After an extremely wet summer monsoon in the heart of the rainy season, the rainfall during the 2nd Quarter of 2006 was quite dry, with a 3-month total of 17.88 inches (61%). On average the rainfall at Pago Pago is less than 10 inches in each of the months May through September. April’s 5.15 inches represented an abrupt end to extreme wet conditions in American Samoa, and signaled an early start to the dry season.

Climate Outlook: American Samoa is now entering the heart of its dry season. Earlier computer models (and the official PEAC forecasts as well) indicated rainfall in American Samoa was likely to remain above normal as the island group entered its dry season. This was not the case for April through June as conditions were dry. Long-range computer rainfall forecasts have only limited skill in the tropical Pacific islands, and American Samoa is in a region where the effects of ENSO are more varied than at other locations. However, in July WSO Pago Pago received 8.27 inches (144% of normal) indicating that the dry conditions may be ending. Thus, for this outlook, a forecast based on climatology, persistence, and some computer model input indicates near normal conditions with a normal onset to the next rainy season.

The threat of a damaging tropical cyclone in any of the islands of American Samoa is essentially over until the next rainy season (2006-07). After consultation with American Samoa WSO personnel, we agree that the threat of a damaging tropical cyclone is greatest during weak El Niño conditions. During strong El Niño’s, the cyclone paths shift eastward into French Polynesia, and during La Niña, the cyclones tracks are shifted westward into the Coral Sea. With some climate models indicating a trend toward weak El Niño conditions in the latter half of 2006, there is a possibility of a busy cyclone season.  Normal cyclone activity for an entire rainy season indicates that two or three named tropical cyclonesNormal cyclone activity for an entire rainy season indicates that two or three named tropical cyclones would pass to the south of American Samoa producing episodes of heavy rainfall and gale force northwesterly winds.

Predicted rainfall for American Samoa from July 2006 through June 2007 is: