Wildfire in Hawaii, March 10 to 11, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
850 PM HST Sat Mar 9 2019

.SYNOPSIS...
Breezy to locally windy trades are expected to prevail through
early Monday, with the trades easing late Monday and Monday night.
Moderate trades will prevail Tuesday through Thursday, before
becoming light Friday into next weekend. Periods of wet weather
will move through the islands tonight through early Monday, with
windward and mauka areas being the favored targets. A more typical
trade wind shower pattern will return later Monday through
Thursday, with clouds and showers continuing to favor windward
and mauka areas, particularly during the overnight and early
morning hours. Drier conditions are expected Friday into next
weekend.

&&

.DISCUSSION...
Currently at the surface, a 1032 mb high centered around 1000
miles northeast of Honolulu, is driving breezy trade winds across
the island this evening. Infrared satellite imagery shows mostly
cloudy skies east of Oahu, largely due to the broken jet stream
cirrus streaming overhead. Meanwhile across Oahu and Kauai, mostly
cloudy conditions are present in windward areas with partly
cloudy conditions in leeward locales. Radar imagery shows
scattered to numerous showers moving into windward areas, with
some of the showers reaching leeward areas at times as well. Main
short term focus continues to revolve around the strong trades
and rainfall trends.

Model solutions remain in excellent agreement with the large
scale synoptic pattern through the forecast period. High pressure
will remain nearly stationary around 1000 miles northeast of the
island chain tonight through Sunday night, before beginning to
track eastward on Monday. The high will then accelerate towards
the west coast of the continental United States Monday night
through Wednesday as a cold front passes by to the north of the
islands. The front will stall out and dissipate around 400 to 500
miles north of Kauai Wednesday night, with a surface ridge axis
settling slowly southward through the remainder of the work week
and over the western and central islands next Saturday.

Breezy to locally windy conditions are expected to prevail through
through Monday, although the trade wind speeds should edge
slightly lower on Monday. The trades will continue to trend
downward Monday night, then hold in the moderate range Tuesday
through Thursday, before becoming light Friday into next weekend.

A band of showery low clouds moving into the islands this evening
will linger through Monday morning, bringing periods of fairly
wet weather to windward areas, with more regular leeward spillover.
The showers will likely be most prevalent at night into the early
morning hours. Fairly typical trade wind weather is expected
statewide from late Monday morning through the remainder of the
work week, with some decrease in shower coverage likely toward the
end of the week into next weekend as upper level heights build
and the surface ridge axis settles southward. Showers will
continue to favor windward and mauka areas with a few showers
reaching leeward communities from time to time.

High clouds associated with a subtropical jet stream will hold
over the central and eastern islands tonight and Sunday, although
some thinning of the cirrus is indicated by model time/height
relative humidity cross sections through the day on Sunday. The
high clouds are then expected to retreat eastward Sunday night.

&&

.AVIATION...
Surface high pressure northeast of Hawaii will keep moderate to
possibly strong east-northeasterly trade winds in place through
the period. AIRMET Tango for low-level turbulence below 8,000 ft
remains in place and is expected to remain through Sunday. There
is also the possibility for upper level moderate to severe
turbulence from FL270 to FL420 due to the upper-level trough in
place over the state stretching east-northeast of Hawaii.

There is low-level moisture over Kauai therefore AIRMET Sierra for
mountain obscuration is in effect above 1,500ft due to clouds and
possible showers. MVFR conditions will begin to spread south and
effect windward slopes so AIRMET Sierra may need to be extended
to other islands as we progress through the night into Sunday.
Otherwise most leeward areas in the state will continue to see VFR
conditions.

&&

.MARINE...
Strong trade winds associated with high pressure centered north-
northeast of the state will continue through Sunday night, then
gradually begin to trend down into the moderate to locally strong
category through the first half of the week as a weakness in the
ridge develops. Satellite data earlier today over the eastern end
of the state showed 20 to 30 knots, strongest over the Alenuihaha
Channel and waters around South Point. A combination of strong
winds locally and upstream of the state along with a moderate
northwest swell have led to advisory-level seas over exposed
waters. The latest buoy observations showed seas running near to
slightly above predicted levels (Hanalei PacIOOS buoy spiked to 14
ft early this evening/Hilo up to 11 ft). Seas will remain rough
through Monday, then gradually begin to ease by midweek as the
winds locally and upstream trend down.

Surf along north and west facing shores will hold at advisory
levels through Sunday then drop below on Monday. Overlapping
reinforcements, however, expected out of the same general
direction Monday, Thursday and Friday night from activity over
the northwest Pacific will be enough to keep the surf up each day
through next weekend. The first reinforcement will fill in
through the day Monday and peak by Monday night, then lower into
midweek. The second one is expected to begin filling in Thursday,
peak by Thursday night, then lower into the weekend. Heights
should remain below advisory levels as these sources peak. The
third reinforcement expected to fill in Friday night will be much
smaller, but hold into the weekend. For the long range, guidance
shows a gale low tracking southeast across the Date Line Friday
through Saturday. A captured fetch associated with this source
setting up within the 310 to 340 directional bands relative to
the islands could drive the surf up locally by the end of next
weekend.

Surf along east facing shores will remain rough into the upcoming
week due to the strong onshore winds, likely holding around advisory
levels through Monday and possibly into Tuesday before lowering.
This downward trend will continue through the week and into next
weekend as the upstream fetch weakens and the local winds drop
into the light to moderate category.

The first south swell of the season has filled in along south facing
shores from recent activity across the southern hemisphere within
Hawaii's swell window. This swell will peak Sunday below advisory
levels, then gradually lower through the first half of the week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until noon HST Sunday for Niihau-Kauai
Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu
Koolau-Olomana-Molokai-Maui Windward West-Windward Haleakala.

Small Craft Advisory until 6 PM HST Monday for all Hawaiian
waters-

&&

DISCUSSION...Jelsema
AVIATION...Chevalier
MARINE...Gibbs