485 
FXHW60 PHFO 100618
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
818 PM HST Thu May 9 2019

.SYNOPSIS... 
Light trade winds will continue into the weekend with land and sea
breezes favoring leeward coasts, and isolated afternoon through
early evening showers. A weak disturbance aloft will drift through
the islands, from Sunday afternoon into Monday, producing a 
slight bump in windward clouds and showers. Trade wind speeds will
pick up by the middle of next week as a high pressure system
builds in north of the state.

&&

.DISCUSSION...
A weak low level trough roughly 400 miles northeast of the main
Hawaiian Islands will linger over the region and help weaken the
surface pressure gradients and trade wind flow through the 
upcoming weekend. Light trade winds will last into the weekend
with land and sea breezes favoring windward slopes. A high pressure 
ridge aloft will continue to cap vertical cloud development over 
most of the state around 6000 feet and keep fair weather in the 
forecast due to moderate subsidence through Sunday afternoon.
Clouds will tend to form over interior sections each day with 
cloud bands forming along light trade wind and sea breeze 
convergence zones. Isolated showers are possible mainly over 
interior sections in the afternoon and early evening hours as
surface heating decreases. Clouds and showers will diminish in 
the evening hours as offshore land breezes develop.

A weak upper level short wave trough will drift into the region 
from the northwest from Sunday night through Monday. A slight 
increase in cloud heights and showers is projected on the American
(GFS) and European (ECMWF) models, mainly over the windward 
slopes of Maui and the Big Island as a passing surface trough 
interacts with this upper level short wave. Both models are in
good agreement with increasing shower trends for both islands.

High pressure will build back in north of the state from Tuesday
into Wednesday with a return to moderate trade winds along with an
increase in windward and mauka shower activity. There remains a
good chance these refreshing moderate trade winds will stick 
around from Wednesday through the end of next week.

&&

.AVIATION...
Light northeasterly trades will prevail through the night. Though
conditions remain rather dry, ISOL -SHRA are forecast to affect 
mainly the western smaller islands and northeastern portions of 
the Big Island. Otherwise, expect VFR conditions.

No AIRMETS are anticipated tonight. 

&&

.MARINE...
A surface ridge far northwest of Kauai will maintain northeast 
trade winds over the Hawaiian coastal waters. However, a trough 
northeast of the area will keep the trade-wind speeds low to
occasionally moderate through Monday morning. The prevailing 
winds will be light enough to allow nighttime offshore land 
breezes and onshore daytime sea breezes near the islands. The 
trough will dissipate early next week and a new high will build in
from the northwest. Trade winds will strengthen starting Monday 
afternoon. Winds could reach Small Craft Advisory levels by the 
middle of next week.

A small northwest swell will slowly subside through Sunday. A 
small south swell is expected to fill in through Friday. A larger
south swell generated well southeast of New Zealand could produce
surf approaching the advisory level along south facing shores 
early next week. Small southeast swells will persist through the 
middle of next week, but the Big Island will block some of the 
swell from reaching the smaller islands. Surf will remain quite 
small along east facing shores due to the light trade winds.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Bohlin
AVIATION...JT
MARINE...Kinel