Drought in Hawaii, November 1 to 30, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Mon Oct 31 2016

.SYNOPSIS...
A surface ridge north of the state will drive breezy and gusty
trade winds into Tuesday, followed by a slight decrease in the
trades for the remainder of the week. A somewhat dry and stable
air mass will produce modest windward rainfall through the week,
and aside from a few afternoon showers across the Kona slopes of
the Big Island, leeward areas will be rather dry.

&&

.DISCUSSION...
Mainly dry conditions prevail across the Aloha State on this
Monday evening. Radar shows just passing light showers across
a few windward areas, with showers most common along the Hamakua
coast on the Big Island. Surface analysis depicts an east-west
oriented high pressure ridge located about 500 miles north of the
state. This ridge extends southeast from a strong 1034 mb high
centered far to our northwest. Gusty trade winds prevail over the
islands within a tight pressure gradient to the south of the
ridge. During the day and into the evening, wind gusts at most
locations have been in the 30-40 mph range, with a few peak gusts
over 40 mph at the windiest locations influenced by terrain.
Aloft, an elongated upper level trough stretches west-southwest
across the state. This trough appears to be weakening in water
vapor imagery, with a strong mid level ridge building eastward
from the international date line. MIMIC-TPW and infrared satellite
imagery shows a dry airmass over and extending far to the
northeast/east of the state, with estimated PW values around or
below one inch and a large field of stratocumulus over the waters
to our northeast. The 00Z soundings depict strengthening and
lowering trade wind inversions based between 5000 and 8000 feet,
along with PW values ranging from 0.9 to 1.2 inches.

Overnight, expect breezy/gusty trade winds to continue along with
mainly dry conditions. Passing showers will produce light rainfall
amounts over some windward areas, with most leeward areas
remaining dry. Windward Big Island will likely see the most
rainfall due to some lingering low level moisture, but even there
expect only light to locally moderate rainfall. The existing
forecast appears to be on track, and no updates are planned for
this evening.

The breezy trade winds will decrease a notch from late Tuesday
into Wednesday. A strong jet stream running across the north
Pacific will keep the subtropical ridge slightly weakened and
displaced a bit south of normal over the central Pacific. This
will cause trades to back off slightly into the moderate to
locally breezy range through the middle and later part of the
week.

Rather dry trade wind weather is forecast to prevail through the
rest of this week and the upcoming weekend. The latest global
models show PW values hovering around to just over one inch,
or about 25 percent below normal. The remnants of an old front
may approach Kauai on Thursday, but models suggest that this will
have little impact, with perhaps just a minor increase in windward
shower activity. A building mid level ridge over the state will
create increasingly stable conditions, which combined with the
limited moisture availability will limit trade shower activity.
Expect passing showers across windward areas, with mainly dry
conditions leeward.

&&

.AVIATION...
High pressure north of the state will keep breezy to locally
windy trades in place through Tuesday, with clouds and showers
focused primarily over windward and mauka areas. Brief MVFR
cigs/vsbys are possible in passing -SHRA across windward locales,
but predominantly VFR conditions are expected through 02/12Z.

AIRMET Tango remains in effect for low level turbulence over and
downwind of the mountains, as well as for upper level turbulence
due to a jet stream over the islands.

&&

.MARINE...
Strong trade winds will continue into Tuesday, with trade winds
remaining at near gale strength over the typically windy waters
around the Big Island and Maui tonight. A morning ASCAT pass
missed the eastern half of the islands but showed widespread 25 kt
winds holding around Kauai and Oahu. With only a slight decrease
in winds expected tonight, the Small Craft Advisory (SCA) for all
waters remains posted through the night. The SCA will remain in
place for most waters on Tuesday and will likely be trimmed back
to the typical windier locations by mid to late week as the trades
ease a notch.

A High Surf Advisory remains posted for most east facing shores.
Some of the windward PacIOOS buoys are starting to show a slight
decline in trade wind driven seas early this evening. NOAA buoy
51000, located a couple hundred miles northeast of the islands,
shows seas continuing to decline, and we expect to see this
decline show up at the nearshore buoys later tonight. The High
Surf Advisory has been extended through the night. Surf along east
facing shores was barely at advisory levels at a few reporting
locations today, and should be below advisory levels on Tuesday.
A gradual decline will occur during the next couple of days, with
trade wind energy holding at 5 to 7 ft at 8 seconds from Tuesday
through the weekend.

A moderate northwest swell arriving on Tuesday will be reinforced
late Wednesday and late Thursday by a pair of large north-
northwest swells. Resulting north shore surf will be well above
advisory levels late Wednesday through Friday, and at its short-
lived peak, warning level surf will be possible Wednesday night
and Thursday.

&&

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

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

Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters.

&&

DISCUSSION/MARINE...Jacobson
AVIATION...Jelsema