Hanauma Bay State Underwater Park, Hawaii Weather Forecast Discussion

648
FXHW60 PHFO 201302
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
302 AM HST Sat Sep 20 2025
.SYNOPSIS...
Trades will push in moisture from an old front that will move
across the islands today, while a cold pool aloft weakens the
inversion and enhances showers and brings a slight chance of
thunderstorms. Some enhanced showers may continue into Monday due
to troughing aloft with trades focusing along windward areas.
&&
.DISCUSSION...
Satellite and radar shows low clouds and scattered showers moving
over the islands and surrounding waters. These showers are
associated with an old front that will push through today. A
slight chance of a few thunderstorms is possible as the inversion
weakens and enhances showers. Showers are expected to move down
the chain and focus on Maui and Big Island tonight.
Sunday through Monday night another upper level low will track
from the northeast over the islands and continue to enhance the
trade wind showers. Expect wetter weather over windward and mauka
locations.
Drier conditions expected Tuesday into Wednesday as the trades
begin to taper off due to some disturbances moving across the
northeast Pacific.
&&
.AVIATION...
Moderate to breezy trades will persist for the next several days.
Low cigs and SHRA is expected along windward and mauka areas. An
increase in SHRA is also expected across the western end of the
state as a front moves through. An isolated thunderstorm or two
can`t be ruled out for Kauai and Oahu through tonight. Expect
MVFR conds in any SHRA or tstms otherwise VFR prevails.
AIRMET Sierra is in effect for mtn obsc for windward portions of
all islands.
AIRMET Tango is in effect for mod low level turb over and
downwind of island terrain. This AIRMET will likely through the
weekend as breezy trades persist.
&&
.MARINE...
High pressure north of the Hawaiian Islands will keep moderate to
locally strong trade winds in the forecast through at least early
Sunday. A Small Craft Advisory (SCA) remains in effect for the
typically windy waters around the Big Island and Maui through that
time. Trades will gradually weaken Sunday and Monday, and the SCA
will likely be dropped. Trades should remain in the moderate to
locally fresh range through the middle of next week, as developing
low pressure northeast of the islands keeps the local pressure
gradient somewhat weak.
A pair of south-southwest swells are expected during the coming
week. Long period forerunners of the first swell are already
arriving at the southern buoys, and as 16 second energy builds
during the day today, south shore surf should rise to around
seasonal average by this afternoon. This south swell will peak
later tonight, with surf remaining well below the High Surf
Advisory levels. The swell declines early next week, as a smaller
south-southwest swell builds into the region on Tuesday; peaking
on Wednesday.
Small north and northwest swells are due through much of the
week. The current north swell fades today, as a small northwest
swell builds in. This swell peaks later tonight and decline late
Sunday. Recent guidance is depicting a sharp trough developing
several hundred miles northeast of Hawaii on Tuesday and
Wednesday, potentially generating a short period north-northeast
swell that could reach the islands by Thursday.
East facing shores will experience near seasonal average surf
through Sunday due to a mix of trade wind swell and the wrapping
north swell. Surf along east facing shores will gradually decline
Monday through Wednesday, followed by a potential increase on
Thursday.
&&
.FIRE WEATHER...
Humidity levels and wind speeds will remain just below critical
fire weather thresholds this week. A few periods of unsettled
weather will increase humidity levels, clouds and shower chances
through today, with another round from Tuesday into Wednesday.
Temperature inversion heights near the Big Island and Maui today
will range from 9,000 to 10,000 feet.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Walsh
AVIATION...Walsh
MARINE...Bohlin
FIRE WEATHER...Walsh

NWS HFO Office Area Forecast Discussion