Hawaii’s wet season runs from October through April every year.

This year’s outlook calls for a wetter-than-normal start to the season, which could run through the end of the year.

However, forecasters say early 2019 could be drier than normal as a weak El Nino, or warm phase, is expected to form.

There is a 70- to 75-percent chance of El Nino developing during the next couple of months.

“Right now, the consensus of all the climate models are projecting it to be a weak event, so what that means is you can still have some heavy rains come through, although overall, we’re expecting a drier or below average rainfall for the wet season,” explained Kevin Kodama, National Weather Service meteorologist.

El Nino is forecast to persist until the spring when conditions may transition back to an ENSO-neutral state.

Some drought development is expected by the end of February.

Wet Season Rainfall Outlook for the State of Hawaii

Summary of the dry season (May through September 2018)

Statewide: Most locations had above average rainfall. Drought developed in the early summer in Maui County, then spread to the leeward areas of the Big Island and Oahu. Reached severe levels (D2 category in U.S. Drought Monitor map) in small portions of the Big Island and Maui.

Mainly affected ranching operations and contributed to an increase in brush fires.

Tropical cyclone activity and other weather systems produced record-breaking wet conditions in August and September.

2nd wettest dry season in the last 30 years (based on rankings from 8 key sites). 2015 dry season was the wettest in the last 30 years. 2003 dry season was the driest in the last 30 years.

Drought eliminated in early October following vegetation recovery.

Outlook for the wet season (October 2018 through April 2019)

NOAA’s Climate Prediction Center (CPC): The current ENSO-neutral conditions are likely transitioning to an El Niño state (warm phase). There is a 70 to 75 percent chance of El Niño developing during the next couple of months. CPC issued an “El Niño Watch” on June 14, 2018.

After development, El Niño is forecast to persist until the spring when conditions may transition back to an ENSO-neutral state.

Climate model consensus favors a weak strength for this El Niño episode. A weak El Niño usually allows some heavy rain events to affect the state.

Probabilities favor above average rainfall early in the wet season.

Probabilities favor below average rainfall starting December 2018 and persisting into the spring months of 2019. Below average rainfall expected statewide during the winter, but not as dry as 2009-2010.

Some drought development expected by the end of February. Mainly moderate intensity (D1 category), with small areas of severe drought (D2 category) possible along lower leeward slopes. Main impacts to agriculture and homes on rainfall catchment.



Wet season preparedness reminders