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August 2013 Precipitation Summary
State of Hawaii
MONTH: August 2013
PREPARED: September 4, 2013
Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.
State: [Text data table for rain gages]
Dry overall conditions in mostly moderate trade winds prevailed across the main Hawaiian Islands with several locations breaking records for the lowest August rainfall. These dry conditions occurred despite the presence of 5 tropical cyclones in the Central North Pacific basin. Out of the 5 cyclones, only the remnant of former Tropical Storm Gil moved close enough to the island chain to directly impact weather conditions. Moisture from this remnant swept westward across the state from August 9 through 11 and produced the wettest days in the entire month. Most of the rain occurred over the windward slopes with event totals in the 1 to 4 inch range with some 6 to 8 inch totals recorded by gages on the higher elevations. There were no reports of significant flooding during this enhanced rainfall period. In fact, without this boost in rainfall, many more low rainfall records would likely have fallen statewide.
Island of Kauai : [August 2013 map] [year-to-date map]
Most of the gages on Kauai recorded below average rainfall totals for the month of August. The U.S. Geological Survey’s (USGS) Mount Waialeale gage had the highest total of 17.65 inches (51 percent of average) though it was lowest August total for this site since 2005. This gage also had the highest daily total of 3.58 inches on August 11 during the passage of former Tropical Storm Gil’s remnant moisture across the island. Records for the driest August were broken at Hanapepe and Omao. Data for these sites go back to 1993 and 1995, respectively.
Despite the dry conditions, rainfall totals for 2013 through the end of August remained in the near average range at most of the gages on Kauai. Mount Waialeale’s 212.34 inches (81 percent of average) was the highest year-to-date total statewide.
Island of Oahu: [August 2013 map] [year-to-date map]
The passage of Gil’s remnant moisture over Oahu produced a tremendous contrast in rainfall conditions during the month. Enhanced rainfall from the remnant remained largely confined to the windward slopes of the Koolau Range so the affected gages from Kahuku to Hawaii Kai ended up with near to above normal monthly totals. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage recorded the highest monthly total of 16.62 inches (87 percent of average) and the highest daily total of 6.13 inches on August 10. The Waimanalo, Punaluu Pump, and Waihee Pump gages posted their highest August rainfall totals since 2004. However, very dry conditions prevailed over the rest of the island with many locations receiving less than 20 percent of average rainfall. The Mililani, Palisades, Waipio, Kunia, and Waiawa Correctional Facility gages all broke records for the lowest August rainfall totals in data sets going back to 1991.
Rainfall totals for 2013 through the end of August remained in the near normal range for most of the sites on Oahu. The Oahu Forest NWR gage had the highest year-to-date total of 153.91 inches (107 percent of average), which was third highest in the state.
Maui County: [Maui August 2013 map] [year-to-date map] [Molokai/Lanai August 2013 map] [year-to-date map]
Most of the gages across Maui County posted near to above average rainfall totals for the month thanks mainly to the passage Gil’s remnant. One notable example is Kepuni’s large 620 percent of average value off a monthly total of 3.04 inches. Of this total, 2.86 inches occurred as a result of ex-Gil’s moisture. Elsewhere in the county, the Lahainaluna and Molokai Airport gages had their highest August rainfall totals since 1995 and 2004, respectively. The USGS’ Puu Kukui gage recorded the highest monthly total of 21.00 inches (63 percent of average) and the highest daily total of 7.26 inches on August 10.
Gage totals from across Maui County were in the near to below average range for 2013 through the month of August. Puu Kukui had a year-to-date total of 169.24 inches (66 percent of average) which was second highest in the state.
Island of Hawaii: [August 2013 map] [year-to-date map]
Most of the gages on the Big Island recorded below average rainfall totals for the month of August. Windward locations received rainfall almost on a daily basis though generally in low amounts. The USGS rain gage at Kawainui Stream had the highest monthly total of 15.66 inches (175 percent of average) while the highest daily total came from Piihonua with 3.38 inches recorded on August 10. The Pahoa and Kealakekua sites, on opposite sides of the island, both had their lowest August totals in records going back to 1991 which helped illustrate the overall dryness affecting the area.
All of the Big Island gages had rainfall totals for 2013 through the end of August in the near to below average range. The rain gage at Kawainui Stream had the highest year-to-date total of 97.87 inches (98 percent of average). This was the eighth highest total statewide.
Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lihue, 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 Hawaii Department of Land and Natural Resources, the U.S. Geological Survey, the U.S. Bureau of Land Management, the U.S. National Park Service, the Department of Defense, the U.S. Fish and Wildlife Service, and the U.S. Department of Agriculture. Averages come from the National Climatic Data Center (1981-2010 series) and the Rainfall Atlas of Hawaii (http://rainfall.geography.hawaii.edu/). Data presented here are not certified and should be used for informational purposes only.
Kevin R. Kodama
Senior Service Hydrologist
NOAA/NWS Weather Forecast Office Honolulu