Drought in Hawaii, March 1 to 31, 2020

Area Forecast Discussion
National Weather Service Honolulu HI
833 PM HST Sat Feb 29 2020

.SYNOPSIS...
A strong high pressure system northeast of the state and an upper
level low over the islands will keep wet and windy trade winds
in the forecast through Monday morning. Expect brief heavy
passing showers across all islands with isolated thunderstorms
through the weekend in an unstable flow pattern. Weather
conditions will gradually improve with moderate to breezy trade
winds starting on Monday as the upper low weakens and lifts
northward and the high pressure center drifts eastward. Drier
weather conditions remain in the forecast from Tuesday through
Thursday. Winds and showers trend higher from Friday into next
weekend as another strong high builds in from the north.

&&

.DISCUSSION...
A strong 1040 MB surface high far to the northeast of the Hawaiian
Islands continues to produce windy trade winds across the state.
Sustained surface winds in the 20 to 35 MPH range with gusts
around 50 MPH are expected. The strongest wind gusts will occur in
passing heavy showers. A Wind Advisory remains in effect through
Monday morning for all areas except the highest summits of the Big
Island and Haleakala Maui where advisory criteria is higher.

A cold core upper level low has settled in over the eastern half
of the state this evening. This upper low will keep unstable
conditions with frequent showers heavy at times in the local
forecast through Monday morning. Thunderstorms are developing over
portions of Maui and the Big Island this evening, the potential
for isolated thunderstorms remains in the forecast through Sunday.
Strong winds aloft will keep these shower bands moving quickly
through each island at around 30 MPH. At these faster storm
motion speeds heavy rainfall will struggle to produce any
widespread flooding concerns. However, localized flooding is
still possible if heavy rainbands repeatedly develop and train in
over one location.

By Monday, forecast guidance suggests that the upper level low
will weaken and begin to drift northward away from the island
chain. The strong high pressure system far to the northeast of the
state will also weaken and drift eastward away from the islands.
The weakening of these pressure systems will decrease both the
trade wind speeds and shower activity statewide starting on
Monday.

Tuesday through Thursday...Expect lighter trade winds over the
islands in a drier isolated to scattered shower pattern through
the middle of next week.

Friday and Saturday...Another strong high pressure system will
build in far north of Hawaii producing breezy trade winds into the
weekend. A weak upper trough moving in from the north will also enhance
shower activity. This upper level trough is much weaker than the
current upper low center, therefore the shower coverage with this
next system will be lower as compared to this weekends activity.

&&

.AVIATION...
High pressure northeast of the state will keep strong and gusty
trade winds in place through Sunday. Numerous to widespread
showers will affect windward areas through the period, with
showers regularly reaching leeward areas as well. Cold air aloft
associate with an upper level low over the region will bring a
slight chance for thunderstorms overnight, particularly in
windward locales.

AIRMET Sierra remains in effect for mountain obscuration across
windward sections of Kauai, Oahu, Molokai, Maui, and the Big
Island. These conditions should persist through the night.

AIRMET Tango remains in effect for low level turbulence over and
downwind of the terrain of all islands. These conditions will
likely persist through the weekend. AIRMET Tango also remains in
effect for upper level turbulence over Kauai and Oahu. These
conditions will likely persist through the night.

&&

.MARINE...
Strong east-northeast trades associated with 1041 mb high
pressure northeast of the state will continue into the upcoming
week before trending down. Pailolo and Alenuihaha Channels,
Maalaea Bay and waters around South Point of the Big Island will
remain near gale-force levels through this time. WAVEWATCH III
and ECMWF-Wave guidance depict seas building into the 12-18 ft
range late tonight through Monday across a good sized area within
a couple of hundred nautical miles to the northeast of the
windward waters as the gradient tightens. The Small Craft Advisory
(SCA) remains in effect for all waters due to a combination of
winds and seas, which continues through Monday.

In addition to the rough conditions, showers and thunderstorms
associated with an upper low in the area will continue to impact the
island waters, especially the windward waters. Some of these showers
will be heavy and capable of producing strong winds and locally
higher seas. A surface trough is forecast to approach and move
through the waters from east to west early next week. There may be a
brief period of time when the local winds trend down into the light
to moderate range for some locations as this trough moves through.

Surf along east facing shores will steadily rise overnight through
Sunday due to the aforementioned scenario evolving over and upstream
of the islands. Heights will hold around the advisory level (8 ft)
tonight, then climb toward warning levels Sunday through Monday. If
seas climb to levels well above predicted, a warning will become a
possibility for east facing shores.

Surf along north and west facing shores will continue to lower
through Sunday as the northwest swell lowers. This will be the
beginning a quiet stretch for north and west facing shores, which
may continue through all of next week. Some of the trade wind
energy, however, may wrap into exposed north facing shores each day.

Surf along south facing shores will remain small with mainly
background southerly swells moving through.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 AM HST Monday for all islands except the
summits of Haleakala and the Big Island.

High Surf Advisory until 6 PM HST Monday for East facing shores of
Kauai Oahu Molokai Maui and the Big Island.

Winter Weather Advisory until 6 PM HST Sunday for Haleakala
Summit-Big Island Summits.

Small Craft Advisory until 6 PM HST Monday for all Hawaiian
waters.

&&

DISCUSSION...Bohlin
AVIATION...Jelsema
MARINE...Gibbs