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Pacific ENSO Update

2nd Quarter, 2010 Vol. 16 No. 2


For the third year in a row, the tropical cyclone season in the western North Pacific basin was below normal in almost every category of activity (e.g., number of typhoons). The JTWC numbered 29 tropical cyclones in the western North Pacific basin during 2009, which was 2 below average. Of these 29 cyclones, 4 were tropical depressions, 11 were tropical storms, and 14 were typhoons. The normal values for these statistics are 3, 10, and 18, respectively. Tropical cyclone activity in the western North Pacific basin shifted eastward during 2009, which is typical during an El Niño. Because of this major shift of basin cyclone activity, Micronesia was traversed by several tropical cyclones during 2009. On the evening of September 15, 2009, the center of Typhoon Choi-Wan passed directly over Alamagan with maximum sustained winds of 145 mph. Vegetation was heavily damaged and homes were leveled. Following the aftermath of Super Typhoon Choi-Wan, the USNS Alan Shepard (T-AKE 3) and two MH-60S helicopters from Helicopter Sea Combat Squadron (HSC) 25 arrived on site in the early morning hours of Sept. 17 to provide humanitarian support to residents of Alamagan and Agrihan. One family was transported to Saipan for medical needs. A healthy baby had been born on the island days before the storm’s arrival, and the child was in good condition.

The Southern Hemisphere TC season of 2009-2010 saw below average numbers of cyclones with a shift to the east of cyclone activity. Through mid-April 2010, the JTWC had numbered 23 cyclones in the Southern Hemisphere, which is below the average of 28. During February and early March, the activity shifted eastward into French Polynesia. American Samoa was affected by several cyclones, and on the 12th of February, 2010, one of these cyclones (Rene) passed close enough to the islands of American Samoa to cause flooding and some moderate wind damage. On the island group of Manu’a, strong winds damaged some homes and uprooted banana and breadfruit trees. One casualty was reported during the storm: a man fell off a roof while boarding windows for the winds.

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, Hawaii. Western North Pacific tropical cyclone names are obtained from warnings issued by the Japan Meteorology Agency (JMA), which is the World Meteorological Organization's Regional Specialized Meteorological Center (RSMC) for the western North Pacific basin. The PEAC Center 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, but the JTWC values are given precendence when available.

Pacific ENSO Applications Climate (PEAC) Center
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Page Last Modified: May 29 2010 00:09:19 GMT


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