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October 2013 Precipitation Summary
State of Hawaii
MONTH: October 2013
PREPARED: November 6, 2013
Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.
State: [Text data table for rain gages]
The first month of the 2013 – 2014 wet season began with a continuation of a heavy rain event that initiated over Kauai and Oahu on September 30. This event involved an upper level low pressure system, one of several in October, that prompted flash flood warnings due to rapidly rising water in Hanalei River. Calmer conditions returned on October 2 with the resumption of moderate trade winds and generally light showers focused on the windward slopes through October 10. In addition to the September 30 – October 1 event, upper level low pressure systems also influenced local weather conditions to varying degrees from October 11 through17 and on October 26 through 27. These events mainly involved the development of localized heavy showers and some thunderstorms in the afternoon hours over most of the islands.
The most active day was October 14 when strong thunderstorms developed over west Oahu and produced intense rainfall, small hail over Mililani, and a waterspout off the Nanakuli coast. Rainfall totals on Oahu were in the 1 to 3 inch range with some minor road and small stream flooding. Honouliuli Stream in Ewa and Waikele Stream in Waipahu almost overflowed their banks but ultimately remained within their existing channels. October 27 was another intense rain day as thunderstorms developed over numerous areas of Oahu. Rain gages and radar estimates indicated rates in excess of 3 to 4 inches per hour in some spots. Fortunately the heavy rain cores did not persist over any particular location for a prolonged period so flood-related impacts were relatively minor.
While these events produced some exciting weather displays, the coverage of rainfall was spotty and brief, and the days outside of these events were relatively dry in most areas. Even the passage of a weak cold front over Kauai and Oahu on October 19, the first of the wet season, was barely noticeable with peak rainfall amounts of less than an inch produced by the frontal cloud band. As a result, the monthly totals from across the state indicated that the overall conditions were on the drier side of normal.
Island of Kauai : [October 2013 map] [year-to-date map]
Most of the gages on Kauai recorded below average rainfall for the month of October. The hit-or-miss convection resulted in a few spots receiving above average rainfall, including Lihue Airport where its 7.99 inches (209 percent of average) registered as its wettest October since 1982. Most of the other sites had totals in the range of 40 to 70 percent of average. The highest monthly total, 26.38 inches (78 percent of average) came from the U.S. Geological Survey’s (USGS) gage on top of Mount Waialeale. This site also had the highest daily total of 4.87 inches on October 2.
Most of the rainfall totals for 2013 through the end of October were in the near average range. Mount Waialeale’s 267.35 inches (82 percent of average) was the highest year-to-date rainfall total in the state.
Island of Oahu: [October 2013 map] [year-to-date map]
Most of the gages on Oahu logged below average rainfall totals for the month of October. The USGS’ Poamoho Rain Gage No. 1 had the highest monthly total of 13.12 inches (67 percent of average) while the gage at Hakipuu Mauka had the highest daily total of 4.55 inches on October 11. This one-day amount at Hakipuu Mauka accounted for more than half of its monthly total and helped push it into the above average range. The Hawaii Kai Golf Course total of 0.19 inches (9 percent of average) marked the driest October at this location since 1994.
Most of the rainfall totals for 2013 through the end of October remained in the near average range. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge gage had the highest year-to-date total of 178.32 inches (99 percent of average), which was third highest in the state.
Maui County: [Maui October 2013 map] [year-to-date map] [Molokai/Lanai October 2013 map] [year-to-date map]
Most of the gages in Maui County reported below average rainfall totals for the month of October, with more than half of the totals at less than 30 percent of average. While the USGS’ Puu Kukui gage recorded the highest monthly total of 9.64 inches, this was only 37 percent of its October average. The 0.17 inches from the Molokai Airport gage registered as its driest October since 1994 and the third driest October on record.
Maui County rain gages have logged near to below average rainfall totals for 2013 through the end of October. Puu Kukui’s year-to-date total of 190.00 inches (62 percent of average) was the highest in the county and second highest in the state.
Island of Hawaii: [October 2013 map] [year-to-date map]
Most of the gages on the Big Island recorded below average rainfall for the month of October. The highest monthly total of 8.51 inches (73 percent of average) came from the Pahoa gage, an unusual distinction for this site. Kapapala Ranch had the highest daily total of 1.65 inches on October 16. The Kohala region of the island was exceptionally dry with records for the driest October broken at the Kamuela and Kahua Ranch sites. Kamuela Upper had its driest October since 2003. Afternoon showers and some periods of moist southeast low level winds resulted in Kapapala Ranch and Pahala having their wettest October since 2006.
Most of the gages on the Big Island have recorded below average rainfall totals for 2013 through the end of October. The USGS gage at Kawainui Stream had the highest year-to-date total of 104.23 inches (92 percent of average) which was eighth 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 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