Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 08/08/2026 04:55:00 PM UTC

                        
482
FXHW60 PHFO 080655
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
855 PM HST Fri Aug 7 2026

.SYNOPSIS...
Breezy trades with light showers this evening. Statewide shower
activity will mainly focus along windward exposures and upslope
mauka with more organized cells passing over ridge tops and
briefly wetting leeward communities. A plume of moisture moving
south of the islands this weekend will likely clip the islands.
This will increase rain chances, especially across Big Island,
from late Saturday through early Monday.

&&

.SHORT TERM UPDATE...
An evening of light to breezy trades as the islands fall between
a 1025 mb high stationed off the U.S. mainland and lower
equatorial pressure. Weak upper troughing just west of the state
will spread mid to high layer clouds across the island chain from
west to east through the overnight hours. Radar is fairly quiet
with the greatest shower activity passing across windward Maui
County and Oahu`s nearshore waters and into the eastern-facing
exposures of those islands. Afternoon soundings depict a very deep
boundary layer, especially over the western islands, that appears
moist enough to support continued pockets of passing easterly
showers, the strongest cells putting down a quick couple of tenths
of an inch upon their quick passage within the trade flow. The
weekend will start off rather dry and warm, but a moisture-rich
easterly air mass in association with a tropical wave or disturbance
passing south of the islands near 10N will increase cloud cover
and initiate more late Saturday through Sunday rainfall. The
highest probability of precipitation is forecast to impact the Big
Island and its surrounding eastern and southern waters early next
week.

&&

.PREV DISCUSSION...
Issued at 309 PM HST Fri Aug 7 2026

High pressure to our north will drive moderate to breezy trade
winds through much of next week. An upper level ridge is currently
moving overhead today along with drier air, allowing showers to
stay light and isolated mostly to windward and mountain areas.
This dry summertime pattern is expected to persist through
tomorrow afternoon with CIMSS MIMIC precipitable water values
estimated at around 1.2-1.3 inches. The 12Z balloon launch from
last night showed precipitable water values around 1.3 inches as
well.

Current satellite imagery depicts a weak tropical low with an
associated tropical wave approximately 560 nm east- southeast of
Hilo. Model guidance projects this low to weaken into a trough as
it moves west- northwest. This trough will have a decent moisture
profile associated with it when it arrives. Current CIMSS MIMIC
precipitable water shows values of around 1.8 to 2 inches
associated with it and it is expected to reach the Big Island by
Saturday evening. Rainfall chances and humidity will increase for
the Big Island and Maui County, then to a lesser extend, Oahu and
Kauai Sunday into Monday. The most recent GFS model time- height
cross section depicts the boundary layer inversion weakening, as
conditions become more unstable, and moisture deepening up to at
least 15,000 feet. Thus, from Saturday afternoon through Monday,
embedded heavy rainfall will be possible for the Big Island and
Maui County, especially for windward locations.

Though it is still too early to fine tune the forecast storm
total amounts, typically wetter windward locations on Maui and the
Big Island could pick up a couple inches of rainfall
accumulation. Sufficient instability may exist for a rumble of
thunder Sunday afternoon over the south or southwest slopes of
Mauna Loa on the Big Island, but confidence is too low at this
time to add to the current forecast package.

Typical summertime stable trade wind weather will return Tuesday
through the end of the week with scattered showers mainly windward
and mauka areas during the nights and early mornings.

Looking into the long range forecast for late next week, both
Google Deepmind and global dynamic models are showing potential
tropical cyclone development in the central Pacific. Details are
far too early at this time but warrants further monitoring.

&&

.AVIATION...

Moderate trades to slightly increase through tomorrow. Low cigs
and SHRA likely over windward and mauka locations. MVFR conds
possible otherwise VFR prevails.

No AIRMETs currently in effect, however AIRMET Tango may be needed
for mod turb downwind of terrain as winds increase.


&&

.MARINE...
Issued at 309 PM HST Fri Aug 7 2026

Moderate trades will continue to strengthen to fresh to locally
strong speeds by this evening as surface troughing to the
northeast weakens and a trough approaching from the southeast
enhances the local pressure gradient. A Small Craft Advisory is in
effect for locally strong trades across the typical windy
channels and waters around Maui County and the Big Island. Fresh
to locally strong trades will persist through at least the
weekend, with the strongest winds over the southern portion of
Hawaiian coastal waters as the surface trough nears.

Background medium- and long-period energy will continue to
produce small surf along south-facing shores through tonight. A
series of larger, medium- to long-period south swells will cause
surf to trend upward along south- and west-facing shores from this
weekend into early next week. A moderate, long-period south swell
will peak near High Surf Advisory thresholds by midweek.

Along east-facing shores, trade wind swell will remain slightly
below seasonal averages today before building this weekend in
response to strengthening trades. Surf along north-facing shores
will remain flat to tiny through the period, though a small,
medium-period north swell could bring a slight bump on Sunday.

Due to a combination of peak monthly high tides and water levels
running higher than predicted, minor coastal flooding is possible
around the daily peak tide during the afternoon hours late this
weekend into early next week along vulnerable shoreline areas.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Saturday for Alenuihaha
Channel-Big Island Leeward Waters-Big Island Southeast Waters-
Maalaea Bay-Pailolo Channel.


&&

$$

UPDATE...Blood
PREV DISCUSSION...Tsamous
AVIATION...Walsh
MARINE...Farris