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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 191957

Area Forecast Discussion
National Weather Service Honolulu HI
957 AM HST Sat Sep 19 2020

The stable trade wind pattern will continue into next week, with
the best chance for showers developing overnight through the early
morning periods across windward and mountain locations. Moderate
to locally breezy trade winds will continue through next week, but
may weaken just a touch on Monday and Tuesday, before picking
back up towards the middle of next week.


A ridge of high pressure far north of the state will maintain
breezy trade wind weather through the weekend. Latest satellite
imagery is showing mostly dry conditions this morning, but a few
light showers are making its way over the windward and mauka
areas of Oahu this morning. Looking upstream of the state, we do
have some patches of cumulus clouds headed toward Oahu and Maui
County this afternoon which may bring some light showers.

For tonight we are expecting a slight uptick in moisture, which
should produce some showers over windward and mauka areas through
Sunday morning. Showers should be on the decrease Sunday
afternoon with a return back to mostly dry trade wind weather
expected for the upcoming week. Passing showers should favor the
overnight and early morning hours across windward and mauka
locations. The current breezy trade winds should drop a touch on
Monday and Tuesday and pick back up towards the middle of next


A high far north of the area will maintain moderate to locally
strong east winds over the area. VFR conditions will prevail, but
the low level flow will push some clouds and showers over east
sections, mainly during the night and early morning hours.
Sea breezes will bring some clouds and showers to the southwest
section of the Big Island of Hawaii during the afternoon and
evening. A trough aloft just west of the main Hawaiian Islands
will keep high, cirrus, clouds over the area.

No AIRMETS are in effect.


High pressure is expected to remain north of the islands into next
week, maintaining a trade wind flow. ASCAT passes last night
showed moderate to locally fresh trades, with the highest winds as
expected in/near the typically windier locations near Maui County
and the Big Island. The Small Craft Advisory (SCA) for these areas
has been posted through Sunday afternoon. The high to the north is
expected to weaken next week as a front passes by north of 30N.
This will in turn weaken the winds some over the islands. A new
high is expected to build in behind that front, which could boost
winds later in the week.

A long period southwesterly swell will bring surf just below
advisory levels today and tomorrow. This swell will begin to
subside some Sunday night and Monday, with long period energy
persisting through the new week. Meanwhile a northwest swell
arriving today will bring a boost to the north and west shores,
before declining some early in the week. A longer period north
swell is expected mid week. The moderate to locally fresh trades
will boost surf along east facing shores.


Provided the lack of any significant rainfall through the summer
months, fuels remain very dry across portions of the state.
Although the KBDI and relative humidity values will likely reach
criteria this afternoon, the trades should remain near/just below
red flag criteria.


Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.



MARINE...M Ballard

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office

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It was last modified on: Wed, Dec 17 2014 - 1841 UTC
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