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Pacific ENSO Update

3rd Quarter, 2011 Vol. 17 No. 3


Tropical cyclone activity in the western North Pacific rebounded during the first half of 2011, with nine JTWC-numbered and seven JMA-named cyclones through mid-July. By contrast, there were only four JTWC-numbered and three JMA-named tropical cyclones through 01 August 2010. Normal tropical cyclone activity through mid-July is approximately eight numbered by the JTWC. Much of the activity has still been shifted to the west, but in a sign of a change from last year’s weather patterns, there was one major typhoon (Ma-on, 08W) occurring during mid-July which was named east of the latitude of Guam in mid-July. The southwest monsoon swept across Palau, Yap State, the CNMI and Guam for several days (12-15 July) as this typhoon passed to the north. The periphery of Typhoon Ma-on and its associated monsoon tail produced spectacular lightning, high surf and localized very heavy rainfall (e.g. 3.37 inches of rain fell at the WSO Guam during a 24-hour period spanning 14-15 July) in Guam and the CNMI.

The Southern Hemisphere cyclone season of 2010-2011 was well below average in most categories of activity. The Southern Hemisphere’s Accumulated Cyclone Energy (ACE) (see for the year ending 30 June 2011 was 140.4 versus a normal of 210, or 67% of normal. The JTWC numbered only 21 tropical cyclones for the South Indian Ocean and South Pacific ocean combined, versus a normal of 28. Tropical cyclone warning agencies in the Southern Hemisphere named only 18 of these, with the RSMC Nadi (Fiji) naming five, the three Tropical Cyclone Warning Centers (TCWCs) of Australia naming nine, TCWC Jakarta (Indonesia) naming one, and RSMC La Reunion naming only three in its area of responsibility in the South Indian Ocean.

The PEAC 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 pressures, 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: August 05 2011 22:59:02 GMT


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