Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 07/28/19

Area Forecast Discussion

National Weather Service Honolulu HI

 340 PM HST Sat Jul 27 2019

.SYNOPSIS...
Moderate to locally breezy trade winds will persist through at
least Wednesday, with an increase in trades expected by Thursday.
Stable conditions will hold through Sunday. Modest showers will
favor windward areas of all islands along with spotty afternoon
and evening showers over leeward slopes of the Big Island. A
slight increase in shower activity is possible early next week as
an upper level trough develops nearby. A tropical system will
pass near the islands late next week.

&&

.DISCUSSION...
Moderate to locally breezy trade winds and a rather typical
summertime rainfall pattern remain in place. Persistent surface
high pressure far north of the state continues to drive the trade
winds. A mid level ridge overhead is maintaining stable
conditions, and afternoon soundings and recent aircraft data
showed an inversion between 6,000 and 8,000 feet. Overall,
precipitable water (PW) is near seasonal normal (1.3 to 1.4
inches), though a small pocket of of enhanced PW up to 1.75 is
brushing the western end of the island chain. This feature
produced a short period of windward showers on Oahu this afternoon
and will quickly pass over Kauai during the next couple of hours.
Elsewhere, windward rainfall has been scant today, and leeward
areas have been mostly dry, with the exception of the South Kona
slopes of the Big Island where afternoon showers have flared up
again.

Expect little change through Sunday. Modest showers will favor
windward areas of all islands, and leeward Big Island slopes will
continue to experience spotty showers in the afternoon and
evening.

An slight uptick in shower activity is possible starting Monday,
while trades hold near current strength. An upper level trough
will develop just north of the state on Monday and settle nearby
through much of the week. As a result, the inversion will be
eroded and lifted. In this environment, showers moving along the
trade wind flow will be able to spread to leeward areas with
greater frequency. Since no organized areas of deep moisture are
noted in the GFS and ECMWF models, significant rainfall is not
expected.

The National Hurricane Center is issuing advisories on Tropical
Storm Erick, which currently sits about 2,000 miles east-
southeast of the state. The official forecast puts this system on
track to be near the islands late Thursday or Friday, but it is
too early to pin down any impacts with confidence.

&&

.AVIATION...
High pressure ridging remains anchored north of the state. This
feature is generating moderate to breezy trade winds across the
area. Low clouds and showers moving on the trades will mainly
affect windward facing coastal and mauka sections on all the
isles tonight, bringing isolated MVFR conditions and brief
mountain obscurations. However, VFR conditions are expected to
prevail.

AIRMET Tango remains in effect for areas below 8000 feet S thru W
of all mountains due to tempo moderate turbulence.

&&

.MARINE...
A high far north of the state will maintain fresh to locally
strong trade winds across local waters through Sunday, then
slightly decrease during the first half of the upcoming week as a
upper level trough moves over the area. A Small Craft Advisory
(SCA) remains in effect through Sunday for the typical windy
areas around Maui and the Big Island. As the upper trough moves
over the area Sunday night, pressure gradients are expected to
relax some and should result in a slight decrease of wind speeds
through the first half of the upcoming week. Wind speeds are
expected to drop to fresh speeds across the area but will still
hold near SCA speeds for the windy areas around Maui and the Big
Island through Tuesday. The current forecast shows winds dropping
below SCA speeds, but that may need to be adjusted depending on
the strength of the upper trough.

Choppy surf will continue along east facing shores each day due
to the breezy trades. Surf may increase towards the later half of
next week depending on the development of Tropical Storm Erick,
currently located in the eastern Pacific and tracking towards the
west at around 15 kt.

A combination of small southwest and southeast swells will continue
to provide small surf along south facing shores through the
weekend, remaining well below advisory levels. Surf is expected to
drop to background levels during the first half of next week. See
the Collaborative Nearshore Swell and Wind Forecast, SRDHFO, for
additional details on swell sources.

&&

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

&&

$$

DISCUSSION...Wroe
AVIATION...Foster
MARINE...Kino