According to NOAA’s Climate Prediction Center, there is an ongoing La Nina event in the Pacific. This La Nina event is expected to persist through the spring of 2021. The consensus of climate models is projecting large scale wetter than average conditions over the Hawai'ian Islands region from December 2020 through April 2021. The distribution of this rainfall may be influenced by the strength of the La Nina. Stronger La Nina events can have a higher than normal trade wind frequency, which will tend to focus rainfall along the east-facing windward slopes. Weaker La Nina events have more weather systems that produce significant leeward rainfall. Early indications are that the current La Nina may reach moderate to strong levels.
La Nina is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator, and the opposite of El Nino, which features warmer-than-average sea surface temperatures in that region.
Senior Service Hydrologist
NOAA – Honolulu Weather Forecast Office
National Weather Service for Honolulu: https://www.weather.gov/hfo/