Keauhou, Hawaii Weather Forecast Discussion

481
FXHW60 PHFO 200140
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
340 PM HST Fri Sep 19 2025
.SYNOPSIS...
Trade winds will push in moisture from an old front that will
move across the islands through Saturday, 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...
Visible satellite and radar shows an area of low clouds and
showers over windward areas and waters. These showers are
associated with an old front with breezy trades driven by the
subtropical high. Cold air aloft is creating somewhat unstable
conditions in the atmosphere over the western islands, which is
enhancing the incoming showers. 00Z sounding at Lihue nearly 1000
J/kg mixed layer CAPE and decent precipitable water of 1.64
inches.
Trade winds will push in moisture from the old front through
Saturday, while a cold pool aloft weakens the inversion and
enhances showers and brings a slight chance of thunderstorms.
Showers are expected to fill in a bit more overnight tonight and
then shift focus on Maui and Big Island on Saturday and Saturday
night. Sunday into Monday night a new upper low will track from
the northeast over the islands and continue to enhance the trade
wind showers from below. So expect a the wetter weather to
continue especially for all windward areas.
Drier conditions expected Tuesday into Wednesday as the trades
begin to taper off due to some disturbances moving across the
northeast Pacific.
&&
.AVIATION...
The remnants of an old front are moving towards the island chain
this afternoon on moderate to breezy easterly trade winds. As this
feature approaches, an increase in clouds and showers along mainly
windward and mountain locations is expected. The best chance for
increased shower coverage and prevailing MVFR ceilings and
visibilities will be tonight through early Saturday, especially
for the western end of the state. An isolated thunderstorm or two
can also not be ruled out for Kauai and Oahu through tonight.
Meanwhile, moderate to breezy trade winds will continue for the
next several days. AIRMET Tango remains in effect for moderate
low level turbulence over and downwind of island terrain. This
AIRMET will likely through the weekend as breezy trades persist.
&&
.MARINE...
High pressure far north of the state will maintain moderate to
locally strong trade winds through at least early Sunday, and a
Small Craft Advisory (SCA) is 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 will arrive
tonight, and as 16 second energy builds during the day on
Saturday, south shore surf should rise to around seasonal average
by afternoon. The swell will peak Saturday night and Sunday, with
surf remaining well below the High Surf Advisory level. As this
swell declines early next week, a smaller south-southwest swell is
expected to build on Tuesday and peak on Wednesday.
Small north and northwest swells are due through much of the
week. As the current north swell fades on Saturday, a small
northwest swell will build in. This swell will peak Saturday night
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. Even as local trade winds start to ease on Sunday,
east shore surf should hold due to a narrow fetch of short period
wind swell aimed at the islands. Surf along east facing shores
will gradually decline Monday through Wednesday, followed by a
potential increase on Thursday from the above mentioned source
from the north-northeast.
&&
.FIRE WEATHER...
Humidity levels and wind speeds will remain just below critical
fire weather thresholds this week. A few periods of unsettled
weather conditions will increase humidity levels, clouds and
shower chances starting later this afternoon through Saturday,
with another round from Tuesday morning into Wednesday. Temperature
inversion heights near the Big Island and Maui today will range
from 7,000 to 8,000 feet elevation.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Foster
AVIATION...Vaughan
MARINE...Wroe
FIRE WEATHER...Foster

NWS hfo Office Area Forecast Discussion