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Pacific ENSO Update

3rd Quarter, 2009 Vol. 15 No. 3


HI Flag State of Hawaii
Seasonal Precipitation Summary

The first half of April included trade winds with daily rainfall recorded along the windward slopes of the Hawaiian Islands. An upper level trough brought enhanced shower activity to the western half of the state on April 9 – 11. Heavy showers over the windward slopes of Oahu on April 10 produced minor flooding, with gages recording 24-hour totals of 1 to 3 inches. A shift in the central North Pacific weather pattern during the second half of April brought winter-like conditions to the Hawaiian Islands, including snowfall over the summits of Mauna Kea and Mauna Loa, and weak to non-existent trade winds. A cold front on April 20 – 21 produced 2 to 5 inches of rainfall in various areas of the state and minor flooding problems on Kauai, Oahu, Molokai, and Maui. Unstable conditions helped boost rainfall totals with more than 8 inches in 24 hours recorded at West Wailuaiki in east Maui. No significant flooding problems were associated with this rainfall event, and many locations throughout the State of Hawaii finished the month with near to below normal totals.

The unusual winter-like weather pattern over the central North Pacific continued during May. However, this did not translate to increased rainfall over the Hawaiian Islands. Normally one of the wettest locations in the world, the U.S. Geological Survey (USGS) gage on Mount Waialeale recorded only 1.51 inches (4% of normal) for the month, unofficially marking the driest May on record at this site. Conversely, the Pali 2 gage located in the Kau Desert of the Big Island recorded the state’s highest monthly total of 5.94 inches (540% of normal), surpassing the combined totals from Mount Waialeale and Puu Kukui – normally the two wettest spots in the state. An unusually late cold front passage on May 17 and 18 produced 1 to 3 inches of rain over windward Oahu and lesser amounts over the rest of thestate. A surface trough lingering near Kauai and Oahu helped trigger isolated heavy showers on both islands from May 26 – 28 but caused no significant flooding issues.

The weather pattern during the month of June appeared to be more typical of the warm season as trade winds dominated conditions over and around the Hawaiian Islands. There were no heavy rain events in June, but the resumption of trades brought much needed rainfall to windward areas of the state. Leeward areas, especially on Maui and the Big Island, did not receive much rainfall and remain under drought conditions. On June 25, the Maui County Board of Water Supply requested a 5 percent voluntary cut-back on water use for Upcountry Maui residents due to diminishing reservoir water levels. Pasture conditions have also been deteriorating on portions of all the islands and impacts to livestock operations have been increasing.

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, 2nd Quarter 2009

Station  
April
May
June
2nd Qtr
1st Half
Lihue Airport
Rainfall (inches)
2.56
0.29
0.54
3.39
8.94
% of Normal
85%
10%
30%
44%
47%
Honolulu Airport
Rainfall (inches)
0.55
0.15
0.04
0.74
6.93
% of Normal
50%
19%
9%
32%
75%
Kahului Airport
Rainfall (inches)
1.42
0.01
0.14
1.57
8.60
% of Normal
81%
2%
61%
59%
78%
Hilo Airport
Rainfall (inches)
11.38
2.13
5.37
18.88
67.24
% of Normal
91%
26%
73%
68%
110%


Climate Outlook: For Hawaii, El Niño typically brings below average rainfall to the islands during the usually wet winter months. El Niño conditions may also produce more frequent and larger episodes of high surf, mainly along north and west facing shores, during the winter months.

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

“NCEP models predict a tendency for above normal temperature for Hawaii from August-September-October to October-November December 2009, and below normal temperature for Hawaii from December-January-February to February-March-April 2010. Below median precipitation for Hawaii is expected from December-January-February to January-February-March 2010 based on the El Niño composite.”



Pacific ENSO Applications Climate (PEAC) Center
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2525 Correa Road, suite 250
Honolulu, HI 96822
(808) 956-2324

Web Master's email: peac@noaa.gov
Page Last Modified: June 01 2010 22:10:29 GMT

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