Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Tue Aug 18 2026

Valid 00Z Wed 19 Aug 2026 - 00Z Wed 26 Aug 2026

A trade wind pattern is generally expected over the next several
days, with the typical windward shower activity. A weak wave of
low pressure moving north of the islands by Thursday into Friday
may disrupt the trades and slightly increase instability over the
area. Still looking at scattered shower activity, but may be more
sea breeze and terrain induced compared to the typical windward
trade showers.

NHC is tracking another tropical wave well southeast of the
islands, with a 50% chance of developing into a tropical cyclone
as of early Tuesday. This wave will track westward, with most
model and ensemble solutions continuing to keep it south of the
islands this weekend into early next week. Trends will continue to
be monitored over the coming days, as even a pass to the south
could increase moisture and rainfall across the southern portion
of the island chain. The GFS remains the most aggressive with
this solution, however notably the 00z AIFS and several Google
Deepmind ensemble members track this system close enough to see
an uptick in rainfall potential.

Chenard