National Weather Service Raw Text Product

953 
FXHW60 PHFO 061349
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
349 AM HST Tue Aug 6 2019

.SYNOPSIS...
Wet and humid conditions are anticipated across the state through 
midweek due to a combination of light winds and deep tropical 
moisture pooling northward in the wake of Post-Tropical Cyclone 
Flossie passing to the north. In addition to the wet pattern, a few 
thunderstorms will remain possible due to an upper trough over the 
region. Later in the week and into the upcoming weekend, a return of 
a more stable and drier pattern is expected with light to 
moderate trade winds.

&&

.DISCUSSION...
Recent satellite imagery showed the remnant low associated with 
Flossie beginning to lift northward away from the islands and a 
trailing plume of deep tropical moisture extending southward 
around the Big Island. Satellite-derived precipitable water (PW) 
imagery reflects this and depicts a large area of near to above 2 
inches over the state. Most of the overnight shower coverage has 
focused over the southeast slopes of the Big Island where 
accumulations have ranged from a quarter to a little over half of 
an inch in the past six hours (through 2 AM HST). Elsewhere, 
mostly quiet conditions have been in place due to the early 
morning land breeze. 

The short-term guidance remains in good agreement and keeps the 
wet and humid pattern in place through midweek. As Flossie lifts 
north and tracks away from the area, the aforementioned trailing 
plume of moisture will setup over the eastern end of the state
this morning, then over the central islands later today through 
Wednesday. Winds will remain light and variable, which will allow
for a land and sea breeze regime to become established. Dewpoints
will hover in the low to mid 70s. A combination of this moisture 
pooling northward over the state trailing Flossie and an upper 
trough positioned west of Kauai will keep the threat for heavy 
rainfall and flash flooding in the forecast. Although the 
potential for heavy showers will continue each day through 
Wednesday, the best coverage of heavy showers will favor interior 
sections of the islands through the afternoon and evening periods 
due to the sea breeze and light south-southeast low-level 
background flow. Additionally, a few thunderstorms can't be ruled 
out today due to the proximity of the upper trough and added 
instability. 

Later this week and into the upcoming weekend, guidance remains in 
decent agreement and depicts a return of a drier and more stable 
pattern as upper heights rise over the region. Trades are forecast 
to return, but could remain in the light to moderate category due to 
a weakness in the subtropical ridge north-northwest of the 
islands. Showers will favor windward areas, except where sea 
breezes setup over the interior and leeward locations through the 
afternoon and evening periods. 

&&

.AVIATION...
Light and variable winds will ensue for the remainder of this morning
as the remnants of Flossie pass just to the north of the Islands.
This light flow regime will lead to modified sea breeze 
development this afternoon with showers and isolated thunderstorms
forming over the islands interiors. Expect MVFR conditions at 
times due lowered visibility and mountain obscuration from thick 
low clouds and showers.

No AIRMETs are currently in effect.

&&

.MARINE..
As the remnants of Flossie track northward through the day, winds
are expected to shift to the southeast over the Big Island and 
Maui County waters while weakening and shifting northerly over the
western end of the state. High pressure will then build northeast
of the state, allowing moderate to fresh east trades to return 
from east to west across the islands Wednesday through Thursday.

The latest observations from the PacIOOS buoy at Hilo seas around
6 to 7 feet and will continue to lower through the day, so the
Small Craft Advisory has been dropped for all remaining waters.

Surf height and near-shore buoy observations are still elevated
enough along east facing shores of the islands this morning, so
will let the High Surf Advisory (HSA) continue through this
afternoon for all east facing shores. Will continue to monitor in
case the HSA can be dropped sooner as the swell eases through the 
day. Surf along south facing shores will rise through the second 
half of the week as overlapping south-southwest swells move 
through. 

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through this afternoon for Maui-Big Island.

High Surf Advisory until 6 PM HST this evening for Kauai 
Windward-Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-
Windward Haleakala-South Big Island-Big Island North and East.

&&

$$

DISCUSSION...Gibbs
AVIATION...Thomas
MARINE...Stall