American Samoa:  Month-to-month variability of rainfall was very high during 2007. At Pago Pago, four months received less than 75% of normal rainfall and five months had rainfall at or above 150% of normal. The 2007 annual total rainfall of 145.04 inches at Pago Pago was 122% of its normal value. The highest recorded annual rainfall total in any of the USAPI was the 221.98 inches at A‘asufou. Though very wet, this enormous rainfall total was only moderately above (115%) the normal annual value of 193.05 inches at this location.

American Samoa Rainfall Summary 4th Quarter 2007

Climate Outlook: American Samoa is now within the heart of its rainy season, and nearly all climate models favor a continuation of wetter than normal conditions for at least the next 3 months. Thereafter, as American Samoa enters its typical dry season, the rainfall should return to near normal. Rainfall in American Samoa during past La Niña years of similar strength has been below normal at the end of the dry season into the start of the next rainy season (see the forecasts below).

There has been some concern that above average SST in the vicinity of American Samoa would translate into an increased risk of a damaging tropical cyclone there. Through mid-January, however, tropical cyclone activity has been focused westward and southwestward of there. The PEAC Center remains cautiously optimistic that the focus of South Pacific tropical cyclone activity will remain in the Coral Sea from northeastern Australia eastward to Fiji (see previous tropical cyclone section). Through April 2008, it is likely that one or two tropical cyclones will pass close enough to American Samoa to bring gusty northwesterly winds to near-gale strength at exposed locations and across territorial waters. During this time period, MJO enhancements to the monsoon will bring two or three prolonged (3- to 5-day) episodes of gusty (20-25 kt) northwest wind, with or without the help of a tropical cyclone. 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 to 10% chance) through April 2008.

Forecast rainfall for American Samoa from February 2008 through January 2009 is as follows:

source: UOG-WERI