Weather Service Report


848 
FXHW60 PHFO 230610
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
810 PM HST Wed Sep 22 2021

.SYNOPSIS...
Breezy trade winds will continue through the weekend, with clouds 
and showers favoring windward and mauka locations overnight through 
the morning periods. Very little moisture making it into leeward 
areas will translate to the drought conditions prevailing. A 
slight increase in windward shower coverage can't be ruled out 
late Saturday night through the second half of the weekend as a 
weak trough passes to the south. A return of drier trade wind
conditions is expected early next week. 

&&

.DISCUSSION...
Guidance remains in good agreement heading into the weekend and 
depicts rising upper heights as the upper ridge noses westward
over the region and an upper low to the west moves out. Plenty of
middle- to upper-level dry air combined with a strong subsidence 
inversion and surface ridge anchored north of the area will 
support the stable trade wind pattern holding through the first 
half of the weekend. The northern periphery of an area of enhanced
low-level moisture associated with a weak trough passing to the 
south Sunday through Monday may translate to better windward and 
mauka showers - best chance over the Big Island. A return of 
drier trade wind conditions is shown early next week as the 
surface trough continues westward and further dampens. 

&&

.AVIATION...
With a nearly stationary high pressure center remaining far north
of the area, trade winds will persist in the moderate to breezy 
range through Thursday and beyond. VFR will prevail over most 
areas most of the time, but lower cloudiness and showers moving 
along with the trades will bring MVFR conditions to mainly 
windward and mauka sections from time to time. 

An AIRMET remains in effect for low level turbulence to the lee of
the mountains statewide. This will likely be extended through the
overnight hours.

&&

.MARINE...
A Small Craft Advisory (SCA) continues for windier waters around
Maui and the Big Island through tonight. Seas will near the SCA 
level threshold again Friday due to a combination of a north- 
northwest swell and trade wind waves.

A northwest swell which peaked earlier today will gradually ease 
tonight through Thursday. A larger north-northwest swell should 
begin to fill in Thursday night and peak Friday, with surf 
possibly near advisory levels along exposed north and west facing 
shores of the smaller islands. This swell will slowly fade into 
the weekend. Surf along south facing shores will remain elevated 
into the second half of the week as a long-period south swell 
moves through. This should peak around Thursday before fading 
into the weekend. Surf along east facing shores will remain small 
and choppy due to the fresh/strong trades locally and just 
upstream of the state.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big 
Island Southeast Waters.

&&

$$

DISCUSSION...Gibbs
AVIATION...Kinel
MARINE...Powell

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Western Regional Climate Center, wrcc@dri.edu