Special to Hawaii 247 by Kevin R. Kodama | NOAA/NWS Senior Hydrologist

Although trade winds dominated the lower level weather pattern, upper level low pressure systems helped create an unusually unstable airmass over the island chain. This resulted in wetter than normal conditions in many areas of the state during the month of June.

The main precipitation events of the month happened June 1-4 as a strong upper level low pressure system moved over the main Hawaiian Islands. Very unstable conditions produced intense thunderstorms with an unusually high amount of lightning activity.

During a 70-hour period from 3 p.m. June 2 through 1 p.m. June 5, lightning count data indicated nearly 52,000 flashes over and around the Hawaiian Islands. In addition, heavy rainfall in the range of 2 to 4 inches caused flash flooding which closed Kamehameha Highway at Waikane Stream and Kapaa Quarry Road near Kawainui Marsh.

The airmass stabilized with mostly moderate to fresh trade winds dominating the weather pattern over the state for the remainder of the month. Daily rainfall occurred along windward slopes but there were no additional significant flood events.

Island of Hawaii:

Most of the windward Big Island gages had near to above normal rainfall totals for the month of June. However, most of the leeward sites had below normal totals.

The USGS’ rain gage at Kawainui Stream had the highest monthly total of 24.44 inches (209 percent of normal) and the highest daily total of 4.57 inches June 16.

Most of the Ka‘u and North/South Kona District totals were at less than 50 percent of normal. Hilo Airport had a slightly higher than normal number of days with measurable rainfall (at least 0.01 inches), but the average amount of rain per day was below normal.

Most of the Big Island rainfall totals for 2011 through the end of June fell within the below normal range. The rain gage at Kawainui Stream had the highest year-to-date total of 69.74 inches (81 percent of normal), surpassing Glenwood’s 68.67 inches. Most of the Big Island totals were in the range of 40 to 70 percent of normal.

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 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, and the U.S. Fish and Wildlife Service. Data presented here are not certified and should be used for information purposes only.

— Find out more:
www.prh.noaa.gov/hnl/pages/hydrology.php