High Wind and High Surf in Hawaii, August 30 to 31, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
553 AM HST TUE AUG 30 2016

.UPDATE...
Quick forecast update to include a Tropical Storm Warning for the
Big Island and Tropical Storm Watch for Maui county. The Hurricane
watch remains in effect for the Big Island as well.

&&

.SYNOPSIS...
Moisture will increase from east to west across the state today
in advance of Hurricane Madeline, with showers favoring windward
and mauka locales. Direct impacts from Hurricane Madeline,
including damaging winds, flooding rain, and high surf, are
expected over the Big Island and possible over other portions of
the state Wednesday through Thursday. After a brief return of
stable trade wind weather, Hurricane Lester may affect the islands
over the upcoming Labor Day weekend.

&&

.PREV DISCUSSION.../ISSUED 359 AM HST AUG 30 2016/

Currently at the surface, Hurricane Madeline is located around
450 miles east of Hilo, while Hurricane Lester is around 1375
miles to the east of the Hilo. Meanwhile, the two weather systems
driving the moderate to locally breezy trade wind flow across the
island chain this morning are a 1027 mb high around 1250 miles
north of the state and Invest 92C around 500 miles southwest of
Honolulu. Infrared satellite imagery shows partly cloudy skies in
place in most areas, with increasing cloud cover upstream of
windward sections of Maui and the Big Island. Radar imagery shows
isolated to scattered showers drifting into windward areas, with
mainly rain free conditions elsewhere. Main short term concern
over the next few days continues to revolve around the impacts
Madeline will bring to the Aloha state.

Today and tonight,
Rainfall will increase through the day as a broad band of
moisture on the periphery of Hurricane Madeline moves over the
islands from east to west. Mid level ridging will maintain
relatively stable conditions, with the bulk of the moisture below
12 kft. As a result, moderate trade winds will focus clouds and
showers over windward slopes, though some showers will be carried
across leeward areas at times.

Wednesday through Sunday night,
The main concern heading into Wednesday and Thursday will be the
impacts from Hurricane Madeline. The latest track from the
Central Pacific Hurricane Center (CPHC) shows Madeline moving near
the Big Island Wednesday afternoon through Thursday morning, and
a Hurricane Watch and Flash Flood Watch remain in effect for that
island. While the highest chances of damaging winds, flooding
rainfall, and large dangerous surf are on the Big Island, any
change in the track could mean that additional portions of the
state will experience direct impacts and could be placed under a
watch or warning. For this reason, it is important to not focus
too closely on the exact forecast track of Madeline, especially
since the average forecast track error is about 85 to 150 miles in
the 48 to 72 hour time range. It is also important to note that
significant impacts can extend well away from the center of a
tropical cyclone. Please refer to the Hurricane Madeline Local
Statement (HLSHFO) for details.

Distant Hurricane Lester may threaten the state during the
Holiday weekend. It is far too early for specifics at this time,
and all islands have roughly equal chances of experiencing direct
impacts from Lester. Residents and visitors are urged to closely
monitor the latest forecasts from the CPHC and NHC regarding these
tropical cyclones.

Monday,
Both the 00z GFS and 00z ECMWF are in good agreement showing deep
layered ridging building well north-northeast of the islands. This
should allow a drier and more stable trade airmass to spread from
east to west across the state, bringing a return of more typical
trade wind weather to the Aloha state.

AVIATION...
VFR conditions will mostly prevail across the terminals through
the TAF period as moderate to locally breezy trade winds continue
today. The exception to VFR conditions will be with isolated MVFR
conditions in trade wind showers. After 00z, coverage of showers
will begin to increase from east to west, as a band of moisture
pushes in ahead of Hurricane Madeline.

As Hurricane Madeline approaches from the east, it will begin to
tighten the pressure gradient with high pressure to the north.
This will allow for breezy northeasterly trade winds to gust
today and likely continue to gust at times to 25-30 kts at
windward terminals tonight.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory from 6 PM this evening to 6 AM HST Thursday
for Kauai Windward-Oahu Koolau-Olomana-Molokai Windward-Maui
Windward West.

Hurricane Watch for Big Island.

Tropical Storm Warning for Big Island.

Flash Flood Watch from Wednesday morning through late Thursday
night for Big Island.

Tropical Storm Watch for Molokai-Lanai-Kahoolawe-Maui.

High Surf Warning until 6 AM HST Thursday for Windward Haleakala.

Hurricane Watch for Alenuihaha Channel-Big Island Windward
Waters-Big Island Leeward Waters-Big Island Southeast Waters.

Tropical Storm Warning for Alenuihaha Channel-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Waters.

Tropical Storm Watch for Maui County Windward Waters-Maui County
Leeward Waters-Maalaea Bay-Pailolo Channel.

&&

UPDATE...Jelsema