Maunakea Weather Center

NWS Bulletins for NPAC - MKWC

Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans:
Narrow the Menu List
Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit
Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special

Hawaiian Islands Synoptic Discussion and Guidance

024
FXHW60 PHFO 291348
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
348 AM HST Fri Mar 29 2024

.SYNOPSIS...

Windy easterly trade winds will gradually ease today into the weekend
as a strong high pressure slowly drifts northeast and weakens. Showers
will favor windward and mountain areas with some reaching the leeward
areas. Drier and more stable conditions will return over the weekend,
while the easterly trades become gentle to locally breezy. Rainfall
chances could trend up again early next week as a disturbance moves
through.

&&

.DISCUSSION...

The strong high north of the state has begun to gradually weaken
and is slowly moving further northeast of the state. This has
translated to winds easing slightly overnight based on recent
observations. Breezy to locally windy winds are expected to
continue to ease throughout the day today thus the Wind Advisory
for the typically windier areas of Maui County and the Big Island
has been cancelled. A band of clouds and showers is currently
moving through Maui County and the Big Island. Showers will trend
down this afternoon as an area of clear skies and isolated showers
moves in. Chances of clouds and showers will pick up again
tonight as another shallow band of moisture moves through. These
showers will be moving through swiftly with minimal accumulations
anticipated.

Drier and more stable conditions will briefly return over the weekend
as upper heights rise and precipitable water dip to around an inch.
Trade winds are expected to ease to a more gentle to locally
breezy range by Sunday as the high weakens far northeast of the
state and a front approaches the state from the far northwest.

Latest guidance from both the ECMWF and the GFS are now placing a
surface trough between the state and very strong developing high
(1050 mb) to the far north early next week. This setup may produce
a weaker wind pattern than previously forecast and allow hybrid
land/sea breeze pattern to develop over the western half of the
state while trades veer out of the southeast over the eastern half
of the state. Models continue to show an upper level trough
digging southward over the region. These features may allow for
precipitable water to gradually increase and provide enough
instability to allow for an increased chance of heavier showers
particularly along windward areas and perhaps interior areas each
afternoon.

A return of breezy to strong trades is possible during the second
half of next week as a low develops along the northern end of the
trough and moves northwest of the area allowing a surface ridge to
build in from the east. A more typical tradewind pattern may then
return.

&&

.AVIATION...

Surface high pressure north of the state will maintain strong and
gusty winds today, though winds are expected to be slightly
weaker as compared to yesterday. Winds will continue to trend
lighter through the weekend as the surface high moves off to the
northeast. Low level moisture carried in on the trades will bring
clouds and showers to windward and mauka areas, with the best
chance of seeing periods of MVFR conditions during the overnight
to mid morning hours when shower activity will be at its peak.
Otherwise, VFR conditions will prevail.

AIRMET Sierra for tempo mountain obscuration is in effect for
windward portions of the smaller islands. Ceilings and
visibilities should improve by the afternoon.

AIRMET Tango remains in effect for tempo moderate turbulence lee
of the island terrain. This AIRMET will likely be needed through
this evening. AIRMET Tango is also in effect for 30 kt or greater
winds from Molokai to the Big Island and will likely be dropped
later today.


&&

.MARINE...
Fresh to strong easterly trades will continue through Saturday,
then ease into the moderate to fresh range Sunday through Monday
as the surface ridge weakens north of the state. This will
support transitioning the gales in place over the Pailolo and
Alenuihaha Channels back to a Small Craft Advisory (SCA) today,
and reducing the coverage of the SCA to the typically windier
zones from Oahu to the Big Island today through Saturday. For the
extended forecast (Tuesday through midweek), confidence remains
low due to model discrepancies and inconsistent solutions from
cycle to cycle over the past few days. Although we would typically
anticipate strong- to gale-force easterly trades with the ~1050
mb high setting up north of the state, the positioning of the
tail-end of the aforementioned front between this high pressure
system and the Hawaiian waters is making this challenging to
predict at this time.

Surf along exposed north and west facing shores will remain small
through early next week, with mainly overlapping small northwest
medium- to long-period swells moving through. An upward trend is
possible beginning Tuesday as a potential moderate sized, short-
to medium-period north swell arrives from a decent sized area of
north to northeast winds focused at the islands nearby to the
north between the strong high pressure system and tail-end of the
front. Again, confidence in the details for this setup remains low
at this time.

Surf along east facing shores will remain rough and choppy due to
the strong winds impacting the area locally and upstream. As the
winds lower over the weekend, expect the surf to ease and remain
small into Monday. Similar to north facing shores, an upward trend
is possible by midweek depending on how the scenario evolves,
particularly for shores exposed to north to northeast swells.

Surf along south facing shores will remain small with mainly a
combination of background south-southwest swells and shorter
period southeast trade wind energy moving through. For the
extended (late next week/weekend), a small medium-period southeast
swell can't be ruled out. Guidance continues to show a decent
sized batch of strong southeast winds setting up southeast of the
Tuamotu Islands late this weekend into early next week that is
focused at the islands within the 150 deg directional band.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST this evening for Oahu
Leeward Waters-Kaiwi Channel-Maui County Windward Waters.

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


&&

$$


DISCUSSION...Almanza
AVIATION...Farris
MARINE...Gibbs

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office