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Pacific ENSO Update

4th Quarter, 2009 Vol. 15 No. 4


Guam and CNMI text Guam/CNMI:  The 3rd Quarter of 2009 was wetter than normal throughout Guam and the CNMI. August was particularly wet, with recorded rain totals on Guam reaching nearly 30 inches, which was twice the monthly normal. An active monsoon was responsible for several episodes of heavy daily rainfall. Various stations recorded 5- inch rainfall totals on three separate days within the first week of August. During September, the rainfall was also above normal, but not quite as heavy as during August. Several tropical cyclones passed by Guam, but not in close enough proximity to produce any significant winds. Due to wet conditions in July and August, CNMI rainfall was above normal during for the 3rd Quarter. As on Guam, a wet August was responsible for most of the surplus. Typhoon Choi-Wan passed directly over Alamagan on the afternoon of 15 September. The island was heavily damaged by the near super typhoon’s sustained 125 kt winds which mangled vegetation and totally destroyed the few homes in a small settlement on the northwest coast of the island. A news item on the website of the Pacific Disaster Center shows dramatic pictures of the island after the typhoon.

On the 3rd of October, another typhoon passed through the CNMI: Typhoon Melor (20W). This typhoon produced storm-force winds on the island of Saipan with some minor wind damage reported (e.g., a few trees uprooted), and accompanied by high surf. Tropical Cyclone Lupit (22 W) passed to the south of Guam on the 15th of October. A squall associated with this cyclone passage caused wind gusts to near 60 mph, but only minor damage to foliage was reported.

Guam and CNMI Rainfall Summary 3rd Quarter 2009

Station   Jul. Aug. Sep. 3rd Qtr
Predicted
Guam
Guam Intl. Airport (WFO)
Rainfall (inches)
10.72
26.14
15.54
52.40
33.98
% of Normal
102%
190%
115%
139%
90%
Anderson AFB
Rainfall (inches)
10.26
21.42
11.76
43.44
33.98
% of Normal
94%
160%
88%
115%
90%
University of Guam
Rainfall (inches)
2.04
1.77
5.43
9.24
33.98
% of Normal
52%
29%
84%
56%
90%
Dedado (Ypapao)*
Rainfall (inches)
13.78
27.33
17.33
58.44
33.98
% of AAFB
126%
204%
130%
155%
90%
Ugum Watershed **
Rainfall (inches)
10.13
23.61
16.49
50.23
33.98
% of WSMO
96%
172%
122%
133%
90%
Sinajaña***
Rainfall (inches)
13.47
28.90
15.33
57.70
33.98
% of WFO
128%
210%
114%
153%
90%
Commonwealth of the Northern Mariana Islands
Saipan Intl. Airport
Rainfall (inches)
10.95
14.64
12.09
37.68
31.80
% of Normal
135%
117%
90%
110%
95%
Capital Hill
Rainfall (inches)
12.27
18.39
10.72
41.38
33.39
% of Normal
136%
147%
79%
118%
95%
Tinian Airport
Rainfall (inches)
11.05
11.95
13.19
36.19
33.41
% of Normal
123%
96%
98%
106%
95%
Rota Airport
Rainfall (inches)
10.89
17.35
12.70
40.94
35.21
% of Normal
104%
132%
95%
111%
95%
Predictions made in 2nd Quarter 2009 Pacifc ENSO Update newsletter.
* % of normal for Dededo is with respect to AAFB.
** % of normal for Ugum is with respect to WSMO Finigayan (now closed).
*** % of normal for Sinajaña is with respect to WFO Tiyan (GIA).

Climate Outlook: With El Niño conditions substantially increasing the risk of a damaging typhoon on Guam and in the CNMI, the odds of this type of event are roughly 1-in-4, or 25%, from late October through January 2010. For this time period, Guam and the CNMI face the possibility of two or three tropical cyclones passing within 200 miles.

Rainfall is anticipated to be near normal to slightly below normal for Guam and the CNMI for the remainder of 2009 (unless a typhoon brings an extreme daily rainfall value) and to fall below normal during the first half of 2010. A strong El Niño extends the normal dry season and brings very dry conditions to Guam and the CNMI in the winter and spring of the year that follows; however it is not anticipated that the upcoming dry season will be as dry as during 1983 or 1998. Guam can withstand several months of very dry weather, but CNMI has to go through considerable conservation efforts.

Predicted rainfall for Guam and the Mariana Islands from October 2009 through September 2010 is as follows:

Inclusive Period

% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Guam/Rota
Saipan/Tinian
October – December 2009
(End of Rainy Season)
100%
(25.63 inches)
100%
(22.06 inches)
January – March 2010
(Onset of Next Dry Season)
80%
70%
April – June 2010
(End of Next Dry Season)
85%
80%
July– September 2010
(Next Rainy Season)
90%
95%

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

source: UOG-WERI



Pacific ENSO Applications Climate (PEAC) Center
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Web Master's email: peac@noaa.gov
Page Last Modified: June 01 2010 21:07:56 GMT

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