Pacific ENSO Update

4th Quarter, 2007 Vol. 13 No. 4

FSM Flag Federated States of Micronesia

Chuuk State: It was relatively dry throughout most of Chuuk State during the 3rd Quarter of 2007. As at Guam and other locations in the eastern half of Micronesia, the weather was very tranquil: winds were light, there were few instances of rainfall in excess of 2-inches in 24 hours, and no organized tropical cyclones passed through the area. Whereas the normal rainfall throughout Chuuk State for each month at this time of year is over 10 inches, most locations experienced at least one month during the past 3 months with less than 10 inches of rain. At several locations, all three months (July through September) received less than 10 inches apiece. The 3rd Quarter total rainfall of 29.48 inches at the WSO was 77% of the normal. Only Ta, Losap, and Polowat received more rainfall than the WSO during this time period.

Chuuk State Rainfall Summary 3rd Quarter 2007

Station   July Aug. Sept. 3rd Qtr Predicted (3rd Qtr)
Chuuk WSO Rainfall (inches)
10.97
8.84
9.67
29.48
38.29
% of Normal
91%
60%
84%
77%
100%

Piis Panew*

Rainfall (inches)
2.96
7.34
5.95
16.25
38.29
Xavier HS Rainfall (inches)
14.02
9.30
3.12
26.44
38.29

Lukunoch*

 Rainfall (inches)

9.78

5.85
6.70
22.33
38.29
Ettal* Rainfall (inches)
8.25
7.58
10.80
26.63
38.29

Ta*

Rainfall (inches)
8.09
15.47
7.87
31.43
38.29

Fananu*

Rainfall (inches)
4.87
9.36
7.59
21.82
36.38
Onoun* Rainfall (inches)
7.19
4.73
14.54
26.46
36.38

Losap*

Rainfall (inches)
10.66
11.22
16.69
38.57
38.29

Nama*

Rainfall (inches)
8.23
5.92
11.05
25.20
38.29

Polowat

Rainfall (inches)
6.67
17.35
5.81
29.83
38.29
Predicted rainfall refers to forecast made in 2nd Quarter 2007 PEAC Newsletter.
* Long term normal is not established for these sites
** Estimated

Climate Outlook: The threat of a direct strike by a strong tropical storm or typhoon on any of the islands of Chuuk State should remain below normal for the remainder of 2007. Because of La Niña-related weather patterns, any tropical systems that form near Chuuk in the next three months will likely be in their disturbance state of development, and only become tropical storms after passing out of Chuuk State. Some heavy rainfall events (more than 2 inches of rainfall in one day) may occur in the next three months in association with tropical disturbances in the area. Overall, however, rainfall at most locations within Chuuk State should be near normal for at least the next three months.

Based on a continuation of La Niña conditions during the first few months of 2008, rainfall at islands and atolls of the Chuuk Lagoon and on the other atolls of Chuuk State could become wetter than normal in the spring (late March through early June) when the trade-wind trough becomes established in the region.

Forecast rainfall for Chuuk State from November 2007 through October 2008 is as follows:

Inclusive Period
% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Chuuk Lagoon, and Northern Mortlocks
Polowat
Northern Atolls

Southern
Mortlocks
Nov - Dec 2007
100%
(21.55 inches)
100%
(21.55 inches)
100%
(21.55 inches)
100%
(21.55 inches)
Jan - March 2008
100%
95%
95%
110%
Apr - June 2008
110%
100%
100%
120%
July - Oct 2008
100%
100%
100%
100%
Forecast rainfall quantities represent BEST ESTIMATES given the probabalistic forecast for each particular season and station.

source: UOG-WERI