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January 2012 Precipitation Summary
State of Hawaii
MONTH: January 2012
PREPARED: February 3, 2012
Amended on February 8, 2012 due to erroneous rainfall total for Kahului Airport
Note: This summary includes for the first time data from several automated gages operated by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS). These gages are part of the Soil Climate Analysis Network (SCAN) and are located on the Big Island. The sites are named Waimea Plain (WPLH1), Island Dairy (ILDH1), Pua Akala (PKLH1), Silversword (SLVH1), and Kainaliu (KXXH1).
State: [Text data table for rain gages]
Following two months of unseasonably persistent trade winds, the new year brought several breaks in the trade wind pattern and even 5 consecutive days of south to southwest winds. However, the change in weather pattern did not translate to more rainfall as north Pacific low pressure systems mostly stayed far away from the island chain. As a result, most areas of the state had dry conditions throughout the month with the exception of Kauai. Most of the Garden Isle’s rainfall occurred on January 17 from a band of heavy showers and thunderstorms that developed in the converging low level southerly and southwesterly winds. The rainfall was heavy enough to cause flash flooding in Hanalei River which forced the closing of Kuhio Highway at the Hanalei Bridge for several hours. Flash flooding also closed a road in Keapana Valley near Kealia in the northeast portion of Kauai. On the previous day, moist southeasterly low level winds helped produce brief periods of moderate to heavy rainfall over the southeast-facing slopes and coastal areas of the Puna and Kau Districts on the Big Island. No significant flooding problems were reported from this area of showers.
Heavy rainfall occurred again the following week, this time on the windward slopes of the Koolau Range on Oahu. This event was more localized and short-lived than the Kauai event with only minor flooding problems from the 1 to 2 inches of rainfall in the Waikane and Waiahole areas of the island.
Despite being in the heart of the cool season, there was only one cold front that reached the main Hawaiian Islands. On January 13, this front swept across the state and brought cooler temperatures for a couple of days but produced very little rainfall. The month of January usually includes 4 to 6 cold fronts of various intensities reaching at least one of the main islands in the state.
Island of Kauai : [January 2012 map]
The rain band that moved over Kauai on January 17 helped push monthly totals to near normal levels at many locations island-wide. The highest monthly total was 19.19 inches (77 percent of normal) from the U.S. Geological Survey’s (USGS) Mount Waialeale gage. Of this total, 10.13 inches fell on January 17, the day of the Hanalei River flash flood.
Island of Oahu: [January 2012 map]
Most of the rain gages on Oahu recorded below normal rainfall totals for the month of January. Many of these sites had less than 20 percent of normal rainfall. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage had the highest monthly total of 4.13 inches but this was just 24 percent of normal). The highest daily total of 1.95 inches was posted on January 24 by the USGS’ rain gage at Waiahole Stream. Several gages from Kaneohe to Kaaawa reported 1 to 2 inches of rain from this event.
Maui County: [Maui January 2012 map] [Molokai/Lanai January 2012 map]
Extremely dry conditions occurred over Maui County with most of the gages reporting less than 10 percent of normal rainfall for the month of January. Puu Kukui’s 3.50 inches (11 percent of normal) marked the lowest January rainfall total since 1998. The dry conditions made an initial report of zero measurable rainfall at Kahului Airport believable and it was initially thought that a new record for the driest January had been set for the site. However, a cold front with a solid line of rainfall swept across the state on February 8 with no rainfall measured by the airport’s precipitation sensor. This was an obvious indication that the Kahului Airport precipitation gage was not functioning properly after all.
Island of Hawaii: [January 2012 map]
In December 2011, there were 11 sites with monthly totals greater than 20 inches. In January 2012, none of the gages on the Big Island received 10 inches of rain and more than half did not record an inch. The highest monthly total was from the Kealakomo gage on the southeast coast of the Puna District. This gage recorded 8.86 inches (121 percent of normal) of which 5.56 inches fell on January 16 in moist southeasterly low level winds.
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