Pacific ENSO Update

3rd Quarter, 2007 Vol. 13 No. 3

American Samoa: Rainfall for the 2nd quarter of 2007 alternated from very dry conditions in April, to above-normal rainfall in May, and back to drier conditions in June. In April, Pago Pago recorded 42% of normal rainfall while Aasufou received 62% of normal rainfall. May was considerably wetter for both locations, with 166% of normal rainfall at Pago Pago International Airport and 148% of normal at Aasufou. June marked a return to dry conditions for Pago Pago with 58% of normal rainfall, while Aasufou received near normal rainfall for the month. Although American Samoa received an abundant amount of rainfall in May, there were no recorded flood advisories, warnings or any damages reported. The six month total of 127.38 inches at Aasufou was the highest value received by the PEAC for any U.S. Affiliated Pacific Island Station. — WSO Pago Pago

American Samoa Rainfall Summary 2nd Quarter 2007
Station   Apr. May June 2nd Qtr
Predicted (2nd Qtr)
1st Half 2007
Pago Pago WSO
Rainfall (inches)
4.66
17.34
3.44
25.44
24.78
77.11
% of Normal
42%
166%
58%
92%
90%
117%
Aasufou
Rainfall (inches)
11.22
22.67
11.59
45.48
39.36
127.38
% of Normal
62%
148%
102%
104%
90%
129%
Predicted rainfall refers to forecast made in 1st Quarter 2007 PEAC Newsletter.

Climate Outlook: American Samoa is now entering the heart of its next dry season (July to September 2007). With forecast models favoring ENSO-neutral conditions for the next 1-3 months, American Samoa should experience near normal rainfall conditions for the 3rd quarter.

Given the time of year and current status of ENSO, there is no threat of a damaging tropical cyclone affecting any of the Samoan Islands at least until after the onset of the next rainy season.

Forecast rainfall for American Samoa from August 2007 through July 2008 is as follows:





Inclusive Period

% of Long-Term Average Rainfall /
Forecast Rainfall (inches)

August - October 2007
(Heart of Next Dry Season)
95%
(23.00 inches - Pago Pago)
November 2007 – January 2008
(Onset of Next Rainy Season)
95%
February – April 2008
(Heart of Next Rainy Season)
100%
May – July 2008
(Onset of Next Dry Season)
100%
Forecast rainfall quantities represent BEST ESTIMATES given the probabalistic forecast for each particular season and station.

source: UOG-WERI