The 6-month average of the SOI during the latter half of 2006 was near - 0.9. A comparison of the average of the SOI during July through December with the rainfall on Guam during the first 6 months of the year to follow (Fig. 5) shows that the climate system (in terms of the SOI) is near an historical break-point where the rainfall is always well below normal (see bottom oval in Fig. 5). This is fairly representative of the effects across most of Micronesia, except for Majuro, Kosrae and Pohnpei, which can still have normal rainfall with an SOI value near –1.0.

Figure 5 . A comparison of the 6-month July-through-December average of the Southern Oscillation Index (SOI) with the rainfall on Guam during the January through June of the following year. Note that when the value of the average of the SOI is below –1.0 during the previous year’s July through December, the rainfall on Guam has always been very dry during January through June. The value of the SOI for July through December 2006 was -0.9, which is right at the threshold of historical occurrences of very dry conditions during January through June.