Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Sun Aug 9 2026

Valid 00Z Mon 10 Aug 2026 - 00Z Mon 17 Aug 2026

...Heavy rain/increasing wind threat from Friday onward...

The general flow pattern features an upper level trough 
retrograding away through the Papahanaumokuakea Marine National 
Monument mid-week and a warm core ridge strengthening/broadening 
to the northeast of Hawai'i. Trade winds continue through at 
least Thursday.

An easterly wave/low-level swirl to the south-southeast of the Big
Island increases moisture through Sunday/possibly into Monday 
which increases heavy rain potential primarily on the island of 
Hawai'i. Mauka showers are expected thereafter through at least 
Thursday. 

A developing/strengthening tropical cyclone is forecast to move 
near Hawai'i as early as Friday or Saturday, bringing an 
associated heavy rain threat. Unlike the guidance from 24 hours 
ago, it's no longer clear which side of the archipelago it would 
track (south, very close, or north) leaving the wind direction 
forecast unclear. Winds could very well increase across some of 
the main islands with this system late in the week/next weekend. 
See National Hurricane Center Tropical Weather Outlooks for more 
on this impending system.

Roth