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Pacific ENSO Update

2nd Quarter, 2009 Vol. 15 No. 2

HI Flag State of Hawaii
Seasonal Precipitation Summary

The first week of 2009 began with a very wet weather pattern, bringing heavy rainfall to portions of Kauai, Niihau, Oahu, and the Big Island. During the second week of January, north Pacific weather transitioned to a more progressive pattern, with a series of quick cold front passages producing brief periods of heavy rains and cool temperatures across the island chain. The cold front on January 16 was the most active, featuring a single 24-hour total of 9.74 inches at Kaupo Gap on the southeast slope of Haleakala, Maui. Minor flooding problems accompanied these fronts but no significant damages occurred. While the passage of the cold fronts helped eliminate drought areas on Kauai and Oahu, significant areas of drought continued to persist over the leeward sections of the Big Island and Maui County.

February started with a weak shear line pushing across the island chain on February 1 and 2 before stalling just east of the Big Island. This shear line produced the most significant rainfall of the month including 4 to 7 inch totals over the windward slopes of Maui and the Big Island. On February 7, a brief break in the trades allowed local land and sea breezes to occur with deep convection forming over west Oahu and the Big Island interior. Short-lived heavy showers produced minor flooding and even quarter-inch hail. Moderate trades returned on February 8 and 9 only to weaken once again as a strong upper level trough affected island weather from February 10 to 12. Heavy afternoon showers and thunderstorms occurred on all 3 days with the Kapolei area of Oahu and the South Kohala District of the Big Island seeing the strongest activity. The Kapolei thunderstorm produced brief but intense rainfall that prompted a flash flood warning but did not produce significant damage. However, this thunderstorm did produce a tornado which caused property damage and some injuries. From February 13 through the end of the month, a rather strong and persistent blocking high pressure pattern became established over the north central Pacific, resulting in uninterrupted trade winds and limiting daily rainfall totals to less than 1 inch along windward slopes.

Through most of March, the weather pattern over the Hawaiian Islands involved trade winds. Two notable breaks in the trades occurred from March 7 through 9 and from March 12 through 19, both of which produced the month’s most significant rain events. On March 7, a strong upper level trough helped trigger heavy rainfall across windward areas of the state. At Hilo Airport, over 18 inches of rain in 2-days broke daily rainfall records for March 7 and 8. Flooding resulted in the closure of some secondary roads in the Hilo area but otherwise did not produce significant damages or injuries. Hanalei River on the island of Kauai briefly overflowed during the night of March 8 and into the early morning hours of March 9. Over windward Oahu, 5 to 8 inches of rain on the night of March 9 prompted the issuance of a flash flood warning and forced the closure of the Kamehameha Highway off-ramp on the H-3 Freeway. A weak cold front swept across the state on the 12th and cool air surged over the island chain from the northwest. Heavy showers and thunderstorms over Oahu and Maui County during the morning hours of March 14 prompted the issuance of a flash flood warning due to heavy rainfall in the Ewa and Kapolei areas of Oahu, but there were no reports of significant damage. Trades returned at moderate to fresh levels on March 20 and persisted through the remainder of the month. While no flooding problems occurred during this time frame, windward areas, especially on the Big Island, saw frequent shower activity during the last 2 weeks of the month.

Additional individual rainfall station information and specific island information for Hawaii can be found in the Monthly Precipitation Summaries.

Hawaii Rainfall Summary for Select Stations, 1st Quarter 2009

1st Qtr
Lihue Airport
Rainfall (inches)
% of Normal
Honolulu Airport
Rainfall (inches)
% of Normal
Kahului Airport
Rainfall (inches)
% of Normal
Hilo Airport
Rainfall (inches)
% of Normal

Climate Outlook: The following is in excerpt from the Climate Prediction Center’s official Seasonal Outlook Discussion for Hawaii ...

“NCEP models predict a tendency for below normal temperature for Hawaii from May-June July to June-July-August 2009. NCEP tools give no indication of either above or below median precipitation for Hawaii for May 2009. However, above median precipitation for Hilo is expected from August-September-October to October-November- December 2009.”

Pacific ENSO Applications Climate (PEAC) Center
c/o NOAA NWS - Weather Forecast Office Honolulu
2525 Correa Road, suite 250
Honolulu, HI 96822
(808) 956-2324

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Page Last Modified: June 01 2010 22:44:42 GMT


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