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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 252002
Area Forecast Discussion
National Weather Service Honolulu HI
1002 AM HST Sun Oct 25 2020
A surface ridge over the islands will produce locally breezy
southeast winds around the Big Island and light and variable
winds around the smaller islands through tomorrow. Sea breezes
will produce clouds and spotty showers over interior sections of
all islands during the afternoon hours while land breezes will
bring clearing skies at night. A strong low aloft is forecast to
form northwest of the area tomorrow. The atmosphere over the
islands will become very moist and unstable. This combination
will likely produce cloudy, wet weather starting as early as
tomorrow night. Wet weather may continue through the week.
As of 9 AM, quiet weather prevails over the main Hawaiian
Islands. Locally breezy southeast winds are producing clouds and
isolated showers over southeast sections of the Big Island and
Maui. Gentle variable winds and mostly sunny skies prevail
A surface ridge extending northeast from near the islands is
producing the southeast flow near the Big Island. The Big Island
partly blocks the southeast flow so winds are gentle and variable
around the smaller islands. The southeast flow will continue to
push clouds and isolated showers over the Big Island and Maui
through tomorrow. Elsewhere, clouds and spotty showers will form
over interior areas during the afternoon today and Monday while
land breezes will bring clearing clouds tonight.
The global models show a deep low aloft forming northwest of the
main Hawaiian Islands by tonight, then dropping south. That will
make the atmosphere unstable and pull moist tropical air over
islands. The GFS and ECMWF have been inconsistent with each other
and have been much different from model run to model run. At this
time, the best chances for enhanced showers, and possibly
thunderstorms, appear to be over Kauai and Oahu but there could be
heavy rain state-wide. Because of the model differences, confidence
is low for the the duration of the heavy rain.
Radar imagery shows little in the way of showers across the state
this morning. The few that exist are focused around Kauai with the
lingering moisture axis and windward areas of Maui and the Big
Island on the southeast flow. These overall conditions are expected
to continue through the day with prevailing VFR for all locations.
Sea breeze development is anticipated again for most leeward areas
this afternoon, which will favor some inland cloud build-ups and
a few showers through early evening. These areas will once again
clear out overnight with the land breeze.
No AIRMETs are in effect, nor expected through tonight.
High pressure will remain far to our northeast over the next
several days with its associated ridge axis extending southwest to
a position just north of the state. Southeast flow prevails
across the area with the strongest winds east of Maui and the Big
Island. A front will be approaching the area from the west
Tuesday through Thursday with unsettled weather a possibility.
A High Surf Advisory is currently posted for most north and west
facing shores from Maui county westward as a moderate size long
period northwest swell moves through the Hawaiian coastal waters.
The swell is running a couple of feet higher than model guidance.
The height of swell is expected to remain about the same through
Monday but the periods will gradually become lower with time. This
swell will lower gradually Monday night through Wednesday.
Another moderate size long period northwest swell may arrive late
A small, medium period northeast swell is expected to fill in
later today, then linger on through Tuesday. There will also be a
series of small long period south swells through most of this
High Surf Advisory until 6 AM Monday for north and west facing
shores of Niihau, Kauai, Oahu, and Molokai and for north facing
shores of Maui.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
This page is maintained voluntarily by the MKWC and the UHMET faculty, staff, and students.
It was last modified on: Wed, Dec 17 2014 - 1841 UTC
Send comments to: Ryan Lyman