Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
447 AM EDT Wed Oct 7 2026

Valid 00Z Thu 08 Oct 2026 - 00Z Thu 15 Oct 2026

A large extratropical low centered near 30N 160W Thursday morning
will have a trailing front that extends north-south across the
Hawaiian Islands. A small tropical disturbance will emerge from
the ITCZ south of the islands and merge with the front over
Hawaii. This could lead to tropical downpours over nearly all of
the islands Thursday and into Thursday night. A large subtropical
high well northeast of the islands will promote an easterly flow
into the Big Island on Thursday, which in turn will keep the front
stationary. For most of the islands, this means that south to
southwesterly flow will favor heavy rains on the usual lee sides
of the islands. Flash flooding from the rains impacting the
mountains is possible, especially in urban and steep-sloped areas.
For the Big Island and possibly Maui, staying east of the front
will allow for the usual easterly flow into the mountains on those
islands, meaning even those areas may see periods of heavy rain
due to inflow into the front.

By Friday, the front will have largely dissipated in place, but
may begin to drift westward as the aforementioned subtropical high
builds in from the east. For the rest of the period from Friday
night through Wednesday, the high will remain largely stationary,
such that the typical northeast trades dominate the weather
pattern. Above normal amounts of atmospheric moisture with PWATs
between 1.5 and 1.75 inches will still allow for more frequent
showers across the typical windward and mauka areas.

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Wegman