Special Marine Warning 21, NWS Honolulu, HI

538 
FZHW70 PHFO 090552
MWSHFO

Marine Weather Statement
National Weather Service Honolulu HI
752 PM HST Mon Feb 8 2021

PHZ115>118-120-090601-
/O.CAN.PHFO.MA.W.0021.000000T0000Z-210209T0615Z/
752 PM HST Mon Feb 8 2021

...THE SPECIAL MARINE WARNING IS CANCELLED...

The affected areas were... 
Kaiwi Channel...
Maui County Leeward Waters...
Maui County Windward Waters...
Oahu Leeward Waters...
Pailolo Channel...

The thunderstorms associated with the front have weakened, and no 
longer pose a significant threat to boaters.

LAT...LON 2180 15651 2161 15622 2157 15604 2100 15654
      2104 15660 2100 15667 2085 15668 2069 15694
      2045 15758 2059 15774 2063 15819 2072 15844
      2098 15870 2117 15824 2123 15796 2123 15763
      2145 15743 2188 15690
TIME...MOT...LOC 0542Z 306DEG 25KT 2108 15624 2063 15668 2033 15781 

$$

Houston

Area Forecast Discussion
National Weather Service Honolulu HI
404 PM HST Mon Feb 8 2021

.SYNOPSIS...
A fast-moving cold front will sweep down the island chain through
Tuesday, bringing a relatively short period of widespread clouds and
showers, and a chance for thunderstorms. Cool and breezy northerly
winds will strengthen after the front passes, bringing low clouds
and a few showers to northern exposures. Winds will become moderate
trade winds Wednesday through Friday, bringing gradually increasing
windward showers. Southeast winds may bring a further increase in
moisture starting next weekend.

&&

.DISCUSSION...
The leading edge of a cold front is seen on satellite imagery to be
over the Kauai Channel, and rapidly approaching Oahu as it is moving
E near 25 mph. Cloud tops along the relatively narrow (100 mile
wide) cloud line have been cooling through the day, with this deeper
convection likely forming in response to an approaching pocket of
very cold air associated with a mid-level low. As the front moved
over Kauai, wind gusts near 30 mph were reported, with a couple of
thunderstorms and a brief period of very heavy rain. Elsewhere, a
ridge of high pressure is nosing in from the NE over the Big Island
while a surface trough lies to the E and SE of the Big Island.
Moderate to locally breezy S to SW winds have led to some interior
cloudiness on the Big Island, while Maui County and Oahu have been
mostly sunny through the day.

The leading edge of the cold front has been moving faster than
expected, and will reach Oahu shortly, progressing to Maui County
and the Big Island overnight, clearing the Big Island by Tuesday
night. Associated moisture is expected to stall and pool several
hundred miles E of the islands later in the week. The front is
expected to bring a relatively short period of widespread clouds and
showers to most island areas as it passes, with the very cold aloft
dramatically destabilizing the island atmosphere as 500 mb
temperatures drop to -18C. This will bring the chance for
thunderstorms, with a few already noted in the coastal waters around
Kauai today. We can expect wind gusts up to 30 mph or so as the
front passes, mainly from the west, but this frontal passage is not
expected to be impactful as the last. However, we are currently
closely watching a strong thunderstorm in the Kauai Channel.

The cold air aloft will lead to a lowering of the freezing level to
below 10000', bringing the potential for wintry weather on the
Haleakala Summit as well as the Big Island Summits. A Winter Weather
Advisory has been issued, with the potential for fairly short-lived
impacts to occur early Tuesday, possibly lingering into Tuesday
night on the Big Island if moisture is slow to clear.

Cool and breezy north to northeasterly winds will strengthen after
the front passes, driving dew points into the lower 50's (F), and
bringing a renewed chill to the islands. These winds may deliver a
few low clouds and light showers to N facing slopes and coasts. Peak
wind speeds during the day Tuesday may be strong enough to warrant a
Wind Advisory, especially where terrain most accelerates the flow on
Maui and the Big Island, and over Lanai.

A gradually warming and moistening air mass is expected Wednesday
through Saturday, as surface high pressure tracks steadily E along
30N, with the focus for clouds and showers shifting back to the
typical windward areas. As the low aloft exits the area to the E, a
dramatic warming is expected at 500 mb, supporting a very stable
island atmosphere, with limited shower coverage and intensity.
Moderate trade winds are expected to veer to the SE through the
weekend, with some of the pooled frontal moisture sliding back
toward the islands, potentially as early as Friday. Guidance shows
moisture increasing further early next week as another mid-level low
induces a surface trough over the islands, potentially fueling more
widespread showers.

&&

.AVIATION...
A cold front currently located near Kauai will pass over the state
from northwest to southeast. Heavy showers with isolated thunder and
reduced visibility along and ahead of the front have already
impacted Kauai this afternoon. They will continue moving towards
Oahu by around 02Z followed by Molokai and Lanai around 04z and Maui
by around 06Z this evening. The current track of the showers is
progressing faster than model data originally suggested, so improved
flight conditions and clearing can be expected for Kauai this
evening, then for Oahu, Molokai, and Lanai overnight, and eventually
Maui tomorrow morning. Mountain obscurations will be a concern as
the band of low clouds and showers move through the islands. AIRMET
Sierra is posted for tempo mountain obscurations for Kauai and Oahu
this afternoon, and may be issued later this evening over Maui
County. The front is expected to fade near the Big Island during the
day Tuesday.

Post-frontal northeasterly winds will be breezy to locally strong
beginning tonight and spreading west to east. This could create some
low-level turbulence downstream of mountainous terrain. Expecting to
issue AIRMET tango for moderate low level turbulence along the
southern slopes of the islands at 04Z.

&&

.MARINE...
A cold front is currently over the Kauai Channel and is expected to
progress over Oahu and Maui County waters tonight and pass over the
Big Island tomorrow morning, bringing a chance of thunderstorms and
periods showers. Locally strong north winds will fill in behind the
front and shift to northeast trade winds tomorrow afternoon. A small
craft advisory has been issued for all coastal waters as the front
moves down the island chain and elevated seas due to a new northwest
swell.

Forerunners of the next northwest swell are showing up at the
offshore NDBC buoy 51101 in the 20 second energy band with a
dominate swell height of 5 feet period 17 seconds out of the north -
northwest. This new northwest swell will fill in tonight and peak
locally tomorrow afternoon, with surf reaching advisory levels
briefly along most north and west facing shores. A High Surf
Advisory has been issued for exposed north and west facing shores
beginning tomorrow afternoon through tomorrow night. The northwest
swell is expected to drop Wednesday through Thursday. Another, even
larger northwest swell is expected Friday night, with another
reinforcing large northwest swell possible early Sunday. East and
south shore surf will remain small through the forecast period.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from noon Tuesday to 6 AM HST Wednesday for North
and West facing shores of Niihau Kauai Oahu and Molokai and for
North facing shores of Maui.

Winter Weather Advisory until 6 PM HST Tuesday for Haleakala Summit-
Big Island Summits.

Small Craft Advisory until 6 PM HST Tuesday for all Hawaiian waters.

&&

DISCUSSION...Birchard
AVIATION...Vaughn/Foster
MARINE...Almanza