July 2015 Precipitation Summary

State of Hawaii

MONTH: July 2015

PREPARED: August 10, 2015

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

State: [Text data table for rain gages]

Trade wind conditions occurred across the main Hawaiian Islands on just a little over two-thirds of the days in July 2015 versus a long term average frequency of more than 90 percent.  The breaks in the trades resulted in warm, humid conditions across the island chain fueled by sea surface temperatures at 1 to 2 degrees Celsius above average.  Higher moisture content in the lower levels of the atmosphere also helped produce wetter than average conditions in many areas though the coastal locales tended to be dry.

The most significant hydrologic event took place on Kauai during the afternoon of July 22.  Heavy rainfall enhanced by an upper level low pressure system northwest of the island chain produced flash flooding in Hanalei River which forced the closure of Kuhio Highway near the Hanalei Bridge.  The highway was closed for a brief period of time and there were no reports of injuries or significant property damage as a result of this inundation.

A wet trade wind day on July 16 resulted in minor flooding from 2 to 4 inches of rainfall along the slopes of the Koolau Range on Oahu.  This was followed the next day by a weak surface trough that produced heavy rainfall over the windward slopes of the Big Island.  There were no reports of significant flooding problems from either event.

Island of Kauai : [July 2015 map] [year-to-date map]

Rainfall totals were in the near to above average range at most of the gages on Kauai.  The U.S. Geological Survey’s (USGS) Mount Waialeale rain gage had the highest monthly total of 37.53 inches (97 percent of average) which made it the wettest July since 2000 at this site.  The highest daily total was 6.61 inches from the USGS’ North Wailua Ditch rain gage on July 22.  While many of the interior sites showed wet July conditions, the rain gage at Lihue Airport reported only 0.76 inches (41 percent of average) which checked in as the driest July since 2005.

Rainfall totals were in the near to above average range at most of the gages on Kauai.  The U.S. Geological Survey’s (USGS) Mount Waialeale rain gage had the highest monthly total of 37.53 inches (97 percent of average) which made it the wettest July since 2000 at this site.  The highest daily total was 6.61 inches from the USGS’ North Wailua Ditch rain gage on July 22.  While many of the interior sites showed wet July conditions, the rain gage at Lihue Airport reported only 0.76 inches (41 percent of average) which checked in as the driest July since 2005.

Most of the rain gages on Kauai had below average rainfall totals for 2015 through the end of July.  Mount Waialeale had the highest year-to-date total of 158.64 inches (70 percent of average).

Island of Oahu: [July 2015 map][year-to-date map]

Over half of the rain gages on Oahu recorded July rainfall totals in the near to above average range. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage had the highest monthly total of 19.60 inches (107 percent of average) while the USGS’ Poamoho Rain Gage No. 1 had the highest daily total of 3.59 inches on July 16. While wet conditions occurred over the slopes, several lowland sites indicated dry conditions, such as the Aloha Tower gage (0.28 inches, 25 percent of average) which reported its lowest July total since 2007.

All of the rainfall totals on Oahu were in the near to below average range for 2015 through the end of July. The Oahu Forest NWR gage had the highest year-to-date total of 100.33 inches (80 percent of average).

Maui County: [Maui July 2015 map] [year-to-date map] [Molokai/Lanai July 2015 map] [year-to-date map]

Most of the rain gages across Maui County checked in with near to above average monthly totals for July. The highest monthly total of 6.74 inches (124 percent of average) was from the National Park Service’s Puu Alii gage. The USGS’ Puu Kukui gage likely had a higher total but data from this site remained unavailable due to an equipment problem at this difficult to access location. The highest available daily total of 2.04 inches on July 25 was from Ulupalakua Ranch which continued to have an unusually wet summer.

Rainfall totals for 2015 through the end of July fell into the near to above average range at most of the sites across Maui County.  The highest available year-to-date total was from the Puu Alii gage on Molokai which has recorded 114.01 inches (177 percent of average).

Island of Hawaii: [July 2015 map] [year-to-date map]

More than half of the gages on the Big Island recorded July rainfall totals in the near to below average range. Several locations, mainly along the windward and southeastern slopes, indicated near to above average totals. The gage at Mountain View in the Puna District had the highest monthly total of 15.99 inches (101 percent of average) and the highest daily total of 4.10 inches on July 9.

Rainfall totals for 2015 through the end of July fell into the near to below average range at most of the gages across the Big Island. The USGS’ rain gage at Kawainui Stream had the highest year-to-date total of 118.76 inches (130 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