949 
FXHW60 PHFO 092001
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1001 AM HST Fri Oct 9 2020

.SYNOPSIS...
A surface trough near Kauai may bring some locally heavy showers
over leeward and northwest Kauai this afternoon. For rest of the
state, Light to moderate east to southeast trade winds will 
continue through tonight, then become more easterly late Saturday 
as the trough north of Kauai shifts west of the area. Although 
drier air and more stable conditions moving in will limit shower 
coverage across the islands into Sunday, a few windward and 
mountain showers will remain possible overnight through the 
morning periods. A modest increase in moisture associated with 
former tropical cyclone Marie moving through the state from east 
to west will support better shower coverage late Sunday through 
early next week.

&&

.DISCUSSION...
Latest satellite imagery is showing an upper level low located
about 350 miles north of Kauai. This upper level low along with
its associated surface trough will be the main weather concerns
for this afternoon. Early morning sounding from Lihue is showing
precipitable water values of 1.54 inches with a weak inversion at
4500 feet and unstable conditions aloft. Developing sea breezes
along with a weak short-wave trough should be enough for the
development of some brief heavy showers over parts of Kauai this 
afternoon. The most likely area would be over leeward Kauai and NW
Kauai. 

Over the rest of the state, we have light to moderate east-
southeast winds and a dry and stable airmass moving in from the 
east, which should limit shower activity. A few isolated showers 
will still remain possible, but rainfall amounts will be light. 
Over Oahu, the forecast remains uncertain due to the unstable 
airmass off to the west and stable airmass to the east. We will 
likely see some interior showers develop this afternoon, but the 
intensity of these showers remain uncertain. Any shower 
development this afternoon should quickly dissipate in the evening
as the sun sets.

For this weekend the light to moderate winds will persist, but 
the wind direction will shift more easterly as the surface trough 
NW of Kauai moves away from the state. Stable conditions with a 
dry airmass will produce fair weather on Saturday with some light 
isolated showers. A surface trough approaching the state from the
east could bring an increase of showers on Sunday into early next
week. This surface trough is the remnants of former tropical 
cyclone Marie, which will likely bring an increase of humidity as 
well. So overall starting Sunday and continuing through early next
week, we will likely begin to see more shower activity with light
to moderate easterly winds. Due to the lighter winds and higher 
humidity, the weather may feel warmer than usual.

&&

.AVIATION...
A weak ridge of high pressure northeast of the state will keep 
light to locally moderate, east-southeasterly trade winds in place
through tonight. The trades will be light enough, though, to allow
for sea breezes and land breezes to develop at many of the terminals
during the next 24 hours. Rather dry and predominantly VFR conditions
should prevail in most areas. However, a band of moisture and a 
possible weak disturbance moving through could lead to the development
of a few heavier showers over Kauai this afternoon. 

No AIRMETs are in effect, though AIRMET Sierra may be needed for 
mountain obscuration across Kauai this afternoon.



&&

.MARINE...
An eastward moving surface high currently located far north of 
the islands will maintain light to moderate trade winds into next
week. Surface troughing to the west of the state will veer trades
more southeast, especially west of Maui, this weekend. The 
associated upper low moving in the vicinity of the northwest far 
offshore waters will increase shower and thunderstorm probabilities
mainly northwest of the island. Trades may near Small Craft Advisory
(SCA) criteria through the smaller island bays and channels and 
across the Big Island's southern waters the next couple of days. 
On Sunday, areawide moderate trades will return as high pressure 
settles in northeast of the islands. The remnants of Tropical 
Cyclone Marie will cross the islands as a weak trough from the 
east Sunday and Monday. This trough passage will subtly waver 
trades from the northeast to southeast while increasing east-to-
west shower chances. A cold front approaches the state from the 
northwest at mid week that may back northern water winds from the 
northwest by this time next week.

The northwest swell will continue to slowly subside going into 
the weekend. Small, longer period northwest swells are expected 
to arrive tonight and then be reinforced by slightly larger, 
short period northwest swells Sunday. These reinforcing swells 
should be coming through during the week in maintaining near 
normal north-facing shore surf.

The south-facing shores will be facing a series of small, long 
period swells from the south-southwest today through early next 
week. These series of south swells will keep slightly below 
October average 2 to 4 foot fun surf alive along south-facing 
shores into next week.

The east swell from once Tropical Cyclone Marie will fade through
the day. Thus, surf along east-facing shores will be lowering 
from moderate to small through the weekend. Surf will likely 
remain relatively small through mid next week due to relatively 
weaker trade flow. 


&&

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

&&

$$


DISCUSSION...Kino
AVIATION...TS
MARINE...Blood