High Surf in Hawaii, February 25 to 27, 2022

Area Forecast Discussion...DELAYED
National Weather Service Honolulu HI
340 AM HST Fri Feb 25 2022

.SYNOPSIS...
Moderate to locally breezy trade winds will prevail through
Saturday, before lowering into the light to moderate range on
Sunday. A few showers will affect windward areas, mainly during
nights and mornings, while mainly dry conditions are expected in
leeward areas. Light to moderate trades will hold in place Monday
and Tuesday, but an increase in moisture should bring an uptick in
trade wind showers, as well as a few more showers to leeward
areas each afternoon. A potent upper level disturbance may bring
an increase in rain chances to all or portions of the island chain
during the middle to latter part of next week.

&&

.DISCUSSION...
Currently at the surface, an east to west oriented ridge of high
pressure is positioned around 300 miles north of Kauai, and is
driving moderate to locally breezy trade winds in the non-
sheltered areas across the island chain early this morning.
Infrared satellite imagery shows mostly clear to partly cloudy
conditions, with a bit more cloud cover in some windward locales.
Radar imagery shows a few very light showers moving into windward
slopes and coasts, with dry conditions in leeward areas. Main
short term focus revolves around trade wind trends and rain
chances.

The surface ridge north of the state will move very little
through Saturday, keeping moderate to locally breezy trade winds
in place. A front approaching from the northwest will weaken the
ridge north of the islands by Sunday, with a general light to
moderate trade wind flow holding in place from the tail end of
the weekend through the middle of next week.

As for the remaining weather details, very dry and stable
conditions will hold in place through Sunday, with inversion
heights holding around 5-6 kft and precipitable water values
around 1 inch or less. A few showers will be possible over
windward areas during this time, with mostly dry conditions
expected in leeward locales. Weaker trades may allow for
localized sea breezes and a few afternoon showers in leeward
areas on Sunday however.

Inversion heights will rise and precipitable water values will
climb to more typical levels Monday through Tuesday, which should
bring an increase in trade wind showers. Showers will continue to
favor windward and mauka areas, particularly during nights and
mornings, with a few afternoon showers also developing in leeward
areas. Both the GFS and the ECMWF show a pretty strong upper
level trough moving through the region Wednesday and Thursday,
which could bring an increase in rain chances to all or portions
of the island chain.

&&

.AVIATION...
Breezy easterly trades across the state through tonight, will be
reinforced by a ridge of high pressure north of the islands. Dry
and relatively stable conditions associated with this pattern
will continue to limit the areal coverage and intensity of
showers through tonight, with any showers that do develop confined
again to mainly windward areas through the TAF period. VFR
conditions are expected to continue at most TAF sites, however a
few windward showers may briefly generate MVFR cigs.

AIRMET Tango remains in effect for tempo moderate low level
turbulence downwind of terrain for all islands. With the locally
breezy trade winds expected to persist through Saturday, this
AIRMET is likely to continue throughout the forecast period.

&&

.MARINE...
The high pressure ridge will remain in place north of the Hawaiian
Islands through Saturday producing moderate to locally strong
trade winds. An approaching cold front moving into the Central
Pacific from the west will weaken this ridge and decrease wind
speeds into the light to moderate range from Sunday into the
middle of next week. A hybrid trade wind and near-shore sea
breeze pattern will take hold over the region from Sunday onward.

The large west-northwest swell continues to trend higher at the
Hanalei, Kauai buoy this morning, and the Waimea Bay buoy swell
heights are following this upward trend with both sites reporting
wave periods around 20 seconds. Buoy 1 (51001) northwest of Kauai
at 1:40 AM HST reported 16 foot swell heights with a near 20
second period. These buoy reports are in line with the current
forecast reasoning roughly 2 to 3 feet above GFS Wave model
guidance.

Surf along exposed north and west facing shores will exceed High
Surf Warning (HSW) levels today, then hold through much of
Saturday, before beginning a gradual decline into early next week.
Surf heights into a solid HSW range will peak today and Saturday,
then decline into the High Surf Advisory range on Sunday, and
then drop below advisory levels by Monday morning.

This large west-northwest swell will also bring Small Craft
Advisory (SCA) seas to exposed waters. The SCA includes the
windier waters near Maui County and the Big Island, and all
waters exposed to this swell direction. SCA seas will likely
linger through the weekend with weakening wind speeds on Sunday
and Monday.

There is the chance for overwash from this large swell to impact
the typical vulnerable low-lying coastal roadways. The best chance
of overwash will occur around peak high tide times around
midnight tonight.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 PM HST Saturday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kona-
Kohala-Kauai North-Molokai Windward-Molokai North-Molokai West-
Windward Haleakala.

Small Craft Advisory until 6 PM HST Saturday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Kaiwi Channel-Maui County Windward Waters-
Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.

&&

DISCUSSION...Jelsema
AVIATION...SWR
MARINE...Bohlin