MONTHLY PRECIPITATION SUMMARY

State of Hawaii

MONTH: October 2005

PREPARED: November 3, 2005

As the first month of the Hawaiian wet season, October produced several heavy rain events and wetter than normal conditions for many areas of the island chain.

The first significant heavy rain event of the month was a continuation of heavy rains that began on September 30 resulting from the low level remnant of Hurricane Kenneth passing beneath a strong upper level low pressure system. Very intense rains fell over portions of the Koolau Range on Oahu during the night of October 1 causing flash flooding on Kaukonahua Stream and the overflow of Lake Wilson at Wahiawa Dam. Sufficient water came over the spillway to force the evacuation of Otake Camp in Waialua. The heavy rains shifted southeastward and focused on Nuuanu and Kalihi Valleys, producing 6 to 12 inches of flowing water on Pali Highway and a few reports of homes flooded by heavy runoff. Damage estimates from the flooding were not available. Notable Oahu rain totals included just over 7 inches at Mililani and Waiawa and 10.25 inches at Nuuanu. At one point the Nuuanu gage recorded 1.6 inches in 15 minutes and 4.11 inches in one hour. Thunderstorms over eastern and central Kauai also produced very heavy rains during the night of October 1 with a peak 6-hour total of 6.17 inches recorded at Mount Waialeale. Flash flooding occurred on Hanalei River which forced the closure of Kuhio Highway at the Hanalei Bridge. Rapid water level rises also occurred on the Wailua River and the Hanapepe River, though no significant damages were reported along these waterways.

Mainly moderate to fresh trade winds dominated the Hawaiian Islands weather pattern from October 2 through October 18. Rain showers embedded within the trades brought daily rainfall to the east-facing slopes of the state though most daily totals remained below an inch during this period. On October 19, low level winds over the state veered to the southeast in response to a storm system northwest of the island chain. Brief heavy rains along the slopes of the Koolaus produced minor flooding though no reports of any significant damage.

On October 22 and 23, a shear line, the first of the 2005-2006 wet season, brought wet trades to many areas of the state. This event was followed on October 24 by a trade wind disturbance, sometimes referred to as a “screaming eagle” in reference to its appearance on satellite images. An upper level trough to the west of Kauai helped enhance the disturbance, producing thunderstorms and 2 to 4 inches of rain over windward and central Oahu. Flash flooding in the Kailua area forced the closure of the Kapaa Quarry Road.

Finally, during the early morning hours of October 31, terrain-induced heavy rains in southeasterly low level winds produced nearly 11 inches of rain in the Punaluu area of windward Oahu and 1 to 6 inches of rain along other areas of the Koolaus. Flash flooding inundated a home in Punaluu and produced significant runoff across Kamehameha Highway in the Kahana Valley area.

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

Most areas on the island of Kauai received above normal rainfall during the month of October. Mount Waialeale’s 49.77 inches marked the highest monthly total in the state and was a high total even by Waialeale standards at 164 percent of normal. The Mount Waialeale gage also recorded Kauai’s highest daily total of 10.81 inches during the flash flood event of October 1. In contrast, southwest Kauai and the Lihue area received below normal rainfall including less than 50 percent of normal totals at Lihue Airport, Port Allen, Hanapepe, and Makaha Ridge.

Rain totals for 2005 through the end of October were in the near to above normal range at most gages on the island of Kauai. Mount Waialeale leads all totals statewide with 316.55 inches (92 percent of normal). The highest percentage belonged to the USGS Hanalei River gage at 128 percent of normal.

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

For the second consecutive month, most gages on the island of Oahu recorded above normal rainfall during October. Drier than normal areas included west Oahu and the Hawaii Kai and Waimanalo areas of east Oahu. The Nuuanu gage’s 22.31 inches (223 percent of normal) led all of Oahu’s monthly totals followed closely by Manoa Lyon’s 22.17 inches (191 percent of normal). The highest 24-hour total came from the Punaluu Pump gage which recorded 10.70 inches between 11 AM on October 30 and 11 AM on October 31. Also impressive was the 7.30 inches recorded in 3 hours by the Nuuanu gage during the above mentioned flash flood event of October 1.

Rain totals for 2005 through the end of October remained at near to above normal levels at most of the gages across Oahu. The Manoa Lyon gage had the highest total for the year with 133.70 inches (106 percent of normal).

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

On the island of Maui, gages along the northeastern half of Haleakala and the West Maui Mountains recorded above normal rain totals during October, while leeward gages saw below normal rainfall. This contrast produced a wide range of monthly rain totals, from a low value of 0.02 inches at Kihei (3 percent of normal) to a high value of 37.70 inches at Puu Kukui (140 percent of normal). The Puu Kukui gage also posted the highest 24-hour total in Maui County with 13.06 inches between 6 PM on October 22 and 6 PM on October 23 during the passage of the wet season’s first shear line.

On the remaining islands in Maui County, most gages recorded below normal totals with 6 out of 8 posting less than 50 percent of October’s normal rainfall.

Rain totals for 2005 through the end of October remained at near to above normal levels at most sites throughout Maui County. Puu Kukui’s 302.05 inches (95 percent of normal) remains as the highest Maui County total and second only to Mount Waialeale’s 316.55 inches in the State of Hawaii. The lowest percentages come from Lahainaluna (69 percent of normal) and Honokanaia (77 percent of normal) on the southwest corner of Kahoolawe.

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

Gages on the windward side of the Big Island recorded above normal rainfall while most of the gages along the leeward side of the island posted below normal totals. The Glenwood gage logged the highest monthly total of 23.07 inches (226 percent of normal). However, it was the Pahoa gage that recorded the highest daily total of 4.01 inches on October 28 within a wet trade wind pattern. Both the Pahoa and Mountain View gages recorded measurable rain every day in October while Glenwood saw rain on 30 out of 31 days.

Rain totals for 2005 through the end of October remained at near to above normal levels at most gages on the Big Island. Mountain View’s 149.03 inches leads all Big Island totals. Several locations in the Hilo, Hamakua, and Kohala areas remain below normal for 2005 as a result of rain deficits earlier in the year. The Kau District also remains drier than normal.

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