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Pacific ENSO Update

2nd Quarter, 2012 Vol. 18 No. 2


Guam and CNMI text Guam/CNMI: The weather during the 1st Quarter of 2012 was very quiet across Guam and the CNMI. Thanks to a wet January on Guam and a wet February on Saipan, the 1st Quarter rainfall totals were above normal at most Guam and CNMI locations. Some locations in the region, however, were drier than normal, including Andersen AFB (Guam), Capitol Hill (Saipan) and the weather station at the Rota Airport. Extended periods of dry weather in mid-March and again in the first two weeks of April caused the vegetation in the grasslands of central and southern Guam to wilt and turn brown. Several brush fires scorched some of the grassland areas of central and southern Guam. The Guam Weather Forecast Office (WFO) issued a few Red Flag warnings indicating the danger for rapidly spreading grass fires.

The weather has been quieter in the region during the 1st Quarter of 2012 than it was last year at this same time when lightning was observed on several occasions in offshore convective cloud systems, and a tropical depression (02W) passed to the north of Guam and the CNMI in early April. Elevated sea levels were noted to have caused some minor coastal erosion along Guam’s southwestern coastline, where the spring tides of the most recent full moon cycle brought the sea high enough to allow wave action to scour sand and clay away from the root systems of coconut trees and other vegetation at the inland limit of the beach.

Guam and CNMI Rainfall Summary 1st Quarter 2012

Station   Jan. Feb. Mar. 1st Qtr
Predicted
Guam
Guam Intl. Airport (WFO)
Rainfall (inches)
6.50
2.85
4.45
13.80
12.29
% of Normal
146%
76%
149%
124%
11%
Anderson AFB
Rainfall (inches)
6.79
1.39
3.34
11.52
16.51
% of Normal
118%
27%
82%
77%
110%
University of Guam
Rainfall (inches)
6.86
3.39
4.29
14.54
12.29
% of WFO
154%
91%
144%
130%
110%
Ugum Watershed
Rainfall (inches)
8.24
3.36
4.71
16.31
16.51
% of AAFB
145%
64%
115%
109%
110%
Ypapao (Dededo)
Rainfall (inches)
7.27
4.36
5.38
17.01
16.51
% of AAFB
128%
84%
132%
113%
110%
Sinajaña
Rainfall (inches)
5.51
3.02
3.86
12.39
12.29
% of WFO
124%
81%
130%
111%
110%
Commonwealth of the Northern Mariana Islands
Saipan Intl. Airport
Rainfall (inches)
1.39
6.19
0.88
8.46
9.10
% of Normal
42%
248%
42%
107%
115%
Capitol Hill
Rainfall (inches)
2.05
3.77
1.30
7.12
10.64
% of Normal
51%
126%
52%
75%
115%
Tinian Airport
Rainfall (inches)
4.63
4.26
2.60
11.49
10.93
% of Normal
116%
142%
104%
121%
115%
Rota Airport
Rainfall (inches)
3.93
3.61
1.49
9.03
15.69
% of Normal
74%
77%
40%
66%
115%
Predictions made for 1st Quarter 2012 made in 4th Quarter 2011 Pacifc ENSO Update newsletter.

Climate Outlook: As was the case at this time last year, the status of ENSO is once again trending from La Niña to ENSO-neutral. This usually brings wetter weather to Guam and the CNMI. Unlike last year, however, there has not been an increase in heavy rain events nor other indicators of greater instability in the regional atmosphere during the 1st Quarter of 2012. Last year, the PEAC Center used these indicators to forecast an active rainy season for Guam and the CNMI with the occurrence of a few moderate or strong episodes of the southwest monsoon and an increase in rainfall extremes (e.g., 4 inches or more during a 24-hr period), and an increase in TC activity in regional waters. The former two of these three items did materialize during the latter half of 2011, but the return to La Niña in the fall of 2011 suppressed typhoon activity. The very quiet beginning to 2012 would suggest another tranquil year for the region. This would be more certain if the status of ENSO remains neutral for most of the remainder of the year, or goes back to La Niña, as it did in the fall of 2011. If the Pacific climate system evolves to El Niño, the weather could be active in the summer and fall of 2012, with some moderate or strong episodes of the southwest monsoon and an increase in the rainfall extremes. Also, if El Niño becomes established during the latter half of 2012, there would likely be an increase in TC activity in regional waters. The highest risk of a typhoon in the region occurs during El Niño, when the risk of gales (or higher) in regional waters increases 25 to 35% compared to non-El Niño years. We are now at the timing of a “predictability barrier” for ENSO. Thus, we cannot at this time choose with high confidence a preferred scenario for the evolution of ENSO over the course of the remainder of 2012, except to say that ENSO-neutral conditions should prevail in May and June. Most computer models are more strongly predicting a transition to El Niño than a return to La Niña.

Predicted rainfall for Guam and the Mariana Islands from April 2012 through March 2013 is as follows:

Inclusive Period

% of Long-Term Average Rainfall /
Forecast Rainfall (inches)
Guam/Rota
Saipan/Tinian
April– June 2012
(2nd Half of Dry Season)
120%
(19.71 inches)
120%
(10.30 inches)
July– September 2012
(Heart of Next Rainy Season)
120%
120%
October – December 2012
(End of Next Rainy Season)
110%
110%
January– March 2013
(Onset of Next Dry Season)
110%
110%

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
c/o NOAA NWS - Weather Forecast Office Honolulu
2525 Correa Road, suite 250
Honolulu, HI 96822
(808) 956-2324

Web Master's email: peac@noaa.gov
Page Last Modified: June 11 2012 21:48:40 GMT

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