Pacific ENSO Update

3rd Quarter, 2008 Vol. 14 No. 3

FSM Flag Federated States of Micronesia

Pohnpei State: A majority of locations on Pohnpei Island and the atolls of Pohnpei State were very wet (more than 120% of normal) during the first half of 2008, particularly during the 2nd Quarter of the year when some of the April rainfall totals on Pohnpei Island were over 30 inches. The 110.07 inches recorded at the WSO in Kolonia during the first 6 months of 2008 was 122% of its normal. At Palikir, the 116.97 inches for the 1st half of 2008 was the highest value among Pohnpei Island’s coastal stations. The 115.57 inches of rain recorded at Nukuoro during the first half of 2008 was substantially wetter (148%) than normal. Contrary to expectations, the rainfall at Kapingamarangi continues to be wetter than normal, although a period of very dry weather there in March and April brought the 2008 1st half total (60.88 inches) into the near normal category.

Rain gages placed on top of Nahna Laud (the highest mountain in Pohnpei’s rainforest interior) received 103.47 inches in the 2nd Quarter of 2008. Although the rainfall totals for January and February were missing at this site, it is very likely that Nahna Laud topped all stations for the 1st half totals. Since 2003 when the Nahna Laud gages were installed, this site has received an annual average of 330 inches of rain.

Pohnpei Rainfall Summary 2nd Quarter and 1st Half 2008

Station   April May June 2nd Qtr
1st Half
Pohnpei Island
Pohnpei WSO
Rainfall (inches)
29.33
16.28
20.83
66.44
110.07
% of Normal
178%
85%
122%
126%
122%
Palikir
 Rainfall (inches)
38.55
19.29
15.11
57.02
185.27
% of WSO
216%
93%
90%
128%
120%
Kolonia Airport
Rainfall (inches)
24.59
17.94
17.84
60.37
94.74
% of WSO
180%
113%
125%
138%
127%
Nahna Laud*
Rainfall (inches)
39.15
33.63
30.69
103.47
N/A
% of Normal
N/A
N/A
N/A
N/A
N/A
Atolls of Pohnpei State
Nukuoro
 Rainfall (inches)
22.80
14.40
18.77
55.97
115.57
% of Normal
152%
98%
154%
133%
148%
Pingelap
 Rainfall (inches)
24.42
17.04
21.49
62.95
95.33
% of Normal
142%
100%
132%
125%
106%
Mwokilloa
 Rainfall (inches)
13.48
16.45
19.13
49.06
77.46
% of Normal
79%
96%
118%
97%
87%
Kapingamarangi
 Rainfall (inches)
4.73
12.93
17.37
35.03
60.88
% of Normal
35%
125%
240%
112%
93%
* Long term normal is not established for these sites

Climate Outlook: Light easterly winds should continue to dominate the flow in eastern Micronesia for the next few months. This wind pattern should accompany tranquil weather (no unusual extremes of rainfall or high wind). Light wind speeds during August and September should contribute to a sea breeze pattern that features heavy showers or thunderstorms over the rainforest interior during the heat of mid-day, and cool winds off the mountains after the showers dissipate at night. Recent dryness in July should be balanced by near-normal rainfall for the next two or three months. No typhoons or tropical storms are anticipated to adversely affect Pohnpei State during 2008; however, several of the basin’s tropical cyclones may begin as depressions near Pohnpei Island and contribute to the expected near-normal rainfall totals.

Forecast rainfall for Pohnpei State from July 2008 through June 2009 is as follows:

Inclusive Period

% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Pohnpei Islands and Atolls Kapingamarangi
July - September 2008
90%
(43.23 inches)
100%
(22.70 inches)
October - December 2008
 100% 100%
January - March 2009
 100% 100%
April - June 2009
 110% 100%
Forecast rainfall quantities represent BEST ESTIMATES given the probabalistic forecast for each particular season and station.

Source: UOG-WERI