State of Hawaii


MONTH: August 2005

PREPARED: September 7, 2005

State: [Text data table for rain gages]

Rainfall during August across several areas of the state dropped off considerably from July’s totals. The largest decreases occurred on Kauai and Oahu where most gages recorded totals well below the August normals. A couple of heavy rain events, described below, helped save the island chain from more widespread rainfall deficits.

A surface low pressure trough associated with the remnant of Tropical Depression One-C helped bring heavy rains to the Big Island from August 6 through August 10. Minor flooding occurred along the Hilo and Hamakua districts on August 7, followed by thunderstorms and heavy afternoon rains over leeward Kohala on August 8. The heavy rains nearly caused a drainage ditch to overflow near the Belt Highway upslope from Waikoloa Village but otherwise did not cause any significant damages. A third and final round of heavy afternoon rains occurred on August 9 and produced flash flooding in the Kau and Kona areas of the Big Island. Runoff in Hilea Gulch forced the brief closure of the Belt Highway at Kawa Flats between Pahala and Naalehu. The town of Kealakekua in Kona also experienced minor damage to several properties.

The second bout of heavy rains took place on August 28 through August 30 as a low pressure system moved westward to the north of the island chain. The unstable airmass supported heavy afternoon showers over Kona on August 28 and over the Waianae and Makaha areas of Oahu on August 29. The west Oahu rains helped trigger a small landslide that affected Farrington Highway.

The remnant of Hurricane Fernanda brushed the Big Island and Maui on August 19 but did not produce any significant flooding.

Island of Kauai: [August 2005 map] [Year-to-date map]

August rain totals on Kauai marked a significant drop off from July’s near to above normal amounts with all gages recording less than 50 percent of normal rainfall. Mount Waialeale’s total of 13.67 inches was the second lowest August total on record, surpassed only by the 13.47 inches in August 1971. Lihue Airport’s 0.64 inches also marked the second driest August on record while gages at Wainiha, Wailua, and Hanalei posted the lowest August totals since records were established in 1991.

Rain totals for 2005 through the end of August have slipped to below normal levels at several sites on the island of Kauai. Amounts ranged from 66 percent of normal at Lihue Variety Station to 100 percent of normal at Makaha Ridge.

Island of Oahu: [August 2005 map] [Year-to-date map]

Most locations on the island of Oahu experienced dry conditions during the month of August with over half of the gages recording less than 50 percent of normal rainfall. The notable exception was the Makua Ridge gage which posted 417 percent of normal rainfall. Most of this total occurred on August 29 when 4.58 inches fell between noon and 6 PM HST causing minor flooding and a small landslide on Farrington Highway. The Manoa Lyon gage recorded the same monthly total as the Makua Ridge gage, but the 5.84 inches in a normally wet Manoa Valley marked the third driest August since the establishment of data records in 1975.

Dry conditions during August dropped several sites into below normal territory with 10 sites reporting less than 70 percent of normal rainfall for 2005. The Manoa Lyon gage continued to have the highest Oahu total for the year at 90.56 inches (88 percent of normal).

Maui County: [Maui August 2005 map] [Year-to-date map] [Molokai/Lanai August 2005 map][Year-to-date map]

Maui County recorded a wide range of rainfall conditions, from 17.53 inches at West Wailuaiki (89 percent of normal) to 0.04 inches at Kihei (20 percent of normal). The highest county-wide monthly total likely belongs to the Puu Kukui gage, but data from this remote site were not yet available at the time of this report. The West Wailuaiki gage also posted the highest daily total of 5.29 inches on August 19 as the remnant of Hurricane Fernanda moved westward past the island chain. Percent of normal values ranged from 800 percent at Kaunakakai and 194 percent at Kula to just 11 percent at Kamalo. For Kaunakakai, with an August normal of only 0.10 inches, a single rain event that dropped 0.79 inches during the midday hours of August 1 resulted in the very high percentage value.

Rain totals for 2005 through the end of August remained at near to above normal levels for most sites across Maui County. Although the August total for Puu Kukui is not yet available, it likely remains the wettest spot in the state so far this year due to the dry conditions over Mount Waialeale. The highest percent of normal value belongs to the Kaunakakai gage (16.38 inches, 158 percent of normal) while the lowest is from the Kaupo Gap site at 58 percent of normal (34.58 inches).

Island of Hawaii: [August 2005 map] [Year-to-date map]

Heavy rain events from August 7 through August 9 and on August 28 along the leeward sections of the Big Island produced near to above normal totals at gages in the Kona and South Kohala areas. Heavy rains also affected the east-facing slopes of the island on August 6 and 7 but overall dryness during the rest of the month meant below normal totals at several Hilo, Hamakua, and Puna gages. Although the Mountain View gage recorded the highest monthly total (12.56 inches) and highest daily total (5.26 inches on August 7), the most intense rains occurred at the Kealakekua gage on August 9. With heavy rains occurring over several locations in the Kona and Kau areas, the gage at Kealakekua registered 0.81 inches in 15-minutes and 2.24 inches in the 1-hour period from 4:15 PM to 5:15 PM HST.

Most of the gages across the Big Island had 2005 totals through the end of August at near to above normal levels. The North Hilo, South Hilo, and Kau Districts indicated the driest overall conditions for 2005 with totals between 50 and 80 percent of normal. Mountain View’s 100.07 inches continued to be the highest Big Island total so far this year.

Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lihue, Honolulu, Kahului, and Hilo, HI, the Hydronet state network of automated rain gages, and selected Cooperative Observer sites. Additional data come from automated rain gages operated by 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