State of Hawaii

MONTH: August 2009

PREPARED: September 9, 2009

State: [Text data table for rain gages]

August began with trade winds at mainly moderate to fresh levels across the Hawaiian Islands. The trades on August 1 and 2 may have been enhanced by Tropical Storm Lana as it moved westward to the south of the state. Daily showers embedded within the trade flow primarily affected the windward slopes of the islands.

The most significant weather event of the month occurred from August 11 through 14 as the remnant circulation of former Hurricane Felicia moved across the mid-section of the island chain. The abundant low level moisture helped produce much needed rainfall from Maui to Kauai. Heavy rainfall over windward Oahu on August 13 caused flash flooding in Waikane Stream and a temporary closure of Kamehameha Highway. Enhanced windward rainfall on Kauai caused water levels in Hanalei River to rise but not enough to force the closure of Kuhio Highway at the Hanalei Bridge. Unfortunately for drought-stricken leeward areas on the Big Island, most of the significant rainfall associated with Felicia’s remnant passed north of the island or remained confined to the windward slopes and isolated spots over the Kona slopes.

Island of Kauai : [August 2009 map] [Year-to-date map]

Most of the rain gages on Kauai recorded near to above normal rainfall for the month of August. Rainfall associated with the remnant of Hurricane Felicia provided a significant boost to the totals at most sites. The U.S. Geological Survey’s (USGS) gage on the summit of Mount Waialeale posted the state’s highest monthly total of 36.83 inches (94 percent of normal). This gage also reported Kauai’s highest daily total of 7.85 inches on August 13 during the passage of Hurricane Felicia’s remnant circulation. Both the Kapahi and Wailua gages recorded measurable rainfall (0.01 inches or greater) on 30 out of 31 days in August.

Island of Oahu: [August 2009 map] [Year-to-date map]

Above normal totals at most of the windward and west Oahu gages bracketed below normal totals recorded at central Oahu sites. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage recorded the highest monthly total of 20.91 inches (128 percent of normal). This gage also recorded the highest daily total of 8.50 inches on August 12 during the flash flood event associated with the remnant of Hurricane Felicia. The 1 to 2 inches recorded at several of the west Oahu gages may not seem like much, but considering the time of year and location these amounts are two to four times the normal for August.

Maui County: [Maui August 2009 map] [Year-to-date map] [Molokai/Lanai August 2009 map] [Year-to-date map]

Most of the gages across Maui County received near to well above normal rainfall during the month of August. The 2.91 inches at Kula and the 1.47 inches at Kihei registered as the highest August totals in the available data archives dating back to January 1991 and August 1992, respectively. The USGS gage at West Wailuaiki posted the highest available monthly total of 18.58 inches (94 percent of normal). The Puu Kukui gage may have received more rainfall but a mid-month equipment outage resulted in a partial loss of record.

Island of Hawaii: [August 2009 map] [Year-to-date map]

Despite the almost daily rainfall, all of the windward Big Island gages in the North Hilo, South Hilo, and Puna Districts recorded below normal rainfall for the month of August. A breakdown of the totals from Hilo Airport showed that daily amounts were about half of normal. None of the Puna or South Hilo gages recorded any daily totals of an inch or more which is somewhat unusual within an August trade wind pattern. The highest daily total came from the Kealakekua gage in the South Kona District which measured 2.77 inches on August 11.

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