High Surf in Hawaii, February 1 to 2, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Thu Jan 31 2019

.SYNOPSIS...
Strong and gusty north-northeast winds will persist at least through
this evening due to a surface trough east of the Big Island and a
surface high to the far north. Low clouds and showers carried by the
winds will reach the state at times. The winds will weaken slightly
and become more easterly starting Friday as the trough moves east.
Wind speeds will decrease a little more over the weekend.

&&

.DISCUSSION...
Due to the present of a surface trough east of the Big Island and a
surface high far north of the state, rather tight pressure gradient
across the area continues to support strong and gusty
north-northeast winds over most of the state this evening. A Wind
Advisory remains in effect for most of the western islands and parts
of Maui and the Big Island through this evening and may need to be
extended if the strong winds persist. The strongest winds will still
likely be over mountain ridges and through valleys on the south and
southwest sides of the islands. Latest satellite imagery revealed
quite a bit of low clouds in the island vicinity. The strong
northerly winds will carry these clouds across the area, favoring
north and northeast facing sections. Winds are strong enough for
these clouds and showers to reach the lee areas of the smaller
islands. There will be measurable rainfall amounts from these
passing showers, though the swift movement of these showers will
lessen the flood threat for the area.

Still expect the winds to ease a little on Friday as the surface
trough shifts east. Moreover, winds will turn more easterly, as a
surface high pressure continues far north of the area. Forecast
solutions still indicated much moisture will be lingering in the
island vicinity. Furthermore, An upper trough is forecast to pass
the islands over the weekend. Airmass in the island vicinity may
become unstable enough for the thunderstorms to develop on Saturday.
But then, forecast solutions also have this trough passing the
islands rather quickly, thus limiting the duration of the favorable
atmospheric conditions for thunderstorm development. Shall keep the
mention of thunderstorms out of this forecast package for now, but
shall revisit this issue after checking out the newer forecast runs.
Regardless, wet trade wind weather with enhanced showers is in store
for the islands Saturday and Sunday.

A surface high pressure is expected to persists far north of the
region next week, with indicate bands of moisture affecting the
islands at times according the models. Hence, the islands see the
somewhat wet trade wind weather to continue.

&&

.AVIATION...
A high pressure system far to the north of the islands will produce
breezy to locally windy trade winds tonight with bands of showers
northeast of the state moving in with the trade winds. Expect
periods of showers and MVFR ceilings as these bands reach the
islands through the overnight hours. Winds will remain strong enough
for moderate low level mechanical turbulence over and south through
west of all mountains. Moderate to isolated severe turbulence was
reported over Lanai Airport this evening. Wind speeds should
decrease by Friday morning statewide.

AIRMET Sierra remains in effect for mountain obscuration Oahu,
Molokai, Lanai, and Maui above 2000 ft due to low cloud ceilings.

AIRMET Tango remains in effect through at least the next 12 hours
over and immediately south thru west of mountains for tempo moderate
turbulence below 9000 feet. An additional AIRMET was issued this
evening for moderate to isolated severe turbulence below 9000 feet
over Lanai. Surface winds 30 KTS or greater are forecast over the
mountains and through valleys. Winds will ease slightly by early
Friday morning.

&&

.MARINE...
High pressure will hold in place to the north of the islands through
the weekend. Moderate to strong northeast winds will continue
tonight as the gradient remains tight across the marine area. A
trough of low pressure east of the state will weaken and shift
eastward on Friday, shifting winds around to a more typical trade
wind direction and easing speeds back to moderate levels by late in
the day. Model solutions indicate a brief wind surge may pass
through the islands from north to south late Friday night and
Saturday, and this may kick the trades back up to strong levels
across portions of the marine area. Behind the wind surge, moderate
trades should then hold in place Saturday night through early next
week as high pressure holds in place to the north of the island
chain. The gradient appears to tighten a bit Tuesday through late
next week, and this may increase trades back into the moderate to
strong range.

A Small Craft Advisory (SCA) remains in effect for all waters
through Friday, due to winds, seas, or a combination of the two.
Winds will begin to drop off Friday through the weekend, with the
direction shifting around to a more typical trade wind direction.
Seas will remain elevated across portions of the marine area right
through the weekend however, due to a series of west-northwest
swells moving through the area.

A High Surf Advisory (HSA) remains in effect for east facing shores
of most islands through 6 AM Friday due to a large northeast wind
swell. This HSA will likely need to be extended through Friday night
and possibly into Saturday, with the swell then slowly fading
through the remainder of the weekend. Surf heights may once again
pick up along east facing shores toward the middle of next week.

A HSA also remains in effect for most north and some west facing
shores through 6 AM Friday, due to a moderate size west-northwest
swell moving through the area. This swell will gradually lower
Friday and Friday night. Another moderate size west-northwest swell
is expected to fill on Saturday, peak late Saturday and Saturday
night, then lower gradually on Sunday. Surf heights may reach HSA
levels along some north and west facing shorelines. A slightly
smaller west-northwest swell is on tap for Monday and Tuesday with a
slightly larger west-northwest swell expected Tuesday night and
Wednesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until midnight HST tonight for Kauai-Oahu-Molokai-
Lanai-Kahoolawe-Maui Leeward West-Maui Central Valley-Kohala.

High Surf Advisory until 6 AM HST Friday for Niihau-Kauai
Windward-Kauai Leeward-Oahu North Shore-Oahu Koolau-Olomana-
Molokai-Maui Windward West-Maui Central Valley-Windward
Haleakala-Kona-Big Island North and East.

Small Craft Advisory until 6 PM HST Friday for Oahu Leeward
Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-
Big Island Leeward Waters-Big Island Southeast Waters.

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

&&

DISCUSSION...Hui
AVIATION...Bohlin
MARINE...Jelsema