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Pacific ENSO Update

4th Quarter, 2010 Vol. 16 No. 4


TROPICAL CYCLONE SUMMARY

In contrast to a very active Atlantic, the tropical cyclone activity across the Pacific basin was substantially reduced during 2010. The TC activity in the western North Pacific basin has been flirting all year with record low values. By mid-October, the JTWC had numbered only 15 tropical cyclones. Cyclone number 15 (Super typhoon Megi) was given its number by the JTWC on the morning of 13 October 2010. This was the latest in the records of the JTWC for the formation of the 15th TC of the year. Through 15 October 2010, the JTWC numbered 15 tropical cyclones with the following distribution: seven typhoons, six tropical storms, and two tropical depressions. This is far below normal in all categories. The following experimental forecast for the annual total of western North Pacific TC activity was issued by Paul Stanko (Senior forecaster, Guam WFO) on 10 October 2010:

“The regression forecast [for the 2010 annual total] has slipped to 22 (was 23 in mid-September). This is in the Far Below Normal quintile, and only 1 above the record low. It is also the lowest my forecast has ever issued on this date in all the 52 years of data.

Climatology is 31, so this is 71% of normal, or about 1.7 standard deviations below normal. The R2 value is 0.82 for the regression on this date. Using the training set as well as the operational forecasts for error bar data, here is the category probabilistic forecast, the highlights of which are that we can now exclude a Near Normal season, and the chance of a Record Low season has surged: Record High (45 or more tropical cyclones): 0% (was 0% 20 days ago), Far Above Normal (38 to 44 tropical cyclones): 0% (was 0% 20 days ago), Above Normal (33 to 37 tropical cyclones): 0% (was 0% 20 days ago, Near Normal (29 to 32 tropical cyclones): 0% (was 2% 20 days ago), Below Normal (27 or 28 tropical cyclones): 2% (was 7% 20 days ago), Far Below Normal (21 to 26 tropical cyclones): 67% (was 73% 20 days ago), Record Low (20 or fewer tropical cyclones): 31% (was 18% 20 days ago)”

Tropical cyclone activity is normally reduced in the year that follows El Niño, and 2010 was no exception. The extreme reduction of the inactivity, however, was unusual, and follows a string of recent years (e.g., 2007 and 2008) with low activity. A recent posting (October 10, 2010) by Ryan Maue (http://www.coaps.fsu.edu/~maue/tropical/) details the unusual lack of global TC activity:

“Update: Current Year-to-Date [10 October 2010] analysis of Northern Hemisphere and Global Tropical Cyclone Accumulated Cyclone Energy (ACE) and Power Dissipation Index (PDI) has fallen even further than during the previous 3-years. The global activity is at 33-year lows and at a historical record low where Typhoons form in the Western Pacific. …

While the North Atlantic has seen 15 tropical storms/hurricanes of various intensity, the Pacific basin as a whole is at historical lows! In the Western North Pacific stretching from Guam to Japan and the Philippines and China, the current ACE value of 58 is the lowest seen since reliable records became available (1945) and is 78% below normal. The next lowest was an ACE of 78 in 1998.”

The tropical cyclone activity of the central and eastern North Pacific has also been exceptionally quiet during 2010. Through mid-October, there have been 12 numbered tropical cyclones in the eastern North Pacific. These include only seven named storms. There have been no numbered or named TCs in the central Pacific, and no eastern Pacific tropical cyclone has moved into the central Pacific from the eastern Pacific.

No heavily populated island has yet been severely affected by a typhoon. Some welcome rainfall has fallen recently on Guam and in the CNMI from the passage over those islands of the tropical disturbances that became typhoons Megi and Chaba. See the individual island summaries for more details on tropical cyclone threats.


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: August 04 2011 22:17:16 GMT

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