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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 012000
Area Forecast Discussion
National Weather Service Honolulu HI
1000 AM HST Mon Mar 1 2021
Windy trade winds will persist through Tuesday and lower to
locally breezy speeds during the second half of the week. A more
stable air mass is forecast to build over the islands today as the
upper level trough weakens and drifts south of the Big Island. An
increase of trade wind showers is expected late Thursday into the
weekend as an upper level disturbance moves over the state.
A 1043 mb high far north of the state will produce windy trades
today and a Wind Advisory is in effect across the state. As the
air mass stabilizes this afternoon, winds will likely become more
gusty with wind gusts of up to 50 mph expected. The Wind Advisory
will likely be extended through tonight and potentially through
Tuesday as the winds remain strong and gusty through Tuesday.
Winds are expected to drop down to moderate to locally breezy
speeds during the second half of the week.
As far as precipitation, a drier air mass will begin to move in
today which should decrease rainfall amounts over the next several
days. With the windy trades in place, we will continue to see
passing showers especially during the mornings and nights across
windward areas, but rainfall intensities will generally be light
to moderate. The next notable increase in showers will likely
occur late Thursday through the weekend as moisture from an old
frontal boundary moves in across the state. At the same time, an
upper level trough will move through the state and will bring
unstable conditions across the state. Once again, most of the
shower activity will be focused over windward and mountain areas.
The reduction in upstream cloud and shower coverage noted on regional
satellite imagery is a sign of the drier airmass now filtering
into the area. Ceilings have improved in most areas, although
ceilings in the low VFR range will persist in the near term.
Shower intensity is forecast to diminish this afternoon as mid-
level moisture quality diminishes and convective tops lower,
though locally strong trades will continue to focus showery
weather over windward areas through the forecast period.
AIRMET Sierra for mountain obscuration remains in effect for
Windward Maui and Big Island.
AIRMET Tango for moderate to severe lee turbulence remains in
effect. Tango also remains in effect for locally strong surface
Strong to locally gale force trade winds continue as strong high
pressure holds far north of the state. A Gale Warning is in effect
for the typically windy waters around the Big Island and Maui
County, and a Small Craft Advisory (SCA) remains posted for all
remaining waters due to a combination of winds and large seas. The
surface high will weaken and be replaced by another surface high
far northwest of the islands on Tuesday, starting a short-lived
downward trend in the trade winds. The Gale Warning will be
dropped by Tuesday afternoon, and although winds will be on a
decline, the SCA will likely remain posted for all waters due to
lingering high seas Tuesday night. The SCA may be briefly and
entirely dropped by Wednesday as winds and seas decline to border
line SCA levels. Trade winds should increase again on Thursday and
Friday then hold through the weekend.
Large trade wind-driven seas will maintain high surf along east
facing shores for the next couple of days. Nearshore buoys have
been holding at 10-12 ft at 10-11 seconds since last night, and
these fully developed seas will continue to produce rough east
shore surf well above the 8 foot High Surf Advisory (HSA)
threshold into Tuesday. As trade winds over and upstream of the
islands weaken, east shore surf will decline to border line HSA
levels Wednesday, and the HSA will likely be dropped by Thursday.
Expect east shore surf to be just below HSA levels late this week
and during the weekend.
Surf will remain below advisory levels on other shores through
much of the week. Exposed portions of north and south facing
shores will pull in some wrapping trade wind swell and keep south
shore surf near winter average into Tuesday, followed by a
decline late Tuesday and Wednesday. A northwest swell will arrive
on Wednesday, peak on Friday, then shift out of the north and
decline during the weekend. The bulk of the swell will pass just
east of the islands, though north shore surf may reach HSA levels
Friday and Saturday.
Wind Advisory until 6 PM HST this evening for Kauai-Oahu-Molokai-
Lanai-Kahoolawe-Maui Windward West-Maui Leeward West-Maui
Central Valley-Windward Haleakala-Leeward Haleakala-South Big
Island-Big Island North and East-Kohala.
High Surf Advisory until 6 PM HST Tuesday for Kauai Windward-
Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-South Big Island-Big Island North and East.
Gale Warning until 6 PM HST Tuesday for Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island
Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office