026 
FXHW60 PHFO 310155
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
355 PM HST Wed Oct 30 2019

.SYNOPSIS...
Daytime sea breezes and nighttime land breezes will continue
through the weekend. An upper trough passing north of the islands
will bring the potential for some heavier showers and 
thunderstorms into this evening and possibly again tomorrow 
afternoon. Drier and more stable conditions are expected Friday 
through the weekend. A weak cold front will reach Kauai Sunday 
into Monday and dissipate.

&&

.DISCUSSION...
Water vapor imagery shows an upper low 100 miles north of Honolulu 
moving towards the east southeast at 20 mph. The upper trough is 
inducing an area of low pressure at the surface around the islands
which is keeping the background wind flow light and variable this
afternoon. Visible satellite and radar show partly sunny skies 
over the islands this afternoon with scattered showers impacting
all of the islands to some extent. Some of the showers have been
heavy with accumulations near 3 inches on Kauai and 1 inch on 
Oahu since noon over the windward sections of both islands. The 
instability provided by the low and moisture available will keep 
the possibility of heavy showers and thunderstorms through early 
evening. Land breezes will clear out the islands later tonight 
with sunny conditions expected in the morning.

As the low tracks east tonight, a second upper low will form on 
the backside of the departing low and move over the western end of
the state before tracking eastward through the day Thursday. This
could destabilize the atmosphere enough to bring another round of
heavy showers and a slight chance of thunderstorms mainly during 
the afternoon and evening hours in conjunction with the sea 
breeze. Thursday's chance for heavy rain/thunderstorms will be a 
bit more limited as the much of the moisture over us today is 
expected to move east into a more organized convergence band that
is not expected to impact the state.

Friday and Saturday, the potential for heavy showers is expected 
to diminish as an upper level ridging builds in. Background winds
will remain gentle, but begin to push out of the southwest as a 
weak cold front approaches from the northwest. Daytime sea breezes
and nighttime land breezes will continue to dominate resulting in
afternoon clouds and spotty showers followed by clearing at 
night. The front is expected to stall near Kauai Sunday night  
and dissipate Monday. A longwave trough will approach the islands
towards the middle of next week build another surface trough over
the area. Hard to say this far out how much impact will be felt 
across Hawaii, but it doesn't bode well for a return of the trade
winds.


&&

.AVIATION...
A low pressure system continues to reside north of the state this
afternoon. This feature should help maintain the chance of 
scattered SHRA/+SHRA well into the evening. MVFR ceilings and 
visibility will occur where the heavier showers pass over, 
generally on the windward sides of the islands. By tonight, with 
the loss of diurnal heating, precipitation and cloud cover are 
expected decrease in coverage.

A sea breeze/land breeze regime will exist across the area 
tonight and again on Thursday with a light flow pattern in place.

No AIRMETs are currently in effect. 


&&

.MARINE...
An area of low pressure will linger north of the islands during 
the next couple of days, leading to gentle variable winds over 
coastal waters and periods of thunderstorms. For the most part, 
thunderstorms have been passing just north of the coastal waters 
today, though we could see a few flare near the islands into early
evening and again on Thursday afternoon as an upper level 
disturbance passes overhead. The area of low pressure will lift 
north of the offshore waters by Friday, eliminating the threat of 
thunderstorms and keeping winds across the region rather weak. 
Gentle to locally moderate south to southwest winds will develop 
late Friday and Saturday as a front approaches. The weakening 
front may reach Kauai on Sunday. 

The current north-northwest swell continues to be slow to decline
and elevated a couple feet above Wavewatch guidance. The Waimea 
Bay and Pauwela PacIOOS buoys have been measuring the swell around
7 to 8 ft at 13 to 14 seconds this afternoon, which again 
warrants the extension of the High Surf Advisory (HSA) for north 
facing shores from Kauai to Maui through tonight. With the swell 
shifting out of the north-northwest, surf has dropped along west 
facing shores, where the HSA has been cancelled. In addition, the
Small Craft Advisory for hazardous seas has been dropped. The 
northwest swell will continue to slowly subside tonight into 
Saturday, and a HSA will likely be needed again Sunday night and 
Monday as a another northwest swell passes through. 

Modest increases in surf are due along east and south facing 
shores over the next few days. A small short-period northeast 
swell will persist into Friday, though surf will remain below the 
advisory level. A small bump out of the south-southwest is 
expected into the weekend along south facing shores.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Thursday for north facing 
shores of Niihau, Kauai, Oahu, Molokai and Maui.


&&

$$


DISCUSSION...Foster
AVIATION...Thomas
MARINE...Wroe