Guam/CNMI:  Rainfall on Guam during the 2nd Quarter and 1st half of 2008 was drier than normal. Persistent trade winds accompanied especially dry conditions (50-75% of normal) during the 2nd Quarter months. The rainfall totals during the first half of 2008 were approximately 25- 30 inches at all recording locations, ranging from 21.66 inches at Andersen AFB to 29.67 inches at the head of the Ugum watershed in the southern mountains. The weather on Guam during the first half of 2008 continued to be tranquil, with no unusually heavy rains or strong winds.

The 2nd Quarter 2008 and 1st half of 2008 rainfall totals in the CNMI were generally near normal, with six-month totals near 25 inches, similar to Guam. The island of Rota had a particularly wet May, with 11.49 inches recorded at the Rota Airport. This contributed to the highest six month accumulation in the region of 35.74 inches (116% of normal). The weather was otherwise very tranquil throughout the CNMI during the first half of 2008, with no unusually heavy rains or strong winds.

Guam and CNMI Rainfall Summary 2nd Quarter and 1st Half 2008

Climate Outlook: The rainy season on Guam and in the CNMI is off to a slow start with persistent trade winds accompanying hot and dry weather. There has been one episode of the southwest monsoon in early July, but it was weak and trade winds returned after the monsoonal clouds shifted to the west. All computer models available to PEAC Center indicate that the rainfall will be near normal in Guam and in the CNMI for the next three months, with no unusually heavy rains or strong winds expected. Although the basin climate has shifted to ENSO-neutral, the atmosphere is still behaving in a manner typical of La Niña. The persistent trade winds and ocean sub-surface heating in the western North Pacific will keep sea levels above normal. Tropical cyclone activity is anticipated to remain below normal in Micronesia through September, then return to near-normal levels during October, November and December. From August through December 2008, Guam and the CNMI can expect to be threatened by 2 or 3 tropical cyclones that will produces gales and hazardous seas in the island waters. The odds of destructive winds (60 mph or higher) from a typhoon on Guam and for each island of the CNMI will be approximately 10 to 15% for the remainder of 2008, which is the normal level of risk for a non-El Niño year.

Forecast rainfall for Guam and the CNMI from July 2008 through June 2009 is as follows:

source: UOG-WERI