Drought in Hawaii, November 1 to 30, 2022

Area Forecast Discussion
National Weather Service Honolulu HI
833 PM HST Mon Oct 31 2022

.SYNOPSIS...
Moderate to locally strong trade winds will focus clouds and
showers over the windward and mauka areas for another day or two,
with showers being more prevalent over the Big Island. Trades are
expected to weaken some later Tuesday, before building again
during the second half of the week. A passing trough will bring an
increase in shower activity during the second half of the week.

&&

.DISCUSSION...
A high pressure system centered far north of the state will
maintain a trade wind pattern through the week. Meanwhile the
upper level low to the far northeast of the islands continues to
have an impact on the local weather. A brief thunderstorm over the
Big Island today was due in part to the instability left over the
southern part of the state. Additional towering cumulus have been
noted just outside the coastal waters. A surface trough associated
with the upper level low is expected to move to the west over the
next couple days. Initially this is helping to tighten the
pressure gradient over the islands, but as we head into midweek,
it will help to weaken the trades a bit.

The afternoon sounding from Hilo was saturated due to the showers
on the windward side of the island, but also showed no inversion
over the island. The global models suggest not a lot of change in
the inversion, or lack thereof, for Tuesday afternoon. The high
resolution models show PoPs remaining elevated for the Big Island,
with the HREF indicating some heavier showers will remain
possible. All the pieces aren't lining up in one place, so feel
the current forecast is sufficient for the time being. If
anything will boost PoPs for tomorrow over the Big Island for the
morning package.

The smaller islands appear to be more in a typical trade wind
pattern regime. The afternoon sounding from Lihue had precipitable
water (PW) near 1.28 inches which is within normal values for
November. Satellite derived PW show some drier air upstream of the
smaller islands, which will likely mean lower rainfall totals for
those islands through Tuesday.

As the above mentioned trough moves closer to the islands Tuesday
night, we will likely see an increase in shower activity.
Initially the clouds and showers will remain focused over the
windward sides of the islands. As the winds increase later
Wednesday, some of the clouds and showers will be carried to
leeward areas.

&&

.AVIATION...
A steady stream of moisture aimed at Windward Big Island will
maintain MVFR to (locally) IFR conditions within low clouds and
steady showers there for at least the next few hours. Satellite
imagery suggests that that the land breeze has nearly pushed
offshore potentially leading to improving conditions at PHTO.
However, the onshore concerted push of low-level moisture will
continue for several more hours and will likely be strong enough
to overcome the land breeze at times. The forecast for MVFR/tempo
IFR to continue at Hilo through about 14z/4am HST therefore
carries greater-than-normal uncertainty.

Elsewhere, locally breezy trades will focus occasional showers
and low clouds over windward and mauka zones with nothing more
than localized MVFR expected.

AIRMET Sierra for mountain obscuration over Windward Big Island
remains in effect.

AIRMET Tango for lee turbulence remains in effect.

&&

.MARINE...
A high pressure system far north of the Hawaiian Islands continues
to produce moderate to locally strong trade winds over the region.
A Small Craft Advisory (SCA) remains in effect for windier waters
around Maui and the Big Island. Wind speeds may briefly drop
below SCA thresholds from late Tuesday into Wednesday, due to a
passing surface trough, however winds will ramp back up into the
SCA range quickly from late Wednesday onward as the surface trough
fades.

Small surf will continue for all islands into the weekend. East
facing shores will see increasing surf height trends by the end of
the week as trade wind speeds increase from Thursday onward.
North facing shores will see small north to northwest swells
keeping small to fun size surf in the forecast through Saturday.
South facing shores will see a few long period south swells
moving up from the South Pacific, keeping surf heights elevated
through the week. West facing shores will see small northwest and
south swell wave wrap.

&&

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

&&

DISCUSSION...M Ballard
AVIATION...JVC
MARINE...Bohlin