February 2017 Precipitation Summary

State of Hawaii

MONTH: February 2017

PREPARED: March 7, 2017

Note:  This summary uses the arithmetic mean, or average, for “normal” rainfall values.

State: [Text data table for rain gages]

Large rainfall fluctuations in the 2016-2017 Hawaiian Islands wet season (October through April) continued in February. Following a very dry January, many areas of the main Hawaiian Islands fell under wet conditions and near to above average rainfall. The first three weeks of the month saw a progressive and energetic North Pacific weather pattern push cold fronts across the island chain on February 6, 11, 15, and 18. The cold front on February 6 dropped 1 to 3 inches of rain from Kauai to Maui County which produced isolated minor flooding problems on the islands of Oahu and Maui. The bigger story from this event was the strong southwest winds which knocked out electricity to over 25,000 residents in the Kailua and Kaneohe areas of Oahu. The February 11 front was accompanied by much better upper level support which enhanced rainfall as the frontal band traversed Oahu. Heavy rain totaling 3 to 7 inches produced a mudslide on Diamond Head Road, deep road flooding on Kalia Street in Waikiki, and road flooding in Waimanalo. Significant rainfall also occurred on leeward sections of Maui which caused the closure of South Kihei Road between Wailana Place and Kaonoulu Street. The cold fronts on February 15 and 18 were weak with rainfall totals roughly an inch or less across the state and no flooding problems.

Trade winds resumed after the February 18 frontal passage with intensities mainly in the moderate to occasionally strong levels. These conditions persisted for about a week, then yielded to a low pressure system which developed in response to a strong short wave trough in the upper level westerlies. On February 27, the initial wave of heavy rainfall from this weather system resulted in minor flooding on Oahu and Kauai, and significant road flooding in the Makawao area of Maui. This was followed by strong thunderstorms on the evening of February 28 over the northern slopes of Oahu’s Koolau Range. While rainfall occurred from Waiahole to Kahuku, the heavy rainfall centroid was located over the slopes feeding Kamananui Stream in Waimea Valley and Kaunala Gulch above Sunset Beach. Radar rainfall estimates indicated more than 10 inches fell in less than 6 hours and the U.S. Geological Survey’s rain gage on Kamananui Stream recorded a peak 3-hour rainfall of 5.70 inches. Flash flooding caused significant damage in Waimea Valley Park with initial damage estimates running in the several tens of thousands of dollars. Flooding also closed Kamehameha Highway near Sunset Beach. Periods of heavy rainfall on Kauai that started on the afternoon of February 28 extended into the early morning hours of March 1 and eventually forced the closure of Kuhio Highway near the Hanalei Bridge.

Island of Kauai : [February 2017 map] [year-to-date map]

February rainfall totals from the island of Kauai were in the near to above average range at most of the sites. The highest percent of average values came from the leeward gages but conditions weren’t as wet as February 2012 and February 2014. The U.S. Geological Survey’s (USGS) Mount Waialeale gage had the highest monthly total of 21.84 inches (89 percent of average) and the highest daily total of 7.27 inches on February 28. Lihue Airport’s 6.28 inches (199 percent of average) marked its wettest month since August 2015. While it was nearly double the February average, it was not close to being a February record and has been surpassed 7 times in the last 30 years.

All of the gages on Kauai have recorded near to below average rainfall totals for 2017 through the end of February. The Mount Waialeale year-to-date total of 35.49 inches (72 percent of average) was the highest on Kauai and the second highest in the state.

Island of Oahu: [February 2017 map] [year-to-date map]

Nearly all of the gages on Oahu had near to above average rainfall totals for the month of February. A few of the totals from leeward sites were very much above average. The USGS’ Poamoho No. 1 gage had the highest monthly total of 18.69 inches (119 percent of average). Their Kamananui rain gage had the highest daily total of 8.20 inches during the flash flood event on the night of February 28. The Kunia rain gage posted its highest February total in nearly 30 years, and the rain gages at Honolulu Airport, Waipio, Lualualei, Aloha Tower, and Niu Valley had their wettest February since 2004.

Despite the recent wet conditions, most of the rain gages had near to below average totals for 2017 through the end of February due to the island-wide drier than average conditions in January. The USGS’ Poamoho No. 1 Gage had the highest year-to-date total of 28.44 inches (84 percent of average).

Maui County: [Maui February 2017 map] [year-to-date map] [Molokai/Lanai February 2017 map] [year-to-date map]

Rain gages along the slopes of Haleakala had near to above average rainfall totals for the month of February. Gages on West Maui, as well as Molokai and Lanai, had near to below average totals. The USGS’ rain gage at West Wailuaiki Stream had the highest monthly total of 14.36 inches (97 percent of average) and the highest daily total of 5.76 inches on February 28.

Nearly all of the gages across Maui County had near to below average rainfall totals for 2017 through the end of February. The USGS’ West Wailuaiki gage had the highest year-to-date total of 32.10 inches (92 percent of average) which was third highest in the state. Although there were wet conditions in some areas of the county, the very dry conditions in January put the rainfall totals deep into deficit territory to start the new year.

Island of Hawaii: [February 2017 map] [year-to-date map]

Most of the gages on the Big Island recorded below average rainfall totals for the month of February. Many of the totals from the Kau, Kona, and leeward Kohala areas of the island had totals that were below 50 percent of the February average. The USGS’ Saddle Road Quarry rain gage had the highest monthly total of 11.26 inches (109 percent of average) and the highest daily total of 2.62 inches on February 27. The 3.11 inches (20 percent of average) observed by the Glenwood gage marked the lowest February total at this site since 2000.

All of the leeward Big Island gages had below average rainfall for 2017 through the end of February. For the windward areas, most of the year-to-date totals were in the below average range though there were a few sites with near to above average amounts. The USGS’ Saddle Road Quarry gage had the highest year-to-date total of 43.06 inches (207 percent of average), which was also the 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