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The PEAC tropical cyclone outlook for the upcoming typhoon season of 2009 is for more activity in the western North Pacific basin than occurred there in 2008, even though the typhoon season may once again start get off to a late start because of La Niña conditions in the basin. Also, the geographical distribution of western North Pacific tropical cyclones should return to a more normal pattern, elevating the risk of a typhoon in Micronesia (from Chuuk and westward) to near normal. Islands from Pohnpei and eastward into the RMI experience tropical storms and typhoons primarily during El Niño. The risk of a damaging tropical cyclone in these locations is considered low during 2009 (but not quite so extraordinarily low as it was in 2007 and 2008).

The 2008-2009 South Pacific hurricane season is off to a relatively slow start. There has been only one cyclone (Charlotte) named by the responsible agencies in this basin from July 2008 through mid-January 2009. Although only one cyclone has been named in the South Pacific basin, an active monsoonal cloud band with embedded cyclonic disturbances contributed to severe flooding in Fiji in early January. The focus of tropical cyclone and monsoonal activity in the South Pacific has been between northeastern Australia and Fiji, with one episode of northwest monsoonal winds reaching the islands of American Samoa. This is typical of La Niña conditions. In ENSO-neutral years, the tropical cyclone activity of the South Pacific is more likely to extend eastward to the region of Samoa, or in the case of El Niño years, reach as far east as the Cook Islands and French Polynesia. The activity occurs further eastward in rough proportion to the strength of El Niño and further westward in rough proportion to the strength of La Niña.

The PEAC Center remains cautiously optimistic that the primary focus of South Pacific tropical cyclone activity will, for the next three months, remain in the Coral Sea from northeastern Australia eastward to Fiji, a view also supported by the TSR research group (see excerpt below). Through April 2009, it is likely that 1 or 2 tropical cyclones will pass close enough to American Samoa to bring gusty northwesterly winds of near-gale strength to the islands and territorial waters. The risk of a damaging impact by a hurricane or strong tropical storm in American Samoa is considered to be near normal (roughly a 5% - 10% chance) through April 2009. For comparison, the risk of a damaging impact by a typhoon on Guam is typically 15 - 20% during any given year, increasing to 30% - 40% during El Niño years.

On December 4, 2008, the Tropical Storm Risk (TSR) Research Group issued the following assessment of tropical cyclone activity for the Australian region:  

“The TSR early December forecast update for Australian-region tropical cyclone activity in 2008/9 anticipates activity approximately 10% above the 1975/6-2007/8 climate norm. The forecast spans the Australian season from the 1st November 2008 to the 30th April 2009 and is based on data available through the end of November 2008. Our main predictor is the observed anomaly in October-November Niño 4 sea surface temperatures (SST) which is below average at -0.5°C. … Thus we expect Australian basin cyclone activity and landfalling numbers to be above-average in 2008/9.”

“Our Australian-region (100°E to 170°E), while slightly non-standard, is selected to provide the best overview for tropical cyclone activity around the whole of Australia.

There is a 45% probability that Australian-region tropical storm numbers in 2008/9 will be above average (defined as more than 12 tropical storms), a 45% likelihood they will be near normal (defined as between 9 and 12 tropical storms) and only a 10% chance they will be below normal (defined as less than 9 tropical storms). …”

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The PEAC forecast considers input from two seasonal outlooks for tropical cyclone activity in the western North Pacific basin: (1) The City University of Hong Kong Laboratory for Atmospheric Research, under the direction of Dr. J. C-L. Chan, and, (2) The Benfield Hazard Research Centre Tropical Storm Risk (TSR) Research Group at University College London, UK, led by Dr Adam Lea and Professor Mark Saunders.