Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/11/23

Area Forecast Discussion

National Weather Service Honolulu HI

 336 PM HST Sat Jun 10 2023

.SYNOPSIS...
High pressure north of the islands will keep moderate to breezy
trade winds in place through the middle of next week, with only
minor fluctuations in strength from day to day. Rather dry and
stable conditions will persist through Sunday with light showers
favoring windward and mauka areas. A disturbance aloft coinciding
with occasional increases in low-level moisture will bring wetter
trade wind weather to the state next week.

&&

.DISCUSSION...
This afternoon, a surface high is centered over 1300 miles
northeast of Honolulu with a ridge axis extending north of the
main Hawaiian Islands. As a result, locally breezy easterly wrap-
around trade wind flow is being observed across the state. The
afternoon 00z soundings at Hilo and Lihue show that the airmass
over the islands continues to be dry and stable with trade wind
inversions ranging from about 5,000 to 7,000 feet respectively.
Latest satellite and radar imagery depicts just a few light
showers moving into windward locations of Kauai and Oahu and just
upstream of the Big Island, while mostly sunny skies are observed
over the islands of Maui County. Typical afternoon cloud buildups
and a few light showers are also observed over leeward Big Island.
In the upper levels, water vapor imagery shows an upper trough
northwest of Kauai. Southerly flow aloft on the east side of this
trough is directing a few high clouds north of Kauai, but more
westerly upper level flow further east is allowing a band of thin
cirrus to pass over the eastern end of the state.

The high pressure far northeast of the island chain is expected to
strengthen slightly through the rest of the weekend and then remain
nearly stationary through at least the middle of next week. This
will keep moderate to locally breezy trades over the islands for
the next several days with only minor day-to-day fluctuations. The
dry and stable trade wind weather will continue through Sunday
with light showers favoring windward and mauka areas, mainly
during night and morning. Leeward areas will stay mostly dry,
except for the typical cloud and shower buildups over leeward Big
Island in the afternoon. Based on latest guidance and observations
from the previous couple of days, trended shower chances down for
some windward locations from what was previously forecast for
Sunday.

Models show the trough aloft northwest of the state will develop
into an upper low tonight and move southeastward near or over the
island chain by late Sunday. This will break down mid-level
ridging and the subsidence inversion. By Monday night into early
Tuesday, remnant moisture from an old frontal boundary will
approach the islands on the trade wind flow. With the enhanced
low-level moisture approaching as the low aloft settles near the
islands, trade wind showers could increase in both coverage and
intensity.

The trades may ease a bit late next week as the high to the
northeast weakens slightly, though they will still maintain
moderate speeds. Additional surges of increased low-level moisture
coinciding with the low aloft lingering nearby have the potential
to bring periods of wetter trade wind weather throughout the
remainder of next week.

&&

.AVIATION...
Vertical wind profiles from local radars only show 20-25kt of
wind at low levels. However, recent AMDAR soundings out of
OGG show 25-30 knots in the mixed layer below the inversion. This
setup continues to support low-level turbulence downwind of the
terrain. With breezy trades expected to continue, the current
AIRMET for moderate turbulence will likely remain in effect for
the next several days.

Conditions will be primarily VFR, with brief MVFR
ceilings/visibilities in showers. Showers will be greatest
across windward sections during the night and morning, and also
across leeward sections of the Big Island during the afternoon and
evening.

&&

.MARINE...
Moderate to locally strong easterly trades will continue through
the first half of next week as a surface ridge remains anchored
north of the islands. A Small Craft Advisory (SCA) is in effect
for the windier waters and channels from Molokai to the Big
Island. The SCA will likely be extended through next week, and
trade winds may increase slightly late Monday into Wednesday.
SCA`s may need to be expanded to other areas during this time. A
downward trend is possible late next week as the ridge settles
southward into the area.

An out of season west-northwest swell will gradually decline this
weekend and dissipate by early next week. Background swell from
the northeast will keep small surf along select north facing
shores through middle of next week. In the extended, Typhoon
Guchol will likely become extratropical in the northwest Pacific
during the middle of next week and may send a larger northwest
swell to Hawaii next weekend.

Surf along east facing shores will gradually build through early
next week with the fresh trades in place, especially Tuesday
through Wednesday as a short-period northeast groundswell mixes
in.

Surf along south facing shores will remain small each day as a
mix of long-period background south and southwest (170-220 degree)
swells move through.

&&

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

&&

$$

DISCUSSION...Vaughan
AVIATION...Bravender
MARINE...Kino