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January 2013 Precipitation Summary
State of Hawaii
MONTH: January 2013
PREPARED: February 6, 2013
Note: This summary uses the arithmetic mean, or average, for “normal” rainfall values.
State: [Text data table for rain gages]
Several weather systems during the month of January helped bring above average rainfall to portions of the State of Hawaii and some drought relief. The month started with a weak cold front moving over the west half of the state before stalling over Maui County on January 2 and 3. The stalled frontal cloud band brought enhanced showers to the windward slopes from Kauai to Maui with some of the rainfall reaching the leeward areas. Strong and at times locally damaging trade winds followed the cold front from January 4 through 7, and then weakened to the moderate to fresh range from January 8 through 11. Showers embedded in the trades kept the windward slopes rather wet. Daily totals in several spots were in the 1 to 2 inch range with a few upslope locations having totals of 6 to 9 inches. Rainfall was distributed well in time so there were no reports of significant flooding problems.
Another weak cold front reached the island chain in mid-January. The heaviest rainfall in this event occurred within a pre-frontal convergence shower band that moved over Kauai late on January 13, progressed eastward, and then stalled over the Big Island early on January 15. Several event totals hit the 1 to 2 inch range but there were no reports of flooding.
The last week of the January brought the most significant rain event of the month to the islands. This weather system involved yet another weak cold front but it did have much better upper level support which helped increase the instability of the airmass. A rain band associated with the cold front moved over Kauai from the west during the morning of January 27. A second round of heavy rainfall hit the southeast coast of the island during the early afternoon hours and flooding forced the closure of Kuai Road in Poipu. Event totals on Kauai were mostly in the 1 to 2 inch range with the highest amount of 4.19 inches coming from the Poipu gage. As the weather system shifted eastward, a pre-frontal convergence rain band moved over Oahu with heavy rainfall during the afternoon hours of January 27. Some of the most intense rainfall cores in the band had rain rates in excess of 4 inches per hour. The main cold front rain band brought a second round of heavy rainfall to Oahu a few hours later. Rainfall with rates as high as 2 to 3 inches per hour combined with the saturated ground from the earlier batch of rain resulted in flash flooding in several areas. Flood impacts on Oahu, which included road closures and property damage, occurred in Waianae, Nanakuli, Mililani, Wahiawa, Hauula, and Kaaawa. Many of the 24-hour (8 AM HST January 27 to 8 AM HST January 28) rain totals on Oahu were in the 2 to 4 inch range. Punaluu Stream had the highest 24-hour total of 5.61 inches. Molokai was next in line for heavy rain though intensities lessened somewhat. Showers mainly affected the west half of the island during the night of January 27 causing minor flooding but no reports of damage. Maui took its turn on the morning of January 28 as persistent moderate to heavy showers developed along the northeast-facing slopes. The heaviest showers occurred over the lower slopes of the West Maui Mountains from Wailuku to Kahakuloa. Flash flooding occurred along Kahekili Highway and damaged a business in Wailuku town. The Big Island was left out of the heavy rain picture as the frontal system weakened and stalled over Maui County. Most of the Big Island rainfall totals were less than an inch with the highest amount of 1.46 inches coming from the Kapapala gage in the Kau District. While the amounts were relatively small, the rainfall did bring a bit of relief to some of the drought-plagued leeward areas.
Island of Kauai : [January 2013 map]
Most of the rain gages on Kauai recorded near to above average totals for the month of January. The below average totals were mainly from the northwestern quadrant of the island. Omao and Lihue Airport both posted the highest January totals since 2002 and 2004, respectively. The U.S. Geological Survey’s (USGS) Mount Waialeale gage measured 35.72 inches (144 percent of average), which was the highest January total since 2007 at this site. Mount Waialeale also had the highest daily total of 6.35 inches during wet trade wind conditions on January 9.
Island of Oahu: [January 2013 map]
Most of the gages on Oahu reported near to above average rainfall for the month of January. West Oahu rainfall largely occurred during the mid- and late-January events whereas the Koolau Range also received a considerable amount from the early January wet trade wind rainfall. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge gage had the highest monthly total of 34.54 inches (202 percent of average) and the highest daily total of 7.21 inches on January 3. Punaluu Pump’s 14.23 inches (211 percent of average) marked the wettest January at this location since 1997.
Maui County: [Maui January 2013 map][Molokai/Lanai January 2013 map]
The Molokai Airport gage (6.62 inches) had its wettest month since March 2006, and the Makapulapai (6.76 inches) and Haiku (6.84 inches) gages recorded their highest January rainfall totals since 2004. Despite these notable amounts, most of the gages across Maui County recorded below average monthly rainfall totals. Most of the drought-plagued leeward areas had monthly totals at less than 60 percent of average. The USGS’ gage on Puu Kukui had the highest monthly total of 31.69 inches and the highest daily total of 8.71 inches on January 4 in wet trade wind conditions.
Island of Hawaii: [January 2013 map]
All of the gages on the Big Island recorded near to below average rainfall for the month of January. Mountain View had the highest monthly total of 9.54 inches (67 percent of average) which included 3 days with more than an inch of rain from January 5 through 9. Kapapala Ranch had the highest daily total of 1.46 inches on January 29 and its monthly total of 5.14 inches marked the wettest January at this gage since 2007.
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