State of Hawaii
Seasonal Precipitation Summary

Drought conditions continue to affect the entire state of Hawaii (see Figures 1a, 1b), as every county now has at least one location with some level of voluntary or mandatory water use conservation measure in place. In July, trade wind showers finally returned to expected summer levels, helping to stabilize drought conditions along the windward slopes of the Hawaiian Islands. The remnant of former tropical cyclone Elida brought frequent showers to the Big Island and Maui on July 22 and 23. Despite the return of trade wind showers, water use conservation notices and restrictions remained in place across the state.

Tropical activity affected the island chain throughout the month of August, including the remnants of former Hurricanes Genevieve (August 3 - 4) and Hernan (August 16). Of the two hurricane remnants, Genevieve’s impact was more significant, bringing a brief boost to windward rainfall\ with peak 24-hour totals of 1 to 4 inches at several locations. Hernan’s remnant moisture mainly affected the Big Island and did not provide much enhanced rainfall. On August 26, the City and County of Honolulu’s Board of Water Supply requested windward Oahu residents to cut back on water use by 10% on a voluntary basis.

Unlike the month of August, organized tropical weather systems did not play a significant role in shaping September rainfall across the island chain. An upper level low pressure system near Kauai helped support brief heavy afternoon showers over portions of Kauai and Oahu from September 11 - 14. A second, more persistent upper level low settled in near Kauai from September 21 - 25, triggering heavy showers over the Kona slopes during the late afternoon of September 21. On September 30, a weak cold front swept across the state and brought 0.25 to 0.50 inches of rain to several areas, and as much as 1 to 2 inches over some of the upper slopes. This frontal passage was noteworthy because it came unusually early; the first frontal passage of Hawaii’s wet season normally occurs during the latter half of October.

Water use conservation notices and restrictions continue to remain in place through early October, including a mandatory 30% reduction in irrigation water use for the Waimanalo Reservoir system and a mandatory 20% reduction for the Kualapu'u Reservoir system in west Molokai. Residents of central and Upcountry Maui remain under a request for voluntary reductions in water use by 10% and 5%, respectively. Effects of the drought so far have been greatest on the agriculture sector, especially in the cattle industry where some ranchers have reported stocking rates reduced by at least 50%, very poor pasture conditions, and even livestock deaths. The ongoing drought prompted the U.S. Department of Agriculture to declare the State of Hawaii a primary disaster area on August 1 for agriculture interests.

Additional individual rainfall station information and specific island information for Hawaii can be found in the Monthly Precipitation Summaries.

Hawaii Rainfall Summary for Select Stations, 3rd Quarter 2008

Climate Outlook: The following is in excerpt from the Climate Prediction Center’s official Seasonal Outlook Discussion for Hawaii ...

“NCEP models predict a tendency for below normal temperature for Hilo from November-December-January to December-January-February 2008-09. A tendency for above normal temperature us expected for Hilo from February- March-April to April May June 2009… for Kahului and Honolulu from January-February-March to April- May-June 2009… and for Lihue from December-January- February to April-May-June 2009. Models also predict below normal precipitation for all Hawaii stations from January-February March to March-April-May 2009.”