June 2017 Precipitation Summary

Monthly Precipitation Summary

State of Hawaii

Month: June 2017

Prepared: July 6, 2017

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

State: [Text data table for rain gages]

There were no significant flash flood events reported in the main Hawaiian Islands during June. This is not surprising since June historically has the lowest number of flash flood occurrences. Trade winds were uninterrupted the entire month with speeds mostly in the moderate to fresh range. A couple of remnant cold front rain bands embedded in the trades moved over the state on June 8 and June 11. The June 8 band registered only small amounts of rainfall but the June 11 band produced roughly a half to an inch of rain over the windward slopes of Oahu and Kauai, and up to 2 inches over Upcountry Maui.

A more noteworthy weather event was an upper level low pressure system that moved over the island chain on June 13 and lingered in the area through June 15. Since this was a relatively strong low pressure system for this time of the year, the atmosphere became rather unstable and triggered periods of thunderstorms and heavy rainfall across portions of the state. Minor flooding occurred on June 13 over Kauai, and on June 14 over Maui, the Big Island, and central Oahu.

Following the departure of the upper level low, unseasonably stable conditions moved over the area with the cloud-capping trade wind inversion near or below 5000 feet on several days. The trade wind inversion is normally above 7000 feet, especially during this time of year. The anomalously low inversion level restricted cloud vertical development and, thus, rainfall production statewide through the remainder of June.

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

June rainfall totals from Kauai were mostly in the near to above average range. The U.S. Geological Survey’s (USGS) Mount Waialeale gage had the highest monthly total of 38.54 inches (117 percent of average) and the highest daily total of 4.78 inches on June 14. Another USGS site, at Kilohana, recorded 16.34 inches (165 percent of average). This was the highest monthly total so far in 2017 at this site despite being in what is normally one of the driest months of the year.

Most of the rain gages on Kauai had near average rainfall totals for 2017 through the end of June. Mount Waialeale had the highest year-to-date total of 144.51 inches (77 percent of average).

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

Near to above average rainfall totals were recorded by most of the rain gages on Oahu during the month of June. The highest monthly total of 12.50 inches (105 percent of average) was recorded by the Manoa Lyon Arboretum gage. Oahu’s highest daily total was 2.68 inches at the USGS’ gage from thunderstorm activity on June 14. Poamoho Experiment Farm’s 4.78 inches was about 6 times greater than the June average of 0.79 inches and marked the wettest June at this site since 1996.

Rainfall totals for 2017 through the end of June remained in the near average range at most of the gages on Oahu. The USGS’ Poamoho No. 1 Gage had the highest year-to-date total of 79.95 inches (72 percent of average).

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

Many of the gages across Maui County had below average rainfall totals for the month of June. Most of these gages were in Maui’s central valley and on the slopes of the West Maui Mountains. The Upcountry area on Haleakala’s western slope had above average rainfall, most of which occurred during the period from June 11 through June 15 associated with the remnant cold front rain band and the previously mentioned upper level low. The USGS’ gage on top of Puu Kukui had the highest monthly total of 9.95 inches but this was only 34 percent of the long term June average. This gage also recorded the highest daily total of 2.19 inches on June 14. The Upcountry gages at Ulupalakua Ranch and Kula Branch Station posted their highest June totals since 1982 and 2004, respectively.

Despite the onset of dryness in some areas, most of the gages across Maui County had rainfall totals in the near to above average range for 2017 through the end of June. The USGS’ rain gage at West Wailuaiki Stream had the highest year-to-date total of 82.37 inches (68 percent of average).

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

June rainfall totals were in the below average range at most of the Big Island gages. The USGS’ rain gage at Kawainui Stream had the highest monthly total of 12.79 inches (130 percent of average) and the highest daily total of 2.70 inches on June 4. All of the monthly totals from the windward sites were in the below average range with Laupahoehoe having its lowest June total since 2004. Most of gages on the Kona slopes had near average June totals.

Rainfall totals for 2017 through the end of June were in the below average range at most of the gages on the Big Island. The USGS’ rain gage at Kawainui Stream had the highest available year-to-date total of 68.62 inches (88 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