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November 2013 Precipitation Summary
State of Hawaii
MONTH: November 2013
PREPARED: December 5, 2013
Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.
State: [Text data table for rain gages]
November is historically the month with the highest frequency of flash flood events in the State of Hawaii. While there have been more active months, such as November 1996, the 2013 edition managed to provide a couple of events and some close calls as well.
The most significant rain event occurred from November 7 through 10 as a complex weather pattern involving a weak surface trough, a shear line, and an upper level low pressure system affected the main Hawaiian Islands. A weak surface trough near Oahu and an upper level low north of the state helped initiate the event with a round of heavy showers over the windward slopes of the Koolau Range and to a lesser extent along the windward slopes of Kauai. Water levels in several stream became elevated but there were no reports of significant problems. A more vigorous round of heavy rainfall, this time along a low level shear line, moved over Kauai and Oahu on November 9. Heavy rainfall over Kauai’s windward slopes resulted in several surges of flow within the Hanalei River, the largest of which resulted in the closure of Kuhio Highway near the Hanalei Bridge for several hours. Oahu rainfall, in the range of 4 to 9 inches, produced elevated stream levels in several areas. Flash flooding in Waikane Stream put up to 1.5 feet of water over Kamehameha Highway and also caused some property inundation. The shear line pushed southward into Maui County and the Big Island on November 10, producing heavy showers along the northeast-facing slopes and flood-related damages in Kahului, Maui. Rainfall totals of 3 to 6 inches along the Hamakua District did not produce any notable flooding problems.
After the shear line dissipated east of the Big Island, a shift in the weather pattern brought the remnant cloud band westward back across the state on November 14 and 15. While this system threatened to produce heavy rainfall over the islands, the strongest rainfall cores remained offshore, especially west of the Big Island, and most of the totals recorded were less than one inch.
The month ended with a cold front and strong upper level trough threatening the west half of the island chain. Thunderstorms and heavy showers moving over Kauai and Oahu from the south dropped up to an inch of rain and produced minor flooding. This was followed by a stronger band of thunderstorms which moved into Kauai from the west late on November 30 and produced flash flooding in the Hanalei River and Kapaa Stream on December 1. Additional details will be provided in the December summary which will be issued in early January 2014.
Island of Kauai : [November 2013 map] [year-to-date map]
Most of the gages on Kauai posted near to above average rainfall totals for the month of November. The highest monthly total of 30.54 inches (81 percent of average) came from the U.S. Geological Survey’s (USGS) Mount Waialeale gage. This site also had the highest daily total of 9.24 inches during the shear line passage on November 9 with a peak 1-hour accumulation of 1.40 inches between 3 PM and 4 PM HST.
Most of the rainfall totals for 2013 through the end of November remained in the near average range. Mount Waialeale has recorded 297.89 inches (82 percent of average) and had the highest year-to-date rainfall total in the state.
Island of Oahu: [November 2013 map] [year-to-date map]
Most of the gages along the windward slopes of the Koolau Range had above average rainfall totals for the month of November while the rest of the island had mostly near average totals. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage had the highest monthly total of 27.82 inches (128 percent of average) and the highest daily total of 8.47 inches on November 9. Several sites along the windward slopes of the Koolau Range had their wettest November since 2007.
Most of the rainfall totals on Oahu for 2013 through the end of November were in the near average range. The Oahu Forest NWR gage had the highest year-to-date total of 206.14 inches (102 percent of average), which was third highest in the state but only barely below Puu Kukui’s second place total of 208.72 inches.
Maui County: [Maui November 2013 map] [year-to-date map] [Molokai/Lanai November 2013 map] [year-to-date map]
Most of the gages in Maui County posted below average rainfall totals for November. Kahului Airport and Puu Alii (Molokai) recorded above average rainfall. The Kahului Airport total of 4.64 inches (211 percent of average) was the highest November total at this location since 1996. Out of this monthly total, 3.55 inches occurred during the November 10 flash flood event described earlier. The USGS’ Puu Kukui gage had the highest monthly total of 18.72 inches (62 percent of average) and the highest daily total of 10.37 inches on November 10.
A majority of the gages in Maui County have recorded below average rainfall for 2013 through the end of November. Puu Kukui’s year-to-date total of 208.72 inches (62 percent of average) was the highest in the county and the second highest in the state.
Island of Hawaii: [November 2013 map] [year-to-date map]
Most of the gages on the Big Island logged below average rainfall totals for the month of November. Many of the totals were below 50 percent of the November average. The highest monthly total of 11.87 inches (74 percent of average) came from the Natural Resources Conservation Service’s (NRCS) Island Dairy gage. This rain gage also registered the highest daily total of 5.77 inches during the November 10 shear line passage. The gage at Honokaa recorded 10.20 inches (100 percent of average), which marked the highest November rainfall total since 2004.
Most of the gages on the Big Island have had below average rainfall totals for 2013 through the end of November. The USGS gage at Kawainui Stream has recorded 113.31 inches (93 percent of average), the highest year-to-date total in the county but only the ninth 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