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Hawaiian Islands Synoptic Discussion and Guidance

120
FXHW60 PHFO 181342
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
342 AM HST Tue Jun 18 2024

.SYNOPSIS...
Surface high pressure north of the state will maintain breezy
trade winds through tonight, with trades strengthening into the
breezy to strong range Wednesday through the weekend. Fairly
typical windward and mauka-focused shower activity is expected
through much of the week. Remnants of an old frontal boundary
could increase windward shower activity late Friday into Saturday.

&&

.DISCUSSION...
A weak upper-level low, centered a couple hundred miles southeast
of Oahu, continues to sending high clouds northward across the
eastern half of the state this morning. Expecting a fairly typical
trade weather pattern through Tuesday night, with breezy wind speeds
and passing showers focused on the windward and mauka areas. Shower
activity will be slightly higher than usual, due to the upper low,
with some moderate showers possible over windward areas at times,
mainly during the overnight and early morning hours.

As the upper-level low gradually moves westward and weakens over
the next few days, we should see inversions lowering, with drier
conditions around mid-week. Beginning Wednesday into Thursday,
the surface high centered far north of the state will strengthen,
increasing the trade wind speeds into the breezy to strong range
during the second half of the week and into the weekend. The global
models are showing an area of enhanced moisture, associated with
an old frontal boundary, riding in on the trades toward the end of
this week. This could produce enhanced windward showers late Friday
into Saturday.

&&

.AVIATION...
Breezy trades will continue, with SHRA and low cigs favoring
windward and mauka locations. Periods of MVFR conds are possible
in any SHRA. Otherwise, VFR conds should prevail.

AIRMET Sierra is in effect for mtn obsc for windward portions of
all islands.

AIRMET Tango is in effect for mod turb between 140 and FL300 from
the Big Island up through Molokai.

&&

.MARINE...
Fresh to strong easterly trades will strengthen later today
through the second half of the week as the surface ridge builds
north of the state. This has resulted in the Small Craft Advisory
expanding up the island chain from the typically windier waters
around Maui County and the Big Island. Additional marine zones may
need to be added in later packages. Seas will quickly respond and
build to the advisory level across the Alenuihaha Channel and
waters near South Point beginning around Wednesday.

Surf along south-facing shores continues to ease this morning,
and that trend will persist today. Expect mainly background south
to south-southwest pulses moving through until Friday. A slight
upward trend is possible by the end of the weekend from a small,
long-period south swell. Guidance shows this arriving Saturday
night into Sunday, then lingering into early next week.

Surf along east-facing shores will hold around average today,
then gradually trend up through the second half of the week due to
the aforementioned trades strengthening locally and upstream of
the islands over the eastern Pacific.

Surf along north-facing shores will return to the typical
summertime (flat) levels later today through midweek as a small
northwest swell moves out. As the trades increase, some northern
exposures could see a gradual increase later this week.

&&

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

&&

$$

DISCUSSION...TS
AVIATION...SMW
MARINE...Gibbs

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office