State of Hawaii

MONTH: August 2008

PREPARED: September 5, 2008

State: [Text data table for rain gages]

Trade winds dominated the Hawaiian Islands’ weather pattern throughout the month of August with speeds mainly in the moderate to fresh range for the first 3 weeks then becoming light to moderate during the last week. Although the persistent trades have been producing the normal high frequency of measurable daily rain along windward slopes, the amount of rain falling per day is lower than normal. For example, Hilo Airport has an average of 26 days in August with measurable rain (0.01 inches or greater) and 5 days with 0.50 inches or more rain. In August 2008, the Hilo Airport gage recorded measurable rain on 25 days (near normal) but there were no days with totals at or above 0.50 inches. Similar results have been observed at other locations in the state exposed to trade wind shower activity.

Tropical weather activity affecting the island chain included the remnant clouds and showers of former hurricanes Genevieve (August 3 and 4) and Hernan (August 16). Tropical Storm Kika, which initially developed as Tropical Depression 1-C far south-southeast of the Big Island, did not affect statewide weather conditions. Of the two hurricane remnants to affect the islands, Genevieve’s remnant 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 of an enhancement to rainfall.

Drier than normal conditions continued over many areas of the state resulting in the persistence or worsening of drought conditions, especially for the agriculture industry. 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 percent on a voluntary basis. Elsewhere across the state, existing water use conservation notices and restrictions remained in place. This included a mandatory 30 percent reduction in irrigation water use for the Waimanalo Reservoir system and a mandatory 20 percent reduction for the Kualapuu Reservoir system in west Molokai. Residents of central and Upcountry Maui remained under a request for voluntary reductions in water use by 10 and 5 percent, respectively. The ranching industry has been hit especially hard by the drought due to severely degraded pasture conditions and other impacts to operations. 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.

Island of Kauai : [August 2008 map] [Year-to-date map]

Just over half of the available gages on Kauai recorded near to above normal rainfall during August. The remaining gages were in the range of 50 to 80 percent of normal. The U.S. Geological Survey (USGS) gage on Mount Waialeale recorded the highest monthly total statewide (28.46 inches, 73 percent of normal) and the highest daily total of 3.54 inches on August 3 during the passage of ex-Hurricane Genevieve’s remnant moisture across the island.

Rain totals for 2008 through the end of August remained at below normal levels at most locations on Kauai. The Mount Waialeale gage total of 216.52 inches (76 percent of normal) remained well above all other totals statewide. Most of the remaining Kauai gage totals were in the range of 40 to 70 percent of normal for the year-to-date.

Island of Oahu: [August 2008 map] [Year-to-date map]

Most of the gages on the island of Oahu posted near to below normal totals for the month of August. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage near the crest line of the Koolau Range recorded the highest monthly total on the island with 10.41 inches (64 percent of normal). The highest daily total of 1.50 inches came from the USGS’ Poamoho 2 gage on August 3 in association with ex-Hurricane Genevieve’s remnant shower area.

Rain totals for 2008 through the end of August remained below normal at most of the gages on Oahu. The only exception is the USGS gage at the South Fork Kaukonahua Stream site which remains in the near normal range at 92 percent for the year-to-date. Most of the remaining sites were in the 30 to 60 percent of normal range. The Oahu Forest NWR gage has the highest year-to-date total of 86.75 inches (63 percent of normal) and climbed up to sixth highest statewide.

Maui County: [Maui August 2008 map] [Year-to-date map] [Molokai/Lanai August 2008 map] [Year-to-date map]

As is often the case, Maui County rain data exhibited the widest range of conditions in the state. In south Maui alone, August percent of normal values ranged from 15 percent at Kihei to 296 percent at Ulupalakua just 7 miles away. Upcountry Maui rainfall has been interesting this summer with Ulupalakua sitting within a narrow wet belt along the southwest rift of Haleakala surrounded by drought stricken, desiccated pastureland. In July and August, the Ulupalakua gage recorded 10.10 inches of rain which translated to 374 percent of normal while the Kula gage 9 miles away recorded only 0.62 inches, or 39 percent of normal. During both months, the Ulupalakua area received an unusual number of heavy rain days for the summer with 5 instances of daily totals at or above 1 inch. On average, the Ulupalakua gage does not record any daily totals at this level during July and August.

The USGS gage on Puu Kukui recorded the highest Maui County total of 16.33 inches but this was only 50 percent of the normal August value. This gage also recorded the highest daily total of 2.51 inches on August 10.

Most of the Maui County rain totals for 2008 through the end of August remained in the below normal range. Puu Kukui’s 143.83 inches (54 percent of normal) led all county totals and ranked second in the state.

Island of Hawaii: [August 2008 map] [Year-to-date map]

All of the Big Island gages recorded below normal rainfall totals for August with most amounts in the range of 30 to 60 percent of normal. The Glenwood gage recorded the highest monthly total of 6.41 inches, though this was only 56 percent of normal and marked the lowest August total for this gage in the archive going back to 1993. The Honaunau gage posted the highest daily total of 1.16 inches on August 30. Hilo Airport’s 3.72 inches was the fourth lowest August total since the site became established in 1949.

Most of the Hilo and Puna gages had near normal rain totals for 2008 through the end of August as a result of excessive rainfall early in the year. Waiakea Uka’s 100.88 inches (82 percent of normal) continued to lead all Big Island totals and ranked fourth statewide.

Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lïhue, Honolulu, Kahului, and Hilo, the Hydronet state network of automated rain gages, and selected Cooperative Observer sites. Additional data come from automated rain gages operated by the State of Hawai‘i Department of Land and Natural Resources, the US Geological Survey, the US Bureau of Land Management, the US National Park Service, the Department of Defense, and the US Fish and Wildlife Service. Data presented here are not certified and should be used for information purposes only.

Kevin R. Kodama
Senior Service Hydrologist
NOAA/NWS Weather Forecast Office Honolulu