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Pacific ENSO Update

2nd Quarter, 2011 Vol. 17 No. 2


FSM Flag Federated States of Micronesia
Yap State: Rainfall during the first three months of 2011 was above normal throughout most of Yap State. Yap Island was wettest with roughly 30 inches of rain during the 1st quarter, or 150% of normal. At some of the atolls of Yap State it was drier. Ulithi’s 17.73 inches of rain during the 1st Quarter was 108% of normal, and the 3-month total of 18.17 inches at Woleai was only 69% of normal. In a La Niña weather pattern, the heavy rainfall of the tropical western North Pacific shifts to the west (or at least is not reduced in the western portion of the basin). Located in the western portion of Micronesia, there has been an abundance of convective cloud clusters and tropical disturbances providing heavy rainfall in Yap State. At the end of March, a large monsoon depression formed near Yap and Palau. This monsoon depression evolved into Tropical Depression 02W. The monsoon depression and the numbered tropical depression that it spawned, stayed in the region of Yap State for over a week. Abundant rains, a period of westerly wind, and some high surf on the western shores were their affects in Yap State.

Yap State Rainfall Summary 1st Quarter 2011

Station   Jan. Feb. Mar. 1st Qtr
Predicted
Yap Island
Yap WSO
Rainfall (inches)
11.80
6.71
10.50
29.01
19.27
% of Normal
161%
112%
176%
151%
100%
Dugor
Rainfall (inches)
10.75
9.94
11.90
32.59
19.27
% of WSO
147%
166%
200%
169%
100%
Gilman
Rainfall (inches)
14.75
5.94
11.02
31.72
19.27
% of WSO
201%
99%
185%
165%
100%
Luweech
Rainfall (inches)
13.36
4.34
10.86
28.56
19.27
% of WSO
182%
73%
182%
148%
100%
Maap
Rainfall (inches)
11.32
7.40
9.10
27.82
19.27
% of WSO
154%
124%
153%
144%
100%
North Fanif
Rainfall (inches)
13.67
9.88
10.17
33.72
19.27
% of WSO
186%
165%
171%
175%
100%
Rumung
Rainfall (inches)
11.04
9.87
8.80
29.71
19.27
% of WSO
151%
165%
148%
154%
100%
Tamil
Rainfall (inches)
14.45
8.88
9.08
32.41
19.27
% of WSO
197%
148%
152%
168%
100%
Outer Islands
Ulithi
Rainfall (inches)
5.30
4.98
7.45
17.73
16.38
% of Normal
85%
98%
147%
108%
100%
Woleai
Rainfall (inches)
3.25
6.91
8.01
18.17
26.48
% of Normal
30%
92%
97%
69%
100%
Predictions for 1st Quarter 2011 made in 4th Quarter 2010 Pacifc ENSO Update newsletter.

Climate Outlook: Computer forecasts and a consensus of outlooks from several regional meteorological centers indicate that rainfall throughout Yap State is likely to be slightly above normal for at least the next few months as the rainy season becomes established. Normal monthly rainfall on Yap Island begins to top 10 inches starting in June, but it is likely that April and May will each exceed 10 inches in the current weather pattern. Abundant rainfall is anticipated to occur throughout Yap State for the foreseeable future.

There is a normal risk (roughly a 10-15% chance – that is, once in 7 to 10 years) of a damaging tropical cyclone in Yap State or its outer atolls during 2011 . Most tropical cyclones affecting Yap State form near Chuuk or Guam and pass to the north of Yap Island. The northern atolls of Yap State (e.g., Ulithi and Fais) are probably most vulnerable to typhoons, but two recent typhoons (Mitag – March 2002, and Sudal – April 2004) made direct hits on Yap Island.

Predicted rainfall for Yap State from April 2011 through March 2012 is as follows:

Inclusive Period
% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Yap and Ulithi
Woleai
April - June 2011
(Onset of Rainy Season)
120%
(32.63 inches)
100%
(36.26 inches)
July - September 2011
(Heart of Rainy Season)
100% 100%
October - December 2011
(End of Rainy Season)
120% 100%
January - March 2012
(Heart of Next Dry Season)
110% 100%

Forecast rainfall quantities represent BEST ESTIMATES given the probabalistic forecast for each particular season and station.

source: UOG-WERI



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Page Last Modified: May 21 2011 01:25:25 GMT

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