Hurricane Fernanda was one of two hurricanes reaching the Central Pacific last year (July 14, 2017). Greg also reached the Central Pacific in July. PC: NOAA/NWS/National Hurricane Center.
NOAA’s Central Pacific Hurricane Center announced on Wednesday, May 23, 2018, that there is an 80% chance of near- or above-normal tropical cyclone activity during the Central Pacific hurricane season this year, June 1 through Nov. 30..
The 2018 outlook indicates equal chances of an above-normal and near-normal season at 40% each, and a 20% chance of a below-normal season.
For the season as a whole, three to six tropical cyclones are predicted for the Central Pacific hurricane basin. This number includes tropical depressions, named storms and hurricanes.
2017 Hurricane track review. NOAA/NWS
Last year, five to eight tropical cyclones were predicted, with two reaching the Central Pacific.
A near-normal season has three to five tropical cyclones, and an above-normal season has six or more tropical cyclones.
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“This outlook reflects the forecast for ENSO neutral conditions, with a possible transition to a weak El Niño during the hurricane season,” said Gerry Bell, Ph.D., NOAA’s lead seasonal hurricane forecaster at the Climate Prediction Center. “Also, ocean temperatures in the main hurricane formation region are expected to remain above-average, and vertical wind shear is predicted to be near- or weaker-than-average. If El Niño develops, the activity could be near the higher end of the predicted range.”
El Niño decreases the vertical wind shear over the tropical central Pacific, which favors more and stronger tropical cyclones. El Niño also favors more westward-tracking storms from the eastern Pacific into the Central Pacific.
This outlook is a general guide to the overall seasonal hurricane activity in the Central Pacific basin, and does not predict whether, or how many, of these systems will affect Hawai‘i.
“It is very important to remember that it only takes one landfalling tropical cyclone to bring major impacts to the State of Hawai‘i,” said Chris Brenchley, director of NOAA’s Central Pacific Hurricane Center. “As we begin this 2018 hurricane season, we advise all residents to make preparations now, by having and practicing an emergency plan and by having 14 days of emergency supplies on hand that will be needed if a hurricane strikes.”
The Central Pacific Hurricane Center continuously monitors weather conditions, employing a network of satellites, land- and ocean-based sensors, and aircraft reconnaissance missions operated by NOAA and its partners. This array of data supplies the information for complex computer modeling and human expertise, which are the basis for the center’s storm track and intensity forecasts that extend out five days.
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October 2017–April 2018 Wet Season Rainfall Summary for Hawai‘i
Started the wet season with drought in every county, including pockets of extreme drought on the Big Island.
Wet season started with weak La Niña conditions for the second consecutive year.
Weak La Niña persisted through the wet season.
Wet season forecast issued in October 2017 called for above average rainfall
over the windward areas. Leeward rainfall depended on La Niña strength.
o Moderate to strong La Nina: dry leeward conditions
o Weak La Nina: wet leeward conditions
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Another erratic wet season, like 2016-17
o October and November: generally wet
o December and January: generally dry
o February through April: very wet
o Record-breaking rainfall produced massive flooding in windward Kauai
Possible U.S. record 24-hour rainfall in Waipa (49.69 inches)
o Drought eased during October and November, then worsened slightly due
to December and January dryness. February rainfall eliminated drought
First time no drought in Hawaii since end of 2015.
Wet Season Statistics
Overall: Fifth wettest wet season in the last 30 years (average rankings from eight
sites)
Big Island
o Most sites 110 to 140% of average.
o Hilo Airport: 101.88 inches, eighth wettest wet season.
Kaua‘i
o Most rain totals in the range of 110 to 140% of average.
o Lihue Airport: 29.47 inches, 13th wettest Oct – Apr in the last 30 years
o Wainiha: 107.58 inches, 2nd wettest Oct – Apr in 30 years, 7th wettest
since 1950. Record was in 1969, 145.98 inches
O‘ahu
o Windward sites mostly 120 to 150% of average.
o Leeward mostly 70 to 100% of average.
o Honolulu Airport: 14.57 inches, ranked 11th wettest.
Maui County
o Many Maui County totals 120 to 150% of average
o Kahului Airport: 21.84 inches, 7th wettest wet season.
Dry Season (May through September) Outlook
La Nina has ended. ENSO-neutral present and is expected to persist through the dry season.
NOAA Climate Prediction Center’s forecast probabilities favor above normal precipitation through the dry season.
Wet conditions will mainly affect the windward slopes across the state and the Kona slopes on the Big Island.
Leeward areas (other than Kona) forecasted to have normal dryness.
o Large areas of severe drought development not expected.
o Abundance of fuels may result in above average leeward wildfire activity.
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