Wildfire in Hawaii, January 6 to 8, 2019

Area Forecast Discussion
National Weather Service Honolulu HI
334 PM HST Sun Jan 6 2019

.SYNOPSIS...
Wind will fluctuate through the forecast period as weak fronts
approach, but not quite reach, the main Hawaiian island chain.
Scant showers will affect mainly windward areas during periods of
trade flow, shifting to mauka areas each day during periods of
light and variable winds. Southeasterly winds will settle over the
islands next weekend.

&&

.DISCUSSION...
The subtropical ridge just north of the main Hawaiian islands is
being pushed eastward by a frontal boundary far to our northwest.
Local winds have decreased, with light and variable speeds noted
over waters west of Maui. Light east-southeasterlies prevail
elsewhere. Afternoon soundings show a dry and stable airmass over
us, with PW values far below an inch and with positive lifted
index values. A strong subsidence inversion near 5400 feet is also
noted. Satellite loop shows a field of broken stable low clouds
extending eastward from about 155W, with patchy breakaway elements
reaching the islands within the light east-southeast flow. Radar
shows almost no shower activity across the islands this afternoon.

We expect winds will become light and variable statewide tonight
as the subtropical ridge axis edges southward over us. Moisture is
quite limited and strongly capped, so any windward cloud and
shower coverage shifting to mauka areas will be limited as well.
The ridge will shift northward Monday, allowing light to moderate
trade flow to briefly return. A weak frontal boundary will
approach Kauai Monday night, stalling just along the northern
fringe of that island before retreating back northward early
Tuesday. Winds will veer to light southeasterlies once again on
Tuesday ahead of the front, but continued stable conditions should
keep rainfall light and focused mainly across windward and
southeast-facing areas. Winds will be light and variable across
the area on Wednesday within an almost flat pressure gradient.
Models show a repeat pattern later in the week, with a weak front
expected to approach Kauai late Wednesday into Thursday, then
stall just to the north. A noticeable difference will be a return
to trade flow Thursday and Friday across local waters south of
this second front as the ridge will be stronger to our east.

Later on Friday, models show the trades giving way to
southeasterly winds across western portions of the island chain as
yet another front tries to approach the islands from the
northwest. This southeasterly flow will persist into next weekend
as high pressure develops east of the islands and the front
lingers to our west and northwest.

&&

.AVIATION...
Light flow will prevail through this evening as a weak front
approaches from the northwest. After sun down, expect land breezes
to ensue across the islands. By Monday afternoon, however,
typical light to moderate northeasterly trades are progged to
return to the area. Isolated showers will be limited to mainly
the windward slopes and mountain ridges through late this
afternoon, then transition to out over the coastal waters by
tonight.

No AIRMETS are currently in effect.

&&

.MARINE...
Winds are expected to remain below Small Craft Advisory (SCA) levels
through Friday as several weak highs and fronts pass eastward
north of the area. Seas will also remain below SCA criteria due to
the lighter winds and no large open ocean swells expected to pass
through the area.

Areas of low pressure moving westward across the N Pacific will
cause a series of small NW swells through most of this week. Surf
heights are expected to remain below High Surf Advisory (HSA) levels.
A much larger NW swell is expected Friday night through Sunday
with advisory or warning level surf expected. Short period choppy
surf will gradually diminish over the next few days along E facing
shores due to diminished trade winds. A small NNE swell is
expected to fill in Tuesday night and Wednesday, then linger on
into Friday. Surf heights may reach HSA levels along E facing shores
during the peak of the swell.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION...Powell
AVIATION...JT
MARINE...Burke