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NOAA > NWS > WFO HFO Home Page > Hydrology > August 2012 Precipitation Summary
August 2012 Precipitation Summary

State of Hawaii

MONTH: August 2012

PREPARED: September 6, 2012

Note:  This summary uses the arithmetic mean, or average, for “normal” rainfall values.

State: [Text data table for rain gages]

Trade winds persisted through the month of August at mainly moderate speeds.  The trades brought rainfall to the windward slopes on an almost daily basis though amounts on many days were below the long term average.

A couple of weather features moving across the area helped produce enhanced rainfall for brief periods during the month.  On August 20, a low- to mid-level trough helped boost shower activity across the windward slopes of the Big Island.  Daily totals fell into the 1- to 4-inch range and pushed streams to their highest levels for the month but did not cause any significant damage.  Lingering moisture from the trough helped enhance afternoon showers on August 22 over the leeward slopes of Haleakala on Maui near Ulupalakua.  Radar data and spotter reports showed 1 to 2 inches of much needed rainfall.  On August 29, a middle and upper level low northwest of Kauai increased the depth of the moist layer which helped increase showers along the windward and upper slopes of Kauai and Oahu.  The highest daily totals from Kauai fell into the range of 3 to 6 inches while Oahu totals hit 1 to 2 inches.

The persistent trade winds meant that leeward areas remained dry overall.  Extreme drought remained in place over some of the leeward areas of the Big Island and Maui County.  Drought intensified over south Kauai and leeward Lanai.  For more information on the ongoing drought, please refer to the latest Drought Information Statement at:

Island of Kauai : [August 2012 map] [Year-to-date map]

While there were a few sites with monthly totals near the August average, most sites on Kauai reported below average totals.  The U.S. Geological Survey’s (USGS) Mount Waialeale gage had the state’s highest monthly total of 29.24 inches (84 percent of average) and the highest daily total of 6.30 inches on August 29.  Lihue Airport’s 1.00 inches (47 percent of average) made it the driest August in the past five years and Hanapepe’s 0.21 inches (14 percent of average) was the lowest August total for this site in a period of record going back to 1993.

Rainfall totals for 2012 through the end of August were still in the near to above average range at most locations due to the wet conditions early in the year.  Mount Waialeale’s 261.87 inches (100 percent of average) led all year-to-date totals across the state.

Island of Oahu: [August 2012 map] [Year-to-date map]

Most of the gages on Oahu posted below average rainfall totals for the month of August with many amounts in the range of 30 to 60 percent of average.  The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage had the highest monthly total of 10.15 inches (53 percent of average) and the highest daily total of 1.67 inches on August 29.  The Manoa Lyon Arboretum gage recorded rainfall on 26 out of 31 days in the month which is just shy of the long term average of 27 days.  However, daily rainfall at this site was below average especially in the first half of the month.

Many of the gages on the slopes of the Koolau Range had totals in the near average range for 2012 through the end of August.  Year-to-date totals for the remaining Oahu gages were mainly in the below average range.  The Oahu Forest NWR gage had the highest total of 127.54 inches (89 percent of average) which was fourth highest statewide.

Maui County: [Maui August 2012 map] [Year-to-date map] [Molokai/Lanai August 2012 map] [Year-to-date map]

Most of the gages across Maui County recorded below average rainfall for the month of August. The USGS gage on Puu Kukui had the highest monthly total 21.93 inches (65 percent of average) and the highest daily total of 4.24 inches on August 20 and again on August 23.  These daily totals exceeded the monthly totals at all of the other gages on the island of Maui.  Molokai Airport’s 0.63 inches marked only the second time in two years that this location has had a near average monthly total.

Most of the Maui County gages had below average rainfall totals for 2012 through the end of August.  Puu Kukui had the highest year-to-date total of 192.33 inches (75 percent of average) which was the second highest in the state.  Ulupalakua Ranch is on pace to have its driest year ever.  Its 2012 total through August is 8.10 inches and the record low annual rainfall total is 14.64 inches set in 1957.

Island of Hawaii: [August 2012 map] [Year-to-date map]

Once again, windward gages showed a near to above average frequency of rainfall but many sites had below average monthly totals.  Interestingly, several of the Kohala gages have continued to show above average rainfall totals, such as the USGS’ gage at Kawainui Stream (21.34 inches, 239 percent of average).  July had similar results.  Meanwhile, gages in the leeward areas turned in mainly below average totals.  The main exception was the Kona coffee belt region where the daily rainfall frequency and monthly totals were near the average.

Most of the windward Big Island gages had near to below average rainfall totals for 2012 through the end of August.  Most of the leeward gages remained below 50 percent of average.  The rain gage at Kawainui Stream had the highest year-to-date total of 140.67 inches (140 percent of average), which was third highest statewide.

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