Special Marine Warning 13, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
958 AM HST Wed Feb 3 2021

.SYNOPSIS...
The cold front has moved through Kauai and is now moving through
Oahu. This front is expected to move through Maui County this
afternoon and the Big Island this evening. Windy conditions are
being reported ahead and along the front with wind gusts of 50 mph
seen at select locations. In addition, thunderstorms are producing
locally heavy rainfall along the front. The threat of heavy rain
will end behind the front as the cool and breezy northwest winds
fill in. Cool conditions with some light passing showers are
expected Thursday through the weekend.

&&

.DISCUSSION...
A strong cold front has made its way through Kauai and the cool
northwest winds has filled in behind it. Light to moderate showers
are still expected through the rest of the day today, but the
threat for heavy rain and thunderstorms has ended for Kauai. The
winds over Kauai has subsided for a brief moment, but windy
northwest winds are expected to fill in this afternoon and
continue through the evening. Temperatures are expected to drop
down into the mid to upper 50s for many areas on Kauai tonight.

The front is now moving through Oahu and radar is estimating
widespread rainfall rates of 1 to 2 inches per hour with pockets
of locally higher rates along the front. Gusty winds have been
reported with the front with wind gusts of over 50 mph seen at
select areas. As the front makes its way through Oahu over the
next few hours, we should see improving weather conditions later
this afternoon with cool northwest winds filling in behind the
front. A period of lighter winds are expected this afternoon, but
breezy northwest winds are expected to fill in this evening for
Oahu.

The front is expected slowly weaken and move through Maui County
this afternoon and the Big Island this evening. The main impacts
will likely be gusty winds ahead and along the front with wind
gusts of 50 mph expected. Winds this strong will be capable of
causing power outages. Winds have already picked up over Maui
County and they should see winds continuing to increase during the
afternoon. The strongest wind gusts are expected on the lee side
of the terrain. In this case, that will be the north and east
sections of the islands. Also on the summits of the Big Island,
they should see a period of moderate to locally heavy snow as the
front pushes through.

By Thursday the front should be east of the Big Island and we
should see cool conditions with a few light passing showers.
Overall, we should see mostly dry and cool conditions through the
weekend.

&&

.AVIATION...
Prefrontal showers containing MVFR/locally IFR conditions and
gusty southerly winds are spreading across Oahu and will reach
Molokai by midday, Maui shortly thereafter. Shower coverage and
intensity will trend downward as the front weakens while
traversing Maui County. Another round of brief, lower intensity
showers can be expected along the cold front itself as it lags the
primary rain band by a couple of hours. Veering winds to the
northwest will mark the beginning of improving conditions to
prevailing VFR this afternoon through tonight. In the meantime,
AIRMET Sierra for mountain obscuration remains in effect for Kauai
through Molokai. Further expansion to Maui may be needed during
the afternoon.

&&

.MARINE...
A strong cold front will move southeastward across the island
chain through tonight and be east of the Big Island by daybreak
Thursday. Fresh to strong south southwest winds are expected in
advance of the front with strong northwest winds in the wake of
its passage. Post-frontal moderate becoming gentle slowly veering
northerly winds will occur from Thursday through Friday night. The
slow eastern progression of the upper low will somewhat anchor
the surface low north of the islands through the weekend. Thus,
this will keep west winds in place north of the state while
southern water northeasterly winds veer back to trade wind flow
Sunday. Monday's winds will return to weak trades ahead of the
next cold front. This front is timed to travel across the islands
next Tuesday and turn winds northerly through the day.

Strong wind gusts in association with the front has a Small Craft
Advisory (SCA) is in effect for most waters (except for the Big
Island southeast waters) through 6 PM this evening. The SCA will
certainly need to be extended in time for high seas to account
for the arrival of the large northwest swell through Thursday.

There are signs in the swell spectral data from the far northwest
island buoys that the front runners to this upcoming high northwest
swell are arriving this morning. The northwest swell will build
down over the chain today and tonight, peak surf Thursday then
gradually subside from Thursday night into the weekend. Surf is
expected to reach and exceed high surf warning levels along the
north and west-facing shores of Kauai overnight Thursday morning,
with low-end warning level surf expected to reach Oahu's northern
and western exposed shorelines, Molokai and Maui's north-facing
shores Thursday. Surf will remain elevated through at least Friday
night before dropping below advisory levels on Saturday. Surf
will remain below advisory thresholds through the middle of next
week.

The more westerly component of this swell will likely introduce
advisory level surf to the west-facing shores of the Big Island
Thursday. Surf may even reach warning levels later that afternoon
into the early Friday morning hours.

Stronger south southwest winds ahead of the approaching cold
front will provide a slight boost in short period, wind-driven
surf along south-facing shorelines.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM HST this evening for Niihau-Kauai-Oahu-
Molokai-Lanai-Kahoolawe-Maui-Kona-South Big Island-Big Island
North and East-Kohala-Big Island Interior.

Winter Weather Advisory from noon today to 6 AM HST Thursday for
Big Island Summits.

Small Craft Advisory until 6 PM HST this evening for Maui County
Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-
Big Island Windward Waters-Big Island Leeward Waters.

Small Craft Advisory until 6 AM HST Thursday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters.

&&

DISCUSSION...Kino
AVIATION...JVC
MARINE...Blood

Special Weather Statement
National Weather Service Honolulu HI
758 AM HST Wed Feb 3 2021

HIZ005>011-031900-
Oahu Koolau-Oahu North Shore-Waianae Coast-Oahu South Shore-Waianae
Mountains-Olomana-Central Oahu-
758 AM HST Wed Feb 3 2021

...GUSTY WINDS AND HEAVY RAIN TO IMPACT OAHU THIS MORNING...

At 755 AM HST, radar indicated a line of heavy showers, with a few
embedded strong thunderstorms, approaching Oahu from the west. This
line will move east at 20 to 25 mph, and will impact Oahu through
most of the morning. Southwest to west winds will gust near 50 mph,
and visibility will be severely reduced as these showers and storms
move across the island.

Locations impacted include...
All of Oahu, but the strongest wind gusts can be expected in
windward Oahu from Waimanalo to Kaneohe, over central Oahu near
Wahiawa, and on the north shore near Mokuleia and Waialua.

Torrential rainfall is also occurring with these storms, and may
cause localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 2151 15784 2147 15784 2141 15778 2145 15773
      2141 15774 2131 15766 2126 15770 2130 15772
      2128 15775 2134 15790 2130 15811 2151 15824
      2153 15823 2158 15827 2158 15812 2171 15797
TIME...MOT...LOC 1727Z 261DEG 28KT 2249 15814 2107 15893

Birchard