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Chris O'Connor and Dr. Pao-Shin Chu
Hawaii State Climate Office
Department of Meteorology
University of Hawaii
Honolulu, HI 96822

After a record breaking two previous months of dryness, December 2012 experienced a continued trend of significantly drier than normal conditions in most locations, while other parts of the state received closer to normal levels of rainfall. This dry trend was present throughout the entire summer and autumn seasons and has now shown strong into the beginning of the winter season. Honolulu experienced record breaking dryness for the month of December (0.7% of normal rainfall amount). Oahu and Maui islands saw rainfall which was less than only 7% that of the normal amounts we see in December. Hilo and Lihue saw a consistent trend of rainfall all month, and experienced close to normal precipitation. As a result of the increase in precipitation, drought conditions across the state have improved from previous months in most areas. Oahu and Kauai currently range from "Abnormally Dry" (D0) to "Severe Drought" (D2), while the eastern islands have areas ranging from "Abnormally Dry" (D0) to "Extreme Drought" (D3) on a scale of D0-D4. The improvements occurred in northern Kauai, northeastern Oahu, northeastern Maui, and northeastern Hawai’i, where drought conditions have disappeared and moisture levels are back to normal. The big picture: we are precipitation starved at the moment; however conditions have been slightly improving!

Across the state, mean temperatures as well as mean highs and mean lows were above their respective historical averages for the first time in six months.

The NOAA Climate Prediction Center seasonal outlook for Hawaii predicted below normal temperatures and an equal chance for above, average, and below normal precipitation and for the entire state in December 2012. 

Fall 2012 has been a time of uncertainty in regards to ENSO. Initial reports dating back to the summer pointed towards an El Nino development for the 2012-13 winter season. However the past few months have brought along the development of ENSO neutral conditions. As of the end of December, the ENSO Alert System Status is “not active”, and ENSO-neutral conditions continue. Equatorial sea surface temperatures are near average across most of the Pacific Ocean. The atmospheric circulation over the tropical Pacific is near average. The general consensus is that ENSO-neutral is favored for the Northern Hemisphere winter 2012-13 and into spring 2013.

The 2012-2013 "wet season" began this past month with more than half of the state in drought. We ended December better than coming into the month, as we saw an improvement in precipitation throughout most of the state. Hawai'i still needs significant precipitation to pull out of the current drought conditions.

On a different note, Hawai’i experienced a couple weeks in December with reduced trade winds. These conditions brought heavy vog to most of the state, and concern spread state-wide amongst the affected regions of the increased vog. With vog comes a muggy and humid climate. Most people have a hard time working outside and fall short of breath when undergoing strenuous physical activity. Pharmacies around the state had to stock up on supplies to combat itchy eyes and breathing problems. Additional scare surrounded Honolulu because the vog conditions were persistent through the Honolulu Marathon race. Race officials were well prepared for the race day with plenty of water, sponges, a mist station and a full medical team, in case runners got into trouble on the course.