Hilo, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

622
FXHW60 PHFO 141348
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
348 AM HST Mon Jul 14 2025

.SYNOPSIS...
A high pressure system will remain locked in place north of the
Hawaiian Islands through next weekend keeping moderate to locally
breezy trade winds into the extended range forecast. Fairly stable
conditions this morning will swiftly change as a disturbance
passes westward through the islands later today, tonight and
tomorrow; briefly increasing shower activity over all islands.
More stable conditions with limited shower activity returns from
late Tuesday through early Friday. Another upper level disturbance
moves over the islands producing a slight increase in shower
activity forecast from Friday afternoon into the weekend.

&&

.DISCUSSION...
A high pressure ridge will remain in place north of the Hawaiian
Islands through the weekend. This means moderate to locally
breezy trade winds for the foreseeable future. The strongest winds
this week will likely develop from Tuesday through Wednesday. The
main weather variable in the forecast will be slight changes to
the cloud cover and shower pattern this week and over the
weekend.

This mornings satellite imagery shows an easterly wave (trough)
swiftly moving westward towards the Big Island. This mornings
upper air balloon soundings from Lihue and Hilo at 2 AM HST (12Z)
show very stable temperature inversion heights hovering around
the 5,500 foot elevation level. This inversion height will lift
rather quickly into the 8,000 to 10,000 foot range as the trough
moves into Maui and the Big Island later this afternoon. Cloud
tops will deepen and shower activity will increase as a result of
increasing instability associated with this trough moving through
each island.

The timing of these increasing shower trends will vary island by
island, the Big Island and Maui will start to see increasing
shower trends later this afternoon, Lanai and Molokai will see
increasing shower trends by this evening, with Oahu and Kauai
picking up enhanced shower trends through the overnight and
Tuesday morning hours. This increase in shower activity will be
brief as a mid level ridge will build in quickly, stabilizing the
atmosphere and decreasing shower trends, as the trough exits the
pattern to the west.

Drier and more stable conditions will return from late Tuesday
into early Friday, as high pressure will keep a subsidence cap on
vertical cloud development. Shower activity will remain isolated
during the day over windward mountains during the day time
periods, becoming isolated to scattered coverage in the overnight
to early morning hours. Any 12 hour overnight rainfall amounts
will likely be on the light side due to the strong stability.

Subtle changes in the island cloud and shower pattern will become
less stable by late Friday into the weekend, as a weak upper
level low injects some instability across the Hawaii Region. A
slight increase in shower trends are anticipated mainly during the
overnight to early morning hours favoring the windward mountain
areas. Confidence in these shower trends are only moderate at this
time as the strength of the upper low is currently projected to
be on the weaker side of the equation. More details will become
clearer later this week, as the time period grows closer, and our
confidence on island by island shower trends improve.

&&

.AVIATION...
A high pressure ridge remains locked in place north of the
Hawaiian Islands this week. Moderate to locally breezy easterly
trade winds remain in the forecast. Shower trends will increase
today and tomorrow as a trough moves westward across the
island chain, starting with the Big Island and Maui later this
afternoon, and then spreading to the smaller islands through
Tuesday morning. Periods of MVFR conditions are expected in any
showers, especially affecting windward airfields.

No AIRMETs are in effect, AIRMET Sierra for Mountain Obscuration
is possible for the eastern islands later today as clouds and
showers increase.

&&

.MARINE...
A ridge of high pressure will remain far north of the state
throughout the week. Moderate to fresh trades will likely continue
through today then strengthen to locally strong speeds from
Tuesday onward as a weak trough exits the region. A Small Craft
Advisory should return to our typically windy waters around Maui
County and the Big Island by Tuesday evening.

Surf along south facing shores should see a modest increase over
the next few days due to a pair of south and south-southeast
swells. A long-period south swell should fill in today and peak
on Tuesday near summer averages. As this swell declines a reinforcing
swell from the south- southeast should fill in Tuesday or
Wednesday. This should maintain surf heights through the middle
of the week. Surf should gradually decline Thursday into Friday,
but another small increase is expected into the weekend as a new
long-period southwest swell arrives from the Tasman Sea.

Surf along east facing shores will continue to remain choppy with
surf heights below average due to the lack of strong trades
locally and upstream of the state. A sight increase is expected
towards the middle of the week as the trades strengthen. A tiny
northwest swell could produce some rideable surf along north
facing shores today into Tuesday.

&&

.FIRE WEATHER...
Trade winds will remain in the moderate to locally breezy range
into the upcoming weekend. Aside from a period of higher humidity
and an increase in shower activity today and Tuesday, the
atmosphere will remain rather dry through Friday.

&&

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

&&

$$

DISCUSSION...Bohlin
AVIATION...Bohlin
MARINE...Walsh
FIRE WEATHER...Bohlin