2011. The low tropical cyclone activity of 2011 continues a decade-long lull in basin and global tropical cyclone activity. 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 and most other global basins, but given the high activity of the decade of the 1990s, it is difficult to attribute the recent abrupt 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.

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Page Last Modified: March 22 2012 05:05:13 GMT


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