Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 271346 AAA

Area Forecast Discussion...UPDATED
National Weather Service Honolulu HI
346 AM HST Wed Sep 27 2023

Breezy trade winds will continue through the rest of the work
week as high pressure remains far to the northeast of the islands.
Trades will gradually weaken as the high drifts away. An upper
trough developing over the islands will enhance trade showers by
Thursday night near the Big Island before enhancing showers
farther up the chain. Expect increased shower coverage and
intensity across the state by the weekend. Drier and more stable
air will return early next week.


There is little to no change in forecast philosophy from last
evening. A high far northeast of the main Hawaiian Islands is
driving breezy trade winds across local waters this morning.
Overnight soundings showed a stable and rather dry airmass, with
PW from 1.1 to 1.2 inches and positive lifted index values. A
subsidence inversion near 7000 feet kept a cap on cloud
development and limited rainfall amounts. However, the breezy
trades were able to push some showers to some interior and leeward

Models show the high will remain nearly stationary for another
day or so before beginning to move slowly away to the northeast.
Over the weekend, a low far to the northwest will start to push
the trailing ridge southward toward us. This ridge will reach the
islands by next Tuesday. Trade winds will gradually decrease
until becoming light and variable early next week, allowing
development of daytime sea breezes and nighttime land breezes.

Expect a continuation of typical trade wind showers for the next
few days, favoring nights and mornings, across windward and mauka
sections. A shower or two could make it to leeward sections on
the smaller islands. Starting Thursday night, moisture associated
with the remnants of TD14E will begin spreading up the chain.
Upper troughing will move in at about the same time, resulting in
increased shower coverage and intensity Thursday night through
Saturday night. Isolated thunderstorms are possible over waters
west of Kauai and Niihau Saturday night. Models show upper
troughing will weaken and shift north of the islands Sunday and
afterwards. Expect drier and more stable air to return. With
continued light wind flow, also expect a hybrid or convective
shower pattern, featuring localized afternoon interior showers
along with a few across windward and mauka areas.


Breezy easterly trades will continue through the 24-h forecast
period and beyond, with clouds and showers favoring windward and
mountain locations. Some showers will make it to leeward areas,
mainly overnight through the morning hours. Periods with MVFR
CIGs/VSBYs will continue for some windward areas through the
morning hours, especially in passing showers.

AIRMET Tango remains in effect for tempo moderate turbulence
below 9000 feet for areas downwind (south through west) of island
terrain. This AIRMET will likely remain in effect through the next
few days.

AIRMET Sierra for mountain obscuration will likely continue
through the early morning hours before conditions improve.


A high pressure ridge far north of Hawaii will keep fresh to
locally strong trade winds in the forecast through Saturday. The
ridge and wind speeds will weaken on Sunday in response to a
deepening low pressure system northwest of the islands. Wind
directions will shift from a more southeasterly direction from
Monday onward. A Small Craft Advisory (SCA) was extended in time
for windier waters around Maui and the Big Island through Friday.
The SCA may be extended through Saturday for these windier

Surf along south facing shores will continue to slowly decline as
the current small south-southwest swell eases. Mainly background
swells are expected during the second half of the week. Otherwise,
a small southeast swell is possible this weekend into early next

Surf along north facing shores will hold today and slowly decline
tonight through Thursday. A similar size north-northeast swell is
expected to arrive Thursday through Friday, which should keep the
surf from going flat along north facing exposures. For the
extended forecast, guidance is hinting at a slightly larger north-
northwest swell from a low pressure system that is expected to
deepen far northwest of the state later this week. This swell
energy will arrive along exposed north facing shores next week from
Sunday into Tuesday.

Surf along east facing shores will continue to remain rough and
choppy, with a small increase today as the trades strengthen.


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



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