Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 300128
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
328 PM HST FRI JUL 29 2016

.SYNOPSIS...
A surface high to the north will keep trade winds blowing over the
islands through the coming week. The trades will carry areas of
tropical moisture over the islands while a passing low aloft will
make the atmosphere more unstable over the next several days.
This combination will keep the weather rainier than normal over
much of the next week.

&&

.DISCUSSION...
A 1034 MB surface high 1600 miles north northeast of Honolulu at
42N148W will move slightly to the west with little change in
strength through tomorrow. The pressure gradient southwest of the
high will keep breezy trade winds blowing over the main Hawaiian
Islands tonight. Balloon soundings at 200 PM showed a temperature
inversion over the state from 6000 feet at Lihue to 8500 feet at
Hilo. This inversion will limit cloud growth and keep rainfall
light late this afternoon.

However, this will begin to change this evening as the water
vapor satellite imagery shows a low aloft 730 miles east
northeast of Honolulu at 26N148W moving toward the west northwest
around 15 mph. As this low moves by the islands tonight through
early next week, it will weaken the trade winds and raise the
temperature inversions. There is evidence of this already on the
Hilo sounding with the higher inversion height. The higher the
inversions mean that the trade wind showers will become more
active. Radar shows the shower intensity has boosted somewhat
since this afternoon, and we should continue to see the increasing
trend tonight. Most of the rain focused over the typical windward
and mauka areas, but leeward areas will also see occasional
passing showers over the next few days.

Next Tuesday, the low aloft moves north away from the islands and
the trade winds will become breezy again through the remainder of
the week. A drier airmass will carry in with the trades about that
time, so less showers are expected on Tuesday into the Wednesday
afternoon. Showers will increase again Wednesday night as another
plume of moisture moves in with the trade winds.


&&

.AVIATION...
AIRMET TANGO for low level turb over and S through W of the
mountains remains posted as breezy NE to E trade winds continue.
The 00Z soundings from PHTO and PHLI show strong inversion
between 5 and 8 thousand feet.

Expect primarily VFR conditions with isolated MVFR conditions
along the windward slopes and over windward waters as trades
bring in low clouds and showers from the east.



&&

.MARINE...
A high to the northeast will maintain fresh to locally strong trade
winds across the area tonight. A Small Craft Advisory (SCA) is in
effect for the typical windy zones around Maui County and the Big
Island tonight. Winds will taper off as a weak surface trough
arrives from the east tonight into Saturday. Some or all zones may
drop out of the SCA this weekend. The trade winds will strengthen
again by the middle of next week.

The trade winds will produce choppy surf along east facing shores
during the breezy time periods as mentioned earlier, but surf is
expected to remain below advisory levels over the next week.
There will be a series of small south swells into next week but
surf will remain below the advisory level along south facing
shores. Only small surf is expected along north and west facing
shores.


&&

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


&&

$$

DISCUSSION/MARINE...Foster
AVIATION...Morrison



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