State of Hawaii

MONTH: March 2009

PREPARED: April 7, 2009

State: [Text data table for rain gages]

The weather pattern over and near the Hawaiian Islands involved trade winds on most of the days during March. Two notable breaks in the trades occurred from March 7 through 9 and from March 12 through 19, both of which produced the month’s most significant rain events. On March 7, a strong upper level trough induced a surface trough that helped trigger heavy rainfall across windward areas of the state. At Hilo Airport, over 18 inches of rain in 2-days broke daily rainfall records for March 7 and 8. Flooding resulted in the closure of some secondary roads in the Hilo area but otherwise did not produce significant damages or injuries. Hanalei River on the island of Kauai briefly overflowed during the night of March 8 and into the early morning hours of March 9. Over windward Oahu, 5 to 8 inches of rain on the night of March 9 prompted the issuance of a flash flood warning and forced the closure of the Kamehameha Highway offramp on the H-3 Freeway.

Following a brief return of trade wind conditions, a strong low pressure system developed northeast of the Hawaiian Islands on March 12 then transitioned into a kona low type of system and moved westward. The formation location of this kona low was somewhat unusual since it occurred east of its normal formation area north to northwest of the state. A weak cold front swept across the state on the 12th and cool air surged over the island chain from the northwest. The trailing portion of a short wave trough rotating around the main low pressure center produced heavy showers and thunderstorms over Oahu and Maui County on March 14. A flash flood warning was issued during the morning hours due to heavy rainfall in the Ewa and Kapolei areas of Oahu but there were no reports of significant damage.

Trades returned at moderate to fresh levels on March 20 and persisted through the remainder of the month. While no flooding problems occurred during this time frame, windward areas, especially on the Big Island, saw frequent shower activity with the Glenwood rain gage recording more than 1 inch of rain on 6 out of the last 12 days of the month.

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

Rainfall totals across Kauai showed mixed signals during the month of March with several near to above normal totals interspersed with locations showing below normal totals. For example, gage totals from Lihue to Port Allen mainly fell within the range of 40 to 70 percent of normal. However, the totals from Kalaheo and Omao in between registered above 100 percent of normal. The U.S. Geological Survey (USGS) gage on Mount Waialeale recorded the state’s highest monthly total of 45.90 inches (132 percent of normal) and Kauai’s highest daily total of 6.15 inches on March 21.

Most of the gage totals for Kauai remained in the below normal range for 2009 through the end of March. Mount Waialeale’s year-to-date total of 92.21 inches (86 percent of normal) led all totals statewide. Most of the remaining sites had totals in the range of 40 to 70 percent of normal, which was a general improvement since February.

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

Most of the gages across Oahu recorded near to above normal rain totals for the month of March. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage recorded the highest monthly total of 25.03 inches (128 percent of normal) and the highest daily total of 7.71 inches during the heavy rain event of March 9. The March 9 event also included intense rainfall at the Maunawili and St. Stephens gages with 15-minute totals of 0.72 and 0.93 inches, respectively. In contrast, gages in west Oahu mostly recorded below normal monthly totals. For example, all locations in the Makua, Makaha, and Waianae Valleys reported totals at 60 percent of normal or less.

Most of the gages on Oahu have recorded below normal rain totals for 2009 through the end of March. The Oahu Forest NWR gage led all totals island-wide at 53.76 inches (103 percent of normal) and ranked eighth in the state. The abundance of trade wind days, especially in February and March, has resulted in well below normal totals in most of west Oahu.

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

Most of the gages on Maui and Kahoolawe recorded near to above normal totals during the month of March while gages on Molokai and Lanai recorded below normal totals. The USGS gage on Puu Kukui logged Maui County’s highest monthly total of 33.66 inches (85 percent of normal) and was the highest rainfall total at this location since January 2008. Puu Kukui also posted the highest daily total of 3.82 inches which occurred on March 15 and 29. On Molokai and Lanai, all of the gage totals fell within the range of 30 to 60 percent of normal.

Most of the rain gages across Maui County have recorded below normal totals for 2009 through the end of March. The USGS’ West Wailuaiki gage had the highest total of 61.23 inches (115 percent of normal), followed closely by the Puu Kukui total of 61.21 inches (62 percent of normal). Lahainaluna had the lowest total of 3.22 inches (34 percent of normal) so far this year. The extreme rainfall variability found in many areas of the Hawaiian Islands can be illustrated in west Maui where the Puu Kukui and Lahainaluna gages are less than 5 miles apart.

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

Most of the gages from the Hamakua District southward to the Kau District recorded above normal totals during the month of March. Piihonua’s 37.45 inches (182 percent of normal) led all Big Island totals and ranked second highest statewide. This included 12 days where daily totals exceeded 1 inch. Piihonua also posted the highest daily total of 9.91 inches during the March 7 heavy rain event. The Waiakea Uka gage also posted a notable 9.07 inches on the same date. Significant rainfall did not reach the west side of the Big Island and most of the gages along the Kona and leeward Kohala slopes posted below normal totals in the range of 40 to 70 percent of normal.

Windward Big Island gages all recorded near to above normal totals for 2009 through the end of March. In the leeward areas, most of the gages had below normal totals in the range of 40 to 70 percent of normal. Piihonua’s 62.30 inches (121 percent of normal) continued to lead all Big Island totals and ranked second in the state. This high ranking is a bit unusual and should slip over the next several months.

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