MONTHLY PRECIPITATION SUMMARY

State of Hawaii

MONTH: December 2005

PREPARED: January 6, 2006

While the first week of December provided some active weather over the Hawaiian Islands, the airmass became quite stable for the remainder of the month to produce very dry conditions for most areas of the state.

The month’s most active weather event occurred on December 4 as low level convergence ahead of a poorly defined cold front pushed across Kauai and Oahu. Thunderstorms developed over the eastern half of Oahu during the afternoon hours and produced brief but intense showers which overwhelmed a storm drain and sent flood waters into a home near Kaneohe. The storm system also generated a small tornado that damaged roofs and uprooted several large trees in Aiea. Fortunately, no serious injuries were reported though lightning strikes did produce brief power outages to more than 3000 Oahu residents. Remnant low level moisture supported by unstable conditions aloft helped trigger heavy showers and minor flooding the following afternoon over the Kona slopes of the Big Island.

On December 7 and 8, an upper level trough over low level moderate trade winds brought unstable conditions to the windward sections of the Big Island. Moderate to heavy showers produced minor flooding in the Hilo, Puna, and windward Kohala areas but no significant damages or injuries.

Following a period of moderate trades from December 9 through December 14, the subtropical ridge of high pressure settled over the island chain, pushed southward by a series of strong storms in the northwest Pacific. The presence of the ridge over the state resulted in very stable conditions, little or no rain, and winds dominated by local land and sea breezes. This stable weather pattern persisted for the rest of the month, interrupted briefly by fast-moving but “dry” cold fronts on December 18 and 22 and by a weak shear line on New Year’s Eve. While not a significant rain maker, the December 18 cold front brought strong southwest winds that produced damage over northeast Oahu and contributed to the death of a toddler in Maunawili.

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

The island of Kauai experienced record-setting dryness during the month of December with all gages reporting below normal totals and most at less than 10 percent of normal. All time records for the driest December were broken at Lihue Airport (0.08 inches, previous record 0.51 inches in 1985) and Mount Waialeale (1.67 inches, previous record 3.18 inches in 1983). For Mount Waialeale, known as one of the world’s wettest spots, the December total of 1.67 inches was only 4 percent of its normal of over 45 inches and amazingly not among the top 20 monthly totals statewide.

Rain totals for 2005 ended up in the near to below normal range for most of the gages on Kauai with most amounts between 50 and 80 percent of normal. Although the fall months have been dry, Mount Waialeale closed out the year with the state’s highest total of 343.82 inches (81 percent of normal), ahead of Puu Kukui on Maui by just over 5 inches. The lowest total came from the Port Allen gage which recorded only 16.03 inches all year.

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

All gages on Oahu recorded well below normal totals for the month of December and more than half of the sites posted totals at less than 10 percent of normal. Several sites, especially over the western half of the island posted record-breaking totals for the driest December. These sites include Waiawa Correctional Facility (data since 1992), Palisades (data since 1991), and Kahuku (nearly continuous data since 1905!). Waianae’s 0.01 inches marked the driest December since 1952. For the eastern half of the island, most locations recorded more than half of their rain during the December 4 heavy rain event, including Kaneohe Marine Base which observed 1.20 inches between 2:00 and 3:00 PM.

Rain totals for 2005 ended up at near to below normal levels at most locations on Oahu following the dry conditions of December. Manoa Lyon ended up with the highest island-wide total of 151.46 inches (100 percent of normal). Waianae Boat Harbor posted the lowest total of only 14.12 inches for the year.

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

All gages across Maui County recorded below normal rain totals during December. Puu Kukui led all gage totals county-wide with 6.66 inches but far below the December normal of over 36 inches. Although Lahainaluna’s 0.01 inches set a new record for the driest December (data since 1991), other sites managed to avoid record-setting totals.

Rain totals for 2005 ended up at near to above normal levels at most location in Maui County despite the rather dry conditions during December. Puu Kukui finished the year with the second highest statewide total of 338.75 inches, falling short of Mount Waialeale by just over 5 inches.

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

Early December rains across the windward side of the Big Island produced some of the highest monthly totals statewide, but totals were still well below normal. Most gages reported less than 50 percent of normal rainfall with Kau, North Kona, and Pohakuloa area gages coming in at below 25 percent of normal. Wet trade wind weather on December 7 and 8 dropped 3 to nearly 5 inches of rain over portions of Hilo, Puna, and Hamakua but subsequent stable conditions produced mostly zeroes for daily totals afterward.

Rain totals for 2005 ended up at near to below normal levels at most of the Big Island gages. Mountain View finished the year leading all Big Island totals with 168.88 inches (99 percent of normal). Keahole Airport finished with the highest percent of normal value of 168 percent, mainly due to rainfall during the first half of the 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