Waimea, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

302
FXHW60 PHFO 200546
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
746 PM HST Wed Aug 19 2026

.SYNOPSIS...

Trade winds weaken Thursday as a surface trough passes over the
islands. The trough also brings an increase in moisture that will
produce an uptick in shower activity through Friday. A new
potential tropical system is forming southeast of the state (90%
chance of formation). Forecasts from the National Hurricane Center
will likely begin Thursday morning.

&&

.SHORT TERM UPDATE...
Forecast looks on track for tonight and Thursday, so no updates are
anticipated this evening. Forecasts from the National Hurricane
center regarding the potential tropical cyclone (EP90) will likely
begin Thursday morning.

&&

.PREV DISCUSSION...
Issued at 533 PM HST Wed Aug 19 2026
We are fully focused on the potential for tropical storm
development to our ESE, and we expect the NHC to begin official
forecasts late tonight or early Thursday morning. At this time,
models suggest it could track similarly to Lala. However, because
a clear center has yet to form, it is impossible to accurately
predict (with any confidence) the details we all want to know.

While we wait for the system to form, we will go ahead and
discuss what we expect over the next couple of days. Trades will
weaken notably Thursday as a surface trough moves over the islands
from east to west. Winds will be weaken enough to allow for a
sea-breeze to develop in some leeward areas, increasing the
chance of showers there. Friday, we`ll see winds slowly increase
in speed and veer to easterly. We`ll see typical trade showers,
mainly over windward and mauka areas, and most common at night,
through Friday night and perhaps into Saturday. Winds and
precipitation over the weekend will be highly dependent on the
track of the tropical system developing to our ESE at this time.

It is likely that precipitation will increase on the east side of
the state Saturday night into Sunday, and then remain high Sunday
night into Monday. On the west side, precipitation will likely
increase Sunday into Sunday night, and last into Monday or Monday
night. Exact timing is impossible to pin down at this time. Wind
speeds will depend on how close it ends up coming to each island.
We urge folks to stay tuned for each new forecast as things will
become clearer and better defined rapidly over time. And as we
noticed with Lala, there will probably be a surprise or two even
after the models seem to have come into agreement.

&&

.AVIATION...
Issued at 533 PM HST Wed Aug 19 2026
Moderate trades expected through tomorrow. Some windward and
mauka SHRA possible with isol MVFR conds, especially into
Thursday.

A tropical Cyclone may impact the region late this weekend.

No AIRMETs are currently in effect.

&&

.MARINE...
Issued at 533 PM HST Wed Aug 19 2026
High pressure to the far northeast will gradually weaken over the
next couple of days. As a trough to the east of the islands
passes on a westward track across the region, moderate trades will
become light and variable for most waters by Thursday, allowing
daytime sea breezes and overnight land breezes to become
established. By late Friday, moderate to locally fresh trades will
begin to build back into the region as the high drifts southward
closer to the island chain and an area being watched closely for
potential tropical development nears the state from the southeast.
The forecast for this weekend will depend on how this next
potential tropical cyclone evolves.

Surf along south facing shores will remain slightly below average
through Thursday, with background swell energy in place. A long
period south-southwest swell generated from gales just south and
east of New Zealand will begin arriving late Thursday into Friday,
boosting surf to near average. Surf along east facing shores will
continue to fade as background flow becomes weaker, then build
heading into this weekend as the trades restrengthen. North
facing shores will remain tiny through Friday, with a slight bump
from Lala swell (290 to 300 degrees) possible this weekend.

&&

.FIRE WEATHER...
Issued at 533 PM HST Wed Aug 19 2026
Trade winds will weaken Thursday, increasing chances of showers
for the leeward side of the islands. Trade winds increase over the
weekend with showers switching to windward. The inversion is 6000
to 7000 ft. The potential for another tropical storm to bring
heavy rain and wind to the state this weekend is becoming high.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...CO
DISCUSSION/FIRE WEATHER...Parker
AVIATION...Munroe
MARINE...Farris