Monthly Precipitation
State of Hawaii Summary

The following excerpts are taken from the NOAA NWS Honolulu Forecast Office's Monthly Precipitation Summaries.

April: Trade winds prevailed through most of April at mainly moderate levels. Trade shower activity during the first two weeks of the month brought daily rainfall to the east-facing slopes of the islands, though totals were mostly less than an inch and no significant flooding problems occurred. The airmass over the island chain stabilized for the period from April 15 to 25 with many sites reporting little or no rainfall. The trades broke down on April 26 as a weak, late-season cold front moved slowly across the state on April 27 and 28 before dissipating near the Big Island and Maui on April 29. Most rain gages recorded less than a quarter of an inch during the frontal passage.

May: Trade winds prevailed through most of May though at lighter than normal levels. A weak, out-of-season shear line moved across the island chain on May 18 and 19 bringing needed rains to the windward slopes. Its remains lingered near the Big Island on May 20 before returning westward over Maui County and Oahu in the trade winds. Enough rain fell over windward Oahu from Kailua to Hauula to produce elevated stream levels and minor flooding. Upper level troughs near the state produced sufficient instability to generate heavy afternoon showers over the leeward and interior sections of the islands on May 9 and May 22 through 24. The rainfall over Upcountry Maui proved to be heavy enough to warrant advisory issuances for minor flooding on May 9 and 24.

June: Moderate trade winds dominated the weather pattern over the Hawaiian Islands during most of June. A short period of fresh to strong trade winds prompted the issuance of a wind advisory for central Maui, south Big Island, and the summits of Mauna Kea, Mauna Loa, and Haleakala on June 9 to 11. Shower areas embedded within the trades brought much needed rains to the east facing slopes of the Big Island and Maui. Drier than normal conditions during April and May over the east half of the state have been stressing water supplies, especially those on catchment systems and growers of non-irrigated crops.

No significant flood events occurred during the month though brief heavy rains over Kailua-Kona produced minor street flooding during the night of June 4. An out of season shear line on June 19 and 20 followed by an upper level trough on June 21 through 24 produced enhanced shower activity but no associated flooding problems.

Kevin R. Kodama, Senior Service Hydrologist
National Weather Service Forecast Office, Honolulu, Hawaii