High Surf in Hawaii, January 4 to 7, 2017

Area Forecast Discussion
National Weather Service Honolulu HI
353 AM HST Wed Jan 4 2017

.SYNOPSIS...
Moisture associated with a remnant frontal boundary will slowly
move down the island chain today through Friday, bringing an
increase in showers particularly to windward and mauka areas as
it moves through. Cool and dry conditions are expected once the
remnant frontal boundary passes through, with these conditions
lingering into early next week.

&&

.DISCUSSION...
Currently at the surface, the remnants of a dissipated frontal
boundary are somewhere in the vicinity of Kauai and just to the
north of Oahu early this morning. Infrared satellite imagery shows
a broken band of clouds and showers extending from Niihau and Kauai
eastward to the north of Oahu and Maui County, with radar imagery
showing most of the shower activity in this area. Main short term
concern for the next couple days revolves around rainfall chances
associated with the frontal remnants moving slowly southward down
the island chain.

Today,
The remnants of an old frontal boundary will shift slowly
southward through Kauai, reaching Oahu by late this afternoon.
The airmass in advance of the front remains very dry, with MIMIC
total precipitable water (PW) imagery showing values between 0.75
and 1.0 inches. PW values do increase along and behind the remnant
frontal boundary however, with values generally in the 1.1 to 1.3
inch range. As a result, we should see a wet day across Kauai,
with conditions deteriorating over Oahu by late this afternoon.
The showers over Oahu and Kauai will be most prevalent in windward
and mauka areas, but due to the deeper moisture associate with
the remnant frontal boundary and increasing northeasterly trades,
some of the shower activity will reach leeward areas as well.
Across Maui County and the Big Island, conditions are expected to
remain fairly dry, with isolated to scattered showers favoring
windward locales. Isolated showers will be possible in leeward
areas of Maui County and the Big Island as well, due to the
assistance of daytime heating.

Tonight through Friday,
The remnant moisture associated with the front will continue to
slowly shift southward down the island chain through the period.
The frontal remnants are expected to move through Oahu and into
Maui County by late tonight, with the boundary becoming
increasingly more diffuse as it lingers over Maui County on
Thursday. The frontal remnants will then push southward into the
Big Island on Friday. There will be an increase in clouds and
showers in association with the front as it moves through the
islands, particularly in windward and mauka areas. Behind the
frontal remnants, a cooler and more stable airmass will move in,
with leeward areas clearing out while clouds and showers hang on a
bit longer in windward locales.

Friday night through next Tuesday,
A relatively dry and stable weather pattern is expected to
continue through the period as high pressure far to the north of
the islands Friday night shifts to a position well northeast of
the state on Sunday. This will keep a light to moderate north to
northeast trade wind flow in place through Sunday, with showers
primarily limited to windward and mauka areas. Another cold front
will begin to approach from the northwest early next week, but it
appears that this front will stall out to the north of the island
chain. This will weaken the trade wind flow across the islands
however, with some areas experiencing land and sea breezes.
Showers will continue to favor windward areas, with rain chances
remaining below climatological norms.

&&

.AVIATION...
A front appears to be washing out as diffuse, showery low cloud
elements move over Kauai and Oahu from the northeast this early
morning. VFR will predominate over the state today, with brief
MVFR conditions possible in lower ceilings and showers in
windward and mauka areas, especially from Kauai to Maui. Northeast
winds will remain light to moderate as the frontal remnants push
south and east.

An AIRMET for mountain obscuration is currently in effect for
Kauai, though it will likely be cancelled at the next issuance
time.

&&

.MARINE...
There has been a slight increase in northeasterly winds across
the waters north of Kauai and Oahu as a remnant frontal boundary
pushes slowly southward across the area this morning. As a result
of these stronger winds and a north swell spreading down across
the island chain, combined seas have increased to around 10 feet
at the Hanalei and Waimea Bay buoys. Therefore, a Small Craft
Advisory (SCA) has been issued for the Kauai Northwest and
Windward Waters, the Kauai Channel and the Oahu Windward Waters
through this morning. This SCA may need to be extended into this
afternoon if seas do not subside as quickly as anticipated.
Otherwise, winds and seas are forecast to remain below the SCA
criteria into this weekend across all Hawaiian waters, since
gentle to moderate north to northeast winds are expected to
prevail across the coastal waters from tonight through Saturday.

The current north swell appears to have peaked at National Data
Buoy Center (NDBC) buoys 51001 / 51101 located northwest of Kauai.
The swell height currently appears to be at least 2 feet above
the Wave Watch III model guidance at the buoys immediately north
of the islands. The swell direction is forecast to shift out of
the north-northeast as it peaks later today. As a result, a High
Surf Advisory remains in effect for east facing shores of Kauai,
Oahu, Molokai, Maui and the Big Island through this afternoon.
This is mainly for beaches and reefs along east facing shores with
an exposure to the north. This swell is forecast to gradually
subside from tonight through Thursday.

A new north-northeast swell, which is expected to arrive Thursday
evening, may cause surf to reach the High Surf Advisory criteria
along east facing shores with an exposure to the north again
starting Friday. This swell is expected to linger through Sunday.

A small, but long period south-southwest swell will continue today.
This swell is producing a slight bump in surf heights along most
south facing shores across the state.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST this evening for Kauai
Windward-Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-
Windward Haleakala-Big Island North and East.

Small Craft Advisory until noon HST today for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Channel-Oahu Windward Waters.

&&

DISCUSSION...Jelsema
AVIATION...Kinel
MARINE...Houston