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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 280145
Area Forecast Discussion
National Weather Service Honolulu HI
345 PM HST Wed Jan 27 2021
A trade wind weather pattern is expected over the next several
days thanks to high pressure north of the area. Clouds and passing
showers will favor windward and mauka areas with the trade winds
sufficiently strong enough to blow a few brief showers over
leeward areas at times. Winds will become southerly early next
week as a front approaches from the northwest. The front is
expected to move into the western and central islands Tuesday
night and Wednesday accompanied by a period of showers.
A 1030 mb surface high is centered far to the north of the state.
This is providing for breezy trade winds across the area.
Moisture embedded in the trades is providing for some passing
showers for windward and mauka areas with most leeward locations
remaining dry. The exception is the Kona slopes on the Big Island
where daytime heating has caused clouds and showers to form.
Expect this weather pattern to persist through Thursday.
On Friday, moisture associated with an old front will get caught
up in the trades and will likely provide an uptick in shower
activity especially for windward and mauka locations. The trade
winds will be sufficiently strong enough to blow some brief
showers over to select leeward locations at time. This area of
moisture should be through the state by Saturday. The high will
linger north of the area on into early next week. Passing showers
will continue to favor windward and mauka areas and be highly
dependent on incoming moisture availability.
Long range guidance indicates a front will be approaching the area
from the northwest Monday and Tuesday. Winds will become lighter
and trend around to a southerly direction. There may be some
increase in showers out ahead of the front especially on Tuesday.
Current timing has the front reaching Kauai Tuesday night and
then moving across Oahu and Maui County on Wednesday. The front
will be accompanied by a period of showers, some could be locally
heavy. It's still a bit far out in the forecast to add in the
potential for thunderstorms but current guidance does indicate
that there is some potential. Later shifts will be able to get a
better handle on the situation as the event becomes closer in
time. Cooler northerly flow will fill in behind the front.
Breezy trade winds will carry in clouds and showers into tonight
bringing tempo MVFR/isolated IFR conditions along windward slopes.
AIRMET Sierra is in effect for tempo mountain obscuration is in
effect for windward sides of Big Island, Maui, Molokai, Oahu and
Kauai. Fewer clouds and showers are expected by Thursday.
AIRMET Tango remains in effect for low-level mechanical turbulence
leeward of all islands due to strong low level winds.
A strong high pressure system far north of the state will keep
fresh to locally strong easterly trade winds in place through
Friday. A slight decrease in trade winds into the moderate to
breezy range will develop by this weekend, as a weaker high
passes by far north of the island chain.
Large surf along east facing shores will continue through Friday
morning. The easterly trade wind swell will gradually decrease
from Friday afternoon through the weekend as the high pressure
system north of the area weakens. A Small Craft Advisory (SCA) for
all Hawaiian waters is in effect through early Friday morning. A
High Surf Advisory (HSA) for exposed east facing shores is in
effect through tomorrow afternoon. This HSA may extend into
Friday due to continued strong trade winds.
The current small northwest swell will continue to hold through
tomorrow with a slight reinforcing bump Thursday night. A new
moderate, long- period northwest swell will spread across the area
late Friday, and continue through Saturday night. Northwest swell
heights will slowly lower from Sunday into early next week.
Forerunners of a small, long- period north- northeast swell will
arrive tomorrow and will likely continue through the weekend.
The current small out-of-season southwest swell from the Tasman
Sea will slowly drop tonight. Otherwise, expect small background
south swells through the weekend into early next week.
High Surf Advisory until 6 PM HST Thursday for Kauai Windward-
Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-Big Island North and East.
Small Craft Advisory until 6 AM HST Friday for all Hawaiian
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office