Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
340 AM EDT Mon Oct 19 2026

Valid 00Z Tue 20 Oct 2026 - 00Z Tue 27 Oct 2026

Hawaii and the adjacent waters will be to the south of a
subtropical high that will be situated near 35 degrees north for
the beginning of this week, with steady ENE trade winds expected
through Wednesday. A well defined col develops within this
subtropical high by Wednesday night as a developing low pressure
system over the North Pacific heads towards the ESE and brings a
frontal boundary closer to the northwestern Islands, and therefore
weaker and more variable winds.

The guidance also starts to diverge on how this system evolves
north of the state towards the end of the week. The GEFS mean
becomes more progressive and stronger, and has the low well to
the northeast of the ECENS mean. Going into the weekend, the ECENS
favors more of an inverted surface trough, whereas the GEFS
maintains a closed low northeast of the Islands. The deepest
tropical moisture should stay confined well to the south, but some
higher PWs and increased rainfall chances arrive by Friday and
into Saturday as the trough advects some of this moisture towards
the north.

Hamrick