Guam and CNMI Vol.13, No.2

Guam/CNMI: The weather on Guam during the first quarter of 2007 was dry. The total rainfall for the first three months of 2007 was approximately 10 inches at all recording locations (ranging from 7.46 at the University in Mangilao to 11.47 inches at Ypapao in the north). These amounts, and those elsewhere on the island, were roughly 70% of the normal rainfall expected during this typically dry time of year. Wildfires have been frequent in March and early April, burning many hundreds of acres of grassland, particularly in the south. Several episodes of very large surf occurred on Guam in the first quarter, which is caused by intense extratropical low-pressure systems that move out into the North Pacific from East Asia and track towards the Gulf of Alaska this time of year. Most such storm systems race east and push high surf in the direction of Hawaii, but occasionally the winds line-up just right to send very high surf southward toward Guam or other islands of Micronesia.

The 1 st quarter rainfall totals in the CNMI were approximately the same as those experienced on Guam . At some locations in the CNMI the rainfall was actually slightly higher than at any Guam location. The highest amount of rain recorded in the CNMI for the 1 st quarter was 14.32 inches at the Rota Airport . Heavy rainfall during January 2007 was responsible for roughly half of the three-month total. Though the amounts of rainfall in the CNMI were quite dry when compared with other locations across the USAPI (see Fig. 1a), they were above normal at some locations (see Fig. 1b) because it is normally so very dry at this time of year. At the very beginning of April, Typhoon Kong-Rey passed just to the north of Saipan providing a shot of very welcome heavy rainfall for that island. Amounts of rain on Saipan associated with Kong-Rey totaled approximately 3 inches. Further south on Guam , the rainfall associated with the passage of Kong Rey was only one-half inch, which did little to alleviate dry conditions there. Rota received about 0.75 inches of rain, while Tinian had slightly less rain than Saipan .

Climate Outlook: Slightly below normal to near normal rainfall is anticipated throughout all of Guam and the CNMI during May and June 2007. Island residents are urged to continue their participation in voluntary water conservation measures. The rainy season should begin on time during July, with amounts near normal or slightly below normal for the remainder of the year. Tropical cyclone activity is expected to be below normal through August, returning to near normal from September through the remainder of the year. In an average year, Guam and the CNMI may expect to be threatened by 3 or 4 typhoons, with winds of typhoon force or greater expected to recur on average once every 5 to 7 years. Thus the odds of damaging winds from a typhoon on Guam and for all the islands of the CNMI are approximately 15 to 20% during any given year. Hazardous surf from a nearby or remote typhoon is experienced at least once each year.

Predicted rainfall for Guam and the CNMI from May 2007 through April 2008 is as follows:

Pacific ENSO Update

2nd Quarter, 2007 Vol. 13 No. 2