State of Hawaii

MONTH: February 2008

PREPARED: March 5, 2008

State: [Text data table for rain gages]

February 2008 started with immediate impacts from heavy rains as an upper level trough destabilized the underlying moist trade winds, producing significant flooding in the Hilo area of the Big Island and over the north- and south-facing slopes of Kauai. For the east Big Island residents, it was the most significant flood event since the intense November 1-2, 2000 severe flood event. Initial assessments by Hawaii County officials indicated 100 to 150 homes received damages, primarily in the Waiakea area of Hilo due to the overflow of Waiakea Stream and nearby drainage ditches. Fortunately, officials reported no significant injuries or deaths due to the storm. The February 2008 event will be known more for its duration than its intensity with 20 to 40 inches spread out over a 5-day period. Back in November 2000, a similar amount of rain was compressed within a 36-hour period, including a phenomenal 22 inches in 6-hours at Kapapala Ranch in Kau.

Heavy rains over Kauai occurred mainly on February 3, initially along north-facing slopes in the morning hours which forced the closure of both the Wainiha and Hanalei Bridges along Kuhio Highway. In the afternoon, the heavy rains shifted to the south-facing slopes with nearly 8 inches recorded in 6-hours (1 PM HST to 7 PM HST) at the Mount Waialeale gage. Radar-based rainfall estimates showed similar amounts over the higher elevations of the south-facing slopes above Hanapepe and Waimea. The USGS gage on Makaweli River indicated a new record water level (unofficial) of 15.56 ft., just beating the previous record of 15.51 ft set on January 31, 1975. High water levels in Hanapepe River forced the evacuation of some residents in Hanapepe Valley and came close to overflowing a levee protecting Hanapepe town.

On February 6, Oahu received its turn when thunderstorms generated heavy rains over the central Koolau Range during the evening hours. Emergency managers closely monitored the situation at Lake Wilson in case water levels became high enough to force the evacuation of residents in Otake Camp near Waialua. In the end, the thunderstorms dissipated and no evacuations were needed.

A surface trough over the mid-section of the state helped trigger yet another round of heavy rains on February 7. Afternoon thunderstorms over central and southwest Oahu produced rain rates of 2 to 4 inches per hour over the Makakilo, Kapolei, and Ewa areas. Substantial runoff resulted in 3 to 4 feet of water in the west-bound lanes of the H-1 Freeway near Makakilo during the peak afternoon traffic hours. Activity subsequently shifted to east Molokai where heavy rains and flooding briefly forced the closure of the Kamehameha V Highway near Mile Post 10.

The final round of heavy rains occurred over the South Kona slopes of the Big Island on the afternoon of February 8. A flash flood warning was issued when the rain gage at Honaunau reported 0.82 inches in a 15-minute period (4:00 PM to 4:15 PM HST) but fortunately produced only minor flooding problems.

A more stable trade wind pattern returned on February 9, followed by a southward shift of the low level high pressure ridge to a location near the Hawaiian Islands. The resulting stable, light wind pattern persisted through most of the remainder of the month, broken briefly by the passage of a weak cold front on February 24 and 25. Rain totals associated with the frontal passage were mostly less than an inch with a few spots in the 1 to 2 inch range.

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

Rain gages on Kauai showed a wide range of totals with just over half of the sites showing below normal totals for the month of February and the remaining sites indicating near to well above normal totals. The U.S. Geological Survey’s (USGS) gage on Mount Waialeale recorded 42.86 inches (124 percent of normal), the highest total on the island and the second highest in the state. In contrast, Lihue Airport recorded only 1.34 inches (41 percent of normal). The Mount Waialeale gage also recorded the highest daily total of 12.73 inches during the flash flood producing rains on February 3. Radar rainfall estimates indicated higher totals over the south-facing slopes of the island between the Mount Waialeale gage and the towns of Hanapepe and Waimea.

Rain totals at most sites for 2008 through the end of February were in the below normal range. The Mount Waialeale total of 66.22 inches (91 percent of normal) leads all values statewide. Lihue Airport has recorded only 2.53 inches (32 percent of normal) so far this year, the lowest January-February total since 1993.

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

Most locations on Oahu posted below normal rain totals, especially those sites in the east side of the island such as Waimanalo and the Hawaii Kai Golf Course which recorded totals less than 20 percent of normal. Several gages situated within the interior sections of the Koolau Range recorded near to above normal totals including the U.S Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage which had the highest Oahu total of 15.32 inches (94 percent of normal). The Nuuanu gage recorded the highest daily total of 3.69 inches on February 6 while the Manoa Lyon Arboretum gage recorded 7 consecutive days with more than an inch of rain from February 2 through 8.

Rain totals for 2008 through the end of February were in the below normal range for most sites on Oahu. The exceptions which had near to above normal totals mainly came from interior Koolau sites such as Manoa Lyon (27.87 inches, 131 percent of normal) and South Fork Kaukonahua (18.40 inches, 122 percent of normal).

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

Gages across Maui County turned in the usual wide range of values, from 23.68 inches at Puu Kukui (82 percent of normal) to 0.58 inches at Waikapu Country Club (17 percent of normal) only 6 miles away. Monthly totals from the Puu Kukui gage normally register in the state’s top 3 totals each month but the heavy rains over the windward side of the Big Island pushed Puu Kukui down to 10th place. West Wailuaiki had the highest daily total of 6.22 inches on February 2. All sites on Molokai and Lanai posted totals at less than 40 percent of normal.

Most of the gages across Maui County had below normal totals for 2008 through the end of February. Puu Kukui’s 57.59 inches (98 percent of normal) led all gages county-wide and ranked 2nd in the state. All totals from Molokai and Lanai were below 30 percent of normal so far for 2008.

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

Most of the gages on the Big Island recorded well above normal rain totals for the month of February. Several gages showed 20 to 40 inch totals through the first 5 days of the month, led by 40.81 inches at the Waiakea Experiment Station (not yet depicted on the maps), 37.30 inches at Waiakea Uka, and 29.72 inches at Hilo Airport. The Hilo Airport total through February 5 ranked as the 4th wettest February on record. However, the lack of rain during the rest of the month did not allow the February 2008 total to break the all time February record of 45.55 inches set in 1979. Also on February 5, Hilo Airport set a new record for the wettest 7-day period (January 30 through February 5) with 35.32 inches beating the old record of 34.00 inches set on March 13 through 19, 1980. The highest daily total for the month came from the Waiakea Experiment Station with 17.83 inches followed by Waiakea Uka’s 16.34 inches, both on February 2.

Not all Big Island gages indicated wet conditions. In North Kona, the Puu Waawaa gage recorded only 0.61 inches (23 percent of normal) for the month.

Rain totals for 2008 through the end of February were above normal for most of the gages across the Big Island. The Waiakea Uka total of 57.57 inches (199 percent of normal) topped all totals island wide and ranked 3rd in the state. Totals from gages in the Kohala and Pohakuloa areas were in the below normal range.

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