April 2016 Precipitation Summary

State of Hawaii

MONTH: April 2016

PREPARED: May 4, 2016

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

State: [Text data table for rain gages]

The 2015-2016 Hawaiian Islands wet season ended with the establishment of almost continuous trade winds across the state with intensities mostly in the moderate to fresh range. A couple of weak cold fronts produced brief disruptions in trades on April 5 through 6 and on April 16 through 17. As often happens with these weak frontal systems, the moist northerly winds brought enhanced rainfall to northwestern Kauai which made Hanakapiai Stream impassable on the popular Na Pali Coast trail. The swollen stream stranded 15 to 20 hikers in both events but no one was injured. In north Kona, localized early morning showers produced minor flooding but no reports of any damage on April 5, a day before the cold front’s arrival on the Big Island.

While the trade winds brought abundant rainfall to the windward slopes, the leeward areas remained rather dry and under drought conditions. As the dry season begins for most of the island chain, the probability of drought recovery over the next several months is rather low. Additional details on drought conditions can be found on the U.S. Drought Monitor website at http://droughtmonitor.unl.edu and in the Drought Information Statement issued by the Weather Forecast Office Honolulu at http://www.weather.gov/data/HFO/DGTHFO.

Island of Kauai : [April 2016 map] [year-to-date map]

Many windward locations reported near to above average rainfall during the month of April while most leeward totals were below average. The highest monthly total of 37.70 inches (100 percent of average) came from the U.S. Geological Survey’s (USGS) Mount Waialeale gage. Another USGS site, Kilohana on the northwestern side of the island, had the highest daily total of 5.62 inches on April 16. In contrast to the wet conditions at Kilohana, the gage at Kalaheo had its lowest April total since 1992.

Rainfall totals for 2016 through the end of April were below average at most of the gages on Kauai. Mount Waialeale passed Kilohana with the highest year-to-date total on the island at 71.59 inches (57 percent of average). Most of the other locations had year-to-date totals in the 30 to 70 percent of average range.

Island of Oahu: [April 2016 map] [year-to-date map]

Gages along the windward and leeward interior slopes of the Koolau Range had rainfall totals mainly in the near to above average range for the month of April. Many of the lower elevation leeward sites had monthly totals at less than 50 percent of average. The highest monthly total was from the Manoa Lyon Arboretum gage with 17.64 inches (125 percent of average). This location also had the highest daily total of 5.00 inches during the weak cold front passage on April 17. The Aloha Tower rain gage had its lowest April total since 2006.

All of the gages on Oahu had below average rainfall totals for 2016 through the end of April with most amounts at less than 50 percent of average. The USGS’ Poamoho No. 1 rain gage had the highest year-to-date total of 35.18 inches (46 percent of average).

Maui County: [Maui April 2016 map] [year-to-date map] [Molokai/Lanai April 2016 map] [year-to-date map]

Windward Haleakala and windward Molokai rainfall totals for the month of April were in the near to above average range but totals for most of the remaining sites across Maui County were below average. Abundant showers embedded within the trade wind flow and enhanced on the slopes produced a monthly total of 42.55 inches (169 percent of average) at the USGS’ West Wailuaiki rain gage. In addition to the highest monthly total this site recorded a 2-day total of 14.11 inches on April 6 and 7, and more than an inch of rain on 12 days during the month. The Mahinahina gage posted its highest April total in a data record going back to 1991. This site is exposed to trade wind showers spilling over the crest line of the West Maui Mountains.

Most of the gages across Maui County had below average rainfall totals for 2016 through the end of April. The West Wailuaiki gage on east Maui had the highest year-to-date total with 78.23 inches (88 percent of average).

Island of Hawaii: [April 2016 map] [year-to-date map]

Monthly rainfall totals were in the near to above average range at most of the gages along the windward slopes and a portion of the slopes in the South Kona District of the Big Island. The highest monthly total of 42.76 inches (293 percent of average) was from the USGS’ Saddle Quarry gage. This site received more than an inch of rain on 17 days during April. The highest daily total of 7.81 inches came from the USGS’ rain gage at Kawainui Stream during the cold front passage on April 6. This was part of a 2-day total of 13.94 inches on April 6 and 7. In contrast, Kapapala Ranch on the southeastern flank of the Big Island posted its lowest April rainfall total since 2006.

Rainfall totals for 2016 through the end of April were in the below average range at most of the gages on the Big Island. The Saddle Quarry gage had the highest year-to-date total of 71.20 inches (139 percent of average). Most of the remaining Big Island totals were below 50 percent of average.

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