National Weather Service Raw Text Product

689 
FXHW60 PHFO 090620
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
820 PM HST Mon Jul 8 2019

.SYNOPSIS...
A high pressure ridge far north of the state will keep trade 
winds in the forecast through the next seven days. The remnants of
former tropical cyclone Barbara will drift westward overnight with
continued wet weather lasting into Tuesday. More stable drier
trends are expected from Wednesday through Friday with wet trade 
wind weather returning to the southeastern islands over the 
upcoming weekend.

&&

.DISCUSSION...
A high pressure ridge far to the north of the state will keep
trade winds in the forecast for the foreseeable future. 
Meanwhile, deep tropical moisture associated with the remnants of 
former tropical cyclone Barbara continue moving westward just 
south of the main Hawaiian Islands. The center of this system is 
located roughly 300 miles southwest of the Big Island this 
evening. Strong trade winds will gradually decrease tonight and 
tomorrow and the Wind Advisories for Hawaii and Maui counties were
cancelled. Numerous showers continue to spread across the state 
this evening as unstable cloud bands drift into each island in 
moderate trades. The trough axis associated with Barbara will pass
just to the west of the state by Tuesday morning, however a 
second trough shown on 700 mb streamlines will keep enough 
tropical moisture around for continued wet trade wind showers 
lasting through Tuesday night.

Wednesday through Friday, the large scale weather pattern changes
on Wednesday as a stronger ridge aloft causes increased downward 
vertical motions and lower trade wind inversion heights. This 
means shower activity will trend lower with clouds and showers 
favoring windward and mountain slopes. By Thursday the trade wind 
inversion heights will fall into the 5000 to 7000 foot range, 
capping cloud development and shower activity. A drier trade wind 
weather regime will continue for all islands through Friday 
afternoon.

On Saturday and Sunday, another tropical disturbance develops far
south of the Big Island. Long range model solutions continue to
track this system northwestward into the Hawaii region on Sunday.
Another plume of deep tropical moisture will advect into Hawaii
and portions of Maui counties likely heralding another round of
wet trade wind weather for at least the southeastern islands.
Both global models are showing a wet weekend weather pattern for 
the Big Island and windward Maui lasting into the first few days
of next week. 

&&

.AVIATION...
High pressure north of the state and the remnants of former 
Tropical Cyclone Barbara passing by to the south, will keep
moderate to breezy easterly trade winds in place through Tuesday. 
As a result, AIRMET Tango remains in place for low level
turbulence over and downwind of the terrain of all islands. These
conditions will likely continue through Tuesday.

Deep tropical moisture will linger over the islands tonight and
Tuesday, bringing MVFR cigs/vsbys to windward areas in passing 
showers. AIRMET Sierra is in effect for windward sections of all
islands, and will likely continue through the night. Some
improvement is possible Tuesday. VFR conditions should prevail in
leeward areas.

&&

.MARINE...
A surface trough, which is the remnant of former East Pacific 
Tropical Cyclone Barbara, is located about 165 nm south of 
Honolulu. This feature has been moving westward at 10 to 15 kt, 
and its close proximity to the islands continues to keep the 
pressure gradient very tight across the area early this evening. 
As a result, the trade winds are strong across most areas. In 
addition, the strong winds are producing elevated rough seas. A 
Gale Warning remains in effect through early Tuesday morning for 
the Alenuihaha Channel and the waters south of the Big Island. 
Elsewhere, a Small Craft Advisory (SCA) continues for the 
remaining coastal waters. As the surface trough continues to move
west of the area, the trade winds are expected to begin to weaken
on Tuesday. Later this week, high pressure is forecast to build 
north of the state, so SCA winds will likely return to the 
typically windier waters adjacent to the islands of Maui County 
and the Big Island starting around Thursday.

The strong trade winds continue to produce large waves along east
facing shores, especially over the eastern end of the state. A 
High Surf Warning remains in effect for east facing shores of the 
Big Island through early Tuesday morning. A High Surf Advisory 
(HSA) also remains in effect for east facing shores of most of 
the smaller islands through early Tuesday morning. We will monitor
observations from the nearshore buoys overnight in case we need 
to extend the HSA for east facing shores during the day on 
Tuesday. Otherwise, surf will continue to lower along east facing 
shores from Tuesday night through this weekend.

The combination of a declining south-southwest swell and a small
southeast swell generated by strong southeast trade winds in the 
South Pacific last week will likely maintain surf heights near or 
slightly above the summer-time average along exposed south facing
shores through mid-week. New long period south-southwest swells 
arriving starting Friday are expected to cause surf to reach the 
HSA criteria along south facing shores next weekend. This 
elevated surf may require the HSA to continue into early next 
week.

Elsewhere, a small northwest swell is expected to arrive late
Wednesday. This swell may produce a slight bump in surf along
north and west facing shores of some of the smaller islands from 
Wednesday night through Friday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Tuesday for east facing shores
of Maui Molokai Oahu and Kauai.

High Surf Warning until 6 AM HST Tuesday for east facing shores of
the Big Island.

Gale Warning until 6 AM HST Tuesday for Alenuihaha Channel-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-Oahu Leeward Waters-Kaiwi Channel-Maui 
County Windward Waters-Maui County Leeward Waters-Maalaea Bay-
Pailolo Channel-Big Island Windward Waters.

&&

$$

DISCUSSION...Bohlin
AVIATION...Jelsema
MARINE...Houston