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Pacific ENSO Update

4th Quarter, 2012 Vol. 18 No. 4


FSM Flag Federated States of Micronesia

Yap State: All locations on Yap Island were very wet during the 3 rd Quarter of 2012, with the very heavy rainfall of August and September, more than compensating for the somewhat dry conditions during July. Rainfall totals in excess of 25 inches occurred during September at several Yap Island locations. This represented almost twice the normal rainfall for that month. Yap Island was embedded in monsoon flow for most of the 3 rd Quarter. Several of the basin’s tropical cyclones passed well to the north of Yap, but they served to anchor and enhance the deep southwesterly flow over the island, with its embedded showers, squalls and thunderstorms. The monsoon flow persisted on Yap Island through mid-October, and then, as at Guam and in the CNMI, light trade winds became established, and heavy shower activity eased. The weather at Ulithi (located about 130 miles to the northeast of Yap Island) was also wet during the 3 rd Quarter, with its 3-month total of 49.47 inches 135% of average. In the southeastern portion of Yap State, the island of Woleai (located about 390 miles southeast of Yap) was much drier, with a 3 rd Quarter total of only 25.35 inches (63%). This is plausible, since the monsoon trough and monsoon cloud band was located well to the north of this location, as a weak ridge of high pressure built in over the Island from the east, southeast of the monsoon band.

Yap State Rainfall Summary 3rd Quarter 2012

Station   Jul. Aug. Sep. 3rd Qtr
Predicted
Yap Island
Yap WSO
Rainfall (inches)
12.74
18.92
25.19
56.85
43.25
% of Normal
88%
124%
186%
131%
100%
Dugor
Rainfall (inches)
13.82
20.03
26.73
60.58
43.25
% of WSO
95%
132%
197%
140%
100%
Gilman
Rainfall (inches)
10.19
22.11
22.70
55.00
43.25
% of WSO
70%
145%
168%
127%
100%
Luweech
Rainfall (inches)
12.98
23.41
25.01
61.40
43.25
% of WSO
89%
154%
185%
142%
100%
Maap
Rainfall (inches)
11.00
16.30
28.25
55.55
43.25
% of WSO
76%
107%
209%
128%
100%
North Fanif
Rainfall (inches)
14.40
24.10
26.33
64.83
43.25
% of WSO
99%
159%
195%
150%
100%
Rumung
Rainfall (inches)
9.22
14.32
24.54
48.08
43.25
% of WSO
63%
94%
182%
111%
100%
Tamil
Rainfall (inches)
17.53
14.29
20.13
51.95
43.25
% of WSO
121%
94%
149%
120%
100%
Outer Islands
Ulithi
Rainfall (inches)
17.19
19.30
12.98
49.47
36.76
% of Normal
139%
149%
113%
135%
100%
Woleai
Rainfall (inches)
10.93
6.59
7.83
25.35
40.30
% of Normal
78%
45%
67%
63%
100%
Predictions made in 2nd Quarter 2012 Pacifc ENSO Update newsletter.

Climate Outlook: El Niño typically has a high risk of producing very dry conditions during the first 6-months of the year (i.e., January through June) that follows a moderate or strong El Niño event. The dryness is exacerbated in two ways: (1) a reduction in the monthly values of rainfall; and (2) an extension of the dry season into June and July. Because we are now only at the borderline of El Niño and it is very late in the year, if an El Niño were to develop, it is not likely to have a big effect on the rainfall or tropical cyclone activity. Yap can expect its normal dry season rainfall. Even in ENSO-neutral conditions, there is a normal risk (roughly a 10-15% chance) of a damaging tropical cyclone affecting any of the islands of Yap State during November and December. An extreme drought of the magnitude that occurred during the first half of 1983 or of 1998 is not anticipated. Most tropical cyclones affecting Yap State form near Chuuk or Guam and pass to the north of Yap Island. The two most recent typhoons affecting Yap State during El Niño were Mitag and Sudal. These occurred during the spring months of March 2002 and April 2004, respectively.

Predicted rainfall for Yap State from October 2012 through September 2013 is as follows:

Inclusive Period
% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Yap and Ulithi
Woleai
October - December 2012
(End of Rainy Season)
100%
(30.41 inches)
100%
(36.36 inches)
January - March 2013
(Heart of Next Dry Season)
80% 90%
April - June 2013
(Onset of Next Rainy Season)
85% 90%
July - September 2013
(Heart of Next Rainy Season)
100% 100%

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

source: UOG-WERI



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Web Master's email: peac@noaa.gov
Page Last Modified: January 15 2013 03:50:04 GMT

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