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November 2012 Precipitation Summary
State of Hawaii
MONTH: November 2012
PREPARED: December 5, 2012
Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.
State: [Text data table for rain gages]
The 2012 – 2013 wet season is now two months overdue. Through October and November, anomalous storm tracks in the North Pacific kept significant precipitation systems away from the island chain leaving stable conditions on many days. Thus, several gages in the state reported record low November rainfall totals in what is normally one of the wettest months of the year. For more details, please see the island sections below and the Record Event Report online.
The main precipitation event occurred during the Thanksgiving holiday when a low pressure system moved close to the islands from the northwest. Large scale low level winds were weak on November 22 and 23 allowing land and sea breezes to dominate the local wind patterns. With the upper level trough nearby, the air mass overlying the main Hawaiian Islands was unstable and supported brief but heavy rainfall over northeast Maui (November 22) as well as south-central Oahu and south Maui (November 23). The Oahu rainfall partially closed the H-1 freeway due to standing water and appeared to be a contributing factor in the roof collapse of the Farrington High School auditorium though an investigation is ongoing. Nickel-sized hail was also reported in the Pearl City area. Rainfall over south Maui did not cause significant damage and brought some much-needed drought relief. A very weak cold front reached the islands with very little accompanying rainfall on November 25 to close out this event.
Most of the days before and after the Thanksgiving weekend involved trade winds in the moderate to fresh range with low daily rainfall totals. Enhanced trade wind rainfall occurred from November 15 through 17 which brought needed rainfall to the windward slopes but largely left leeward areas dry. Peak daily totals during this 3-day period were in the range of 1 to 4 inches at a few of the normally wet upslope gages.
Island of Kauai : [November 2012 map] [Year-to-date map]
All of the gages on Kauai recorded monthly totals below 50 percent of average for the month of November. The U.S. Geological Survey’s (USGS) Mount Waialeale gage recorded 11.30 inches (30 percent of average) which was the lowest November total since the record-setting 9.85 inches in 1976. November rainfall records were broken or tied at Kapahi, Kokee, Lihue Airport, the Wailua UH Experiment Station, and Wainiha. The Lihue Airport and Wainiha records are especially noteworthy since the periods of record for these sites go back to 1950 and 1949, respectively. The other sites have shorter periods of record going back to 1991.
Rainfall totals for 2012 through the end of November dropped into the below average range at several sites. Despite several months of dry conditions, there were several gages still showing near average year-to-date totals due to wet conditions early in the year. Mount Waialeale’s 302.27 inches (83 percent of average) leads all 2012 totals statewide.
Island of Oahu: [November 2012 map] [Year-to-date map]
All of the gages on Oahu reported below average rainfall totals for November with most at less than 50 percent of average. A total of 15 sites broke or tied records for the lowest November rainfall, some by a significant margin. The Lyon Arboretum gage in Manoa recorded the highest monthly total of 5.70 inches (38 percent of average). However, the island’s highest daily total of 1.80 inches came from the U.S. Fish and Wildlife Service’s (USFWS) Waiawa PHB gage during the strong thunderstorm event on November 23. This entire 24-hour total occurred between 2 PM and 4 PM HST.
Most of the gages on the island of Oahu had below average totals for 2012 through the end of November. The USFWS’ Oahu Forest National Wildlife Refuge gage had the highest year-to-date total of 149.95 inches (74 percent of average) which was fourth highest in the state.
Maui County: [Maui November 2012 map] [Year-to-date map] [Molokai/Lanai November 2012 map] [Year-to-date map]
All of the Maui County gages recorded below average rainfall for the month of November. Gages at the Kula Branch Station, Lahainaluna, Mahinahina, and Waikapu broke or tied records for the lowest November rainfall. The USGS’ Puu Kukui gage had the highest monthly total of 12.25 inches (41 percent of average) and the highest daily total of 3.81 inches during enhanced trade wind showers on November 15. Heavy afternoon showers over south Maui on November 23 brought over 2 inches of rainfall just east of the Ulupalakua Ranch headquarters.
Rainfall totals for 2012 through the end of November were below average at all of the available gages in Maui County with most totals below 50 percent of average. Puu Kukui’s 238.68 inches (71 percent of average) remained as the highest year-to-date total in the county and was second highest in the state.
Island of Hawaii: [November 2012 map] [Year-to-date map]
Most of the gages on the Big Island recorded monthly totals below 50 percent of the November average. The USGS gage at Kawainui Stream was one of the big exceptions and had the highest monthly total of 10.56 inches (131 percent of average). However, the highest daily total came from the Kealakomo gage on the Puna coast with 2.09 inches measured on November 22 during a period of moist southeasterly winds and unstable upper level conditions. Hilo Airport had a near normal count of 22 days with measurable rainfall but its monthly total of 5.52 inches was only 36 percent of average indicating a well below average amount of rain per day.
Most of the Big Island gages showed below average rainfall totals for 2012 through the end of November. The Kawainui Stream gage had the highest total of 171.63 inches (141 percent of average) and remained 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