Drought in Hawaii, August 1 to 3, 2021

Area Forecast Discussion
National Weather Service Honolulu HI
830 PM HST Sat Jul 31 2021

.SYNOPSIS...
locally strong and gusty trade winds along with stable and rather
dry conditions will persist during the next couple of days. Winds
will ease midweek as the high pressure far northeast of the state
weakens. Rather dry conditions will prevail into Tuesday with an
uptick in mainly windward showers expected midweek.

&&

.DISCUSSION...
A rather dry, stable, and gusty trade wind flow remains in place.
A 1030 mb high parked nearly 1500 miles north of the state is
driving the trades, and a ridge aloft overhead is producing very
stable conditions with a strong inversion based between 3500 to
6500 feet. As a result, scant rainfall was observed on windward
slopes today, and aside from typical afternoon showers on the
South Kona slopes, leeward areas have been very dry, including
sections of interior and leeward Big Island where a large wildfire
is burning.

Trades will increase slightly on Sunday as high pressure to the
northeast strengthens, and a firm ridge overhead will maintain
stable conditions with limited rainfall. Due to the expected
increase in trade winds, a Wind Advisory has been issued for
portions of Maui, Lanai, and the Big Island, including the area
where the large wildfire is burning. Another dry day is in store
with meager windward rainfall and sunny skies over most leeward
areas. Trades will gradually ease Monday and Tuesday as the high
to the northeast weakens, though dry and stable conditions will
likely hold.

Typical summer trade wind weather is expected by Wednesday. High
pressure will remain to the north of the state, but trades will
drop into the moderate to locally breezy range. A weakness in the
ridge aloft should allow the inversion to raise slightly, and the
GFS and ECMWF are hinting at an increase in low level moisture
that would translate into more windward showers.

&&

.AVIATION...
Stable conditions will support prevailing VFR through the forecast
period. Locally strong trades will focus occasional light showers over
windward slopes, mainly overnight, but any MVFR due to clouds or
shower activity will be fleeting. Low-level wind shear
characteristic of strong trades will be possible in favored
locations, namely around Maui and particularly in the vicinity of
PHOG. Finally, areas of low visibility can be expected over
sections of Leeward Big Island and adjacent waters due to wildfire
smoke.

AIRMET Tango for lee turbulence below 8kft will remain in effect
through the period.

&&

.MARINE...
Surface high pressure building far north-northeast of the state
will produce strong trade winds and elevated, rough seas through
Sunday afternoon. A Small Craft Advisory (SCA) remains in effect
for all Hawaiian waters through early Sunday morning. A Gale
Warning has been issued for the typically windier water adjacent
to the islands of Maui County and the Big Island Sunday. The SCA
will remain in effect for all remaining waters during the day on
Sunday. The latest forecast shows the trade winds weakening
slightly by Sunday evening, but SCA conditions will likely
persist over some waters through Sunday night. Expect locally
strong trade winds early next week, so the SCA will likely remain
in effect for the typically windier waters again from Monday
through mid-week.

Recent observations from the nearshore buoys at Pauwela and
Kaneohe Bay show wave heights of 6 to 7 feet with wave periods of
7 to 8 seconds, which likely reflects the strengthening trade
winds. Expect the rough surf to increase along east facing shores
through Monday. Surf heights may decrease to near the summertime
average along east facing shores by the middle of next week.

Small south and south-southeast swells are maintaining small surf
along south facing shores this weekend. By early next week, there
will mainly be residual south-southeast swell energy keeping
below normal summertime surf along south facing shores. A new
small southwest swell is possible towards the end of next week,
which may provide a small boost in surf heights along exposed
south facing shores.

The nearshore buoys at Hanalei and Barbers Point continue to show
tiny west-northwest swell energy, which was generated by recent
west Pacific tropical cyclone activity. This may produce a slight
bump in surf along exposed west facing shores of Kauai, and
possibly Oahu, through Sunday. Otherwise, expect nearly flat
conditions along most north and west facing shores through next
week.

&&

.FIRE WEATHER...
Near critical fire weather conditions will persist into Monday
due to strong and gusty trade winds and a rather dry and stable
atmosphere. The Keetch Byram Drought Index at Honolulu stands at
591, just shy of the critical 600 mark, but winds and daytime
relative humidity will be at or very close to critical thresholds
on Sunday. A slight drop in winds is expected on Monday and
Tuesday, but dry leeward conditions will hold.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 6 AM to 6 PM HST Sunday for Lanai Mauka-Maui
Leeward West-Kohala-Big Island Interior-Lanai Windward-Lanai
Leeward-Maui Central Valley North-Maui Central Valley South-Big
Island South-Big Island Southeast.

Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

Gale Warning from 6 AM to 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Big Island
Windward Waters.

&&

DISCUSSION AND FIRE WEATHER...Wroe
AVIATION...JVC
MARINE...Houston