Drought in Hawaii, November 29 to 30, 2016

Area Forecast Discussion
National Weather Service Honolulu HI
836 PM HST Mon Nov 28 2016

.SYNOPSIS...
Breezy to strong trade winds will bring limited showers to
windward and mountain areas through Tuesday. Showers will increase
starting Tuesday night as an upper low moves over the area
bringing the possibility of locally heavy showers. Trade winds
will decrease Friday with lighter winds and wet weather on tap
through the weekend.

&&

.DISCUSSION...
High pressure centered far northeast of the state is producing breezy
trade winds over the islands. The high will merge with a second
transient high Tuesday bringing breezy to windy conditions to the
islands Tuesday through Thursday.

Rainfall amounts will remain near average through Tuesday, and
showers will fall mainly over windward and mountain areas.
Rainfall chances will increase Tuesday night and through the week
as increasing moisture moves into the eastern half of the state,
and an upper level trough brings instability to the atmosphere.
The moisture and instability combined with the trade winds will
increase showers across the state. Rainfall will focus over
windward and mountain areas, but leeward locations will see
increasing showers as well. The instability aloft will allow our
normally capped trade wind clouds to grow vertically, bringing
more intense showers and the possibility of brief thunderstorms
over windward areas.

The upper low will bring colder than normal temperatures to the
middle and upper atmosphere, and temperatures at the summits of
the Big Island will hover near freezing. Any precipitation that
falls at the summits from Tuesday night into the weekend will be a
mix of rain, snow, and ice. The Big Island leeward slopes will
see more intense afternoon showers due to the instability aloft
starting Wednesday and this trend will continue into the weekend.
The potential for thunderstorms have been added to the forecast
for the Big Island leeward slopes Wednesday afternoon with
significantly colder temperatures aloft expected.

In the extended forecast, global weather models are depicting troublesome
weather for the weekend as a second upper level low drops south
near the islands. The upper low will reinforce the instability and
cold temperatures already in place over the state. This will
maintain a wet weather pattern through the weekend with the
potential for heavy showers and the possibility of thunderstorms.
The details from the models solutions have converged somewhat
over the past 24 hours, with the GFS and ECMWF now placing the upper
low west of Kauai by Sunday afternoon. This placement would bring copious
amounts of tropical moisture over the state, bringing the
potential for widespread rains and the possibility of flooding
from Saturday into early next week. However, long range forecasts
have a tendency to be highly variable so stay tuned as the details
of the forecast become illuminated as the weekend approaches.

&&

.AVIATION...
Breezy trade winds will increase further across the state through
Tuesday. Clouds and showers will remain focused on windward coasts
and slopes, but some showers will spill over into leeward areas.
Localized MVFR will be possible windward, otherwise VFR conditions
will prevail. There is a chance that AIRMET SIERRA for mountain
obscuration may become necessary for some windward areas later
tonight or Tuesday.

AIRMET TANGO remains in effect for moderate low level turbulence
over and downwind of the terrain. These conditions are likely
to continue through Tuesday.

&&

.MARINE...
Due to locally strong trade winds and elevated short-period seas,
a Small Craft Advisory (SCA) remains in effect for most coastal
waters this evening. Trade winds are expected to increase Tuesday,
and remain strong and gusty through Thursday as high pressure
builds far north of the area. As a result, the SCA has been issued for
all Hawaiian waters starting Tuesday morning, except for the
Alenuihaha and Pailolo channels where a Gale Watch is in effect.
This Gale Watch may need to be upgraded to a Gale Warning later
tonight. In the longer term, we expect a significant weakening of
wind speeds by this weekend, since a surface trough may develop in
the vicinity of the islands. However, confidence remains low as to
the details of this feature.

The strong trade winds will continue to maintain elevated short-
period surf from the east through mid-week. As a result, a High
Surf Advisory remains in effect through Thursday for east facing
shores of most islands. A low with hurricane-force winds is
currently racing toward northeast across the northwest Pacific,
and the associated fetch will likely send a significant long-
period northwest swell toward the islands. This swell is expected
to spread across the island chain Thursday, and peaking Friday.
As a result, a High Surf Advisory will likely be required along
most north and west facing shores Thursday night and Friday.

A small south-southwest swell is producing a modest boost in surf
heights along south facing shores tonight, and is expected to
gradually diminish during the next couple of days. The Oahu Surf
Discussion (SRDHFO) has been updated and contains details on the
swell sources and their expected evolution.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 PM HST Thursday 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 AM HST Thursday for Kauai Windward
Waters-Oahu Windward Waters-Kaiwi Channel-Maui County Windward
Waters-Maalaea Bay-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.

Gale Watch from Tuesday morning through Wednesday afternoon for
Pailolo Channel-Alenuihaha Channel.

Small Craft Advisory until 10 AM HST Tuesday for Pailolo Channel-
Alenuihaha Channel.

Small Craft Advisory from 6 AM Tuesday to 6 AM HST Thursday for
Kauai Northwest Waters-Kauai Leeward Waters-Kauai Channel-Oahu
Leeward Waters-Maui County Leeward Waters.

&&

Morrison...Discussion
Houston...Marine
Jacobson...Aviation