State of Hawaii

MONTH: May 2007

PREPARED: June 5, 2007

State: [Text data table for rain gages]

The month of May continued the overall dry conditions seen in April with trade winds interrupted several times by an unseasonal shift of the subtropical ridge of high pressure toward the Hawaiian Islands. These shifts resulted in weaker than normal or a complete cessation of trades and an increase in stability of the local airmass. Weak middle and upper level troughing on May 13 introduced some instability that supported brief moderate to heavy afternoon showers over the central and western sections of Oahu.

The trade winds, when they did manage to blow, were mainly in the moderate range with a period of moderate to fresh conditions from May 8 through May 11.

Ongoing dryness coupled with the seasonal increase in temperatures has produced some drought type impacts on several islands, primarily in the agriculture sector. These include a call for voluntary irrigation water conservation in the Waimanalo area and a voluntary reduction notice for portions of the Kau District on the Big Island . Livestock farmers have also reported impacts due to degraded pasture conditions, especially in the leeward areas of Maui and the Big Island.

Island of Kauai : [May 2007 map] [Year-to-date map]

All of the gages on Kauai recorded below normal totals for May with most totals at less than 30 percent of normal. Problems with the Mount Waialeale gage resulted in a missing total but available data suggested a monthly total near 20 inches in the range of 50 to 75 percent of normal. Next to Mount Waialeale , the second highest total came from Anahola at 2.44 inches (76 percent of normal). Anahola also had the highest daily total of 1.46 inches on May 14.

All Kauai rain totals for 2007 through the end of May were in the below normal range. Wailua’s 26.06 inches marks the highest percent of normal value at 73 percent.

Island of Oahu: [May 2007 map] [Year-to-date map]

Most of the Oahu gages recorded below normal rain totals for the month of May. The exceptions came from central Oahu and the Waianae/Makua area where brief moderate to heavy showers during the afternoon of June 13 produced 1 to 2 inch 24-hour totals that pushed monthly totals above 100 percent of normal. May’s highest total was 11.19 inches from the Oahu National Wildlife Refuge (NWR) gage which translated to 64 percent of normal. This site also had the highest daily total of 2.16 inches on May 18. Honolulu Airport’s 0.12 inches (15 percent of normal) marked the fourth driest May in the past 30 years. The driest May on record at this location was in 2000 which saw only 0.03 inches.

All Oahu rain totals for 2007 through the end of May fell within the near to below normal range. The Oahu Forest NWR total of 66.98 inches (74 percent of normal) leads all island-wide totals and has moved up to 3rd highest in the state behind only Mount Waialeale on Kauai and Puu Kukui on Maui.

Maui County: [Maui May 2007 map] [Year-to-date map] [Molokai/Lanai May 2007 map] [Year-to-date map]

All of the gages in Maui County recorded near to below normal totals during May with most at less than 50 percent of normal. West Wailuaiki recorded the highest monthly total of 6.92 inches though this was only 39 percent of the May normal. Puu Kukui, normally the second wettest spot in the state, posted a monthly total of only 5.76 inches (16 percent of normal) but did have the highest daily total of 1.21 inches on May 12. Three sites, Lahainaluna, Kihei, and Pukalani, posted monthly totals of 0.00 inches while Waikapu Country Club recorded only 0.02 inches.

Rain totals for 2007 through the end of May are at near to below normal levels at all locations across Maui County. Puu Kukui’s 69.60 inches (40 percent of normal) continues to rank 2nd in the state while West Wailuaiki ranks as 4th highest.

Island of Hawaii: [May 2007 map] [Year-to-date map]

All Big Island gages recorded below normal totals for the month of May with more than half of the sites at less than 30 percent of normal. In fact, no gages reported a monthly total above 5 inches. The last time this happened was in June 2004 when all gage totals were less than 3 inches. Glenwood posted the highest monthly total (4.10 inches, 34 percent of normal) but it was the Kealakekua gage that had the highest daily total with 1.02 inches on May 21.

Rain totals for 2007 through the end of May remained in the near to below normal range for all Big Island gages. Glenwood’s 63.65 inches (77 percent of normal) is the highest total on the island and has slipped to 5th highest in the state.

Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lïhu‘e, 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