Area Forecast Discussion
Issued by NWS Honolulu, HI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
000
FXHW60 PHFO 271349
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
349 AM HST Fri Jan 27 2023

.SYNOPSIS...
Cool, dry and breezy northeast trade winds will continue over
Kauai and Oahu through early Saturday, as cloudy and locally wet
conditions persist near a dissipating front over the Big Island
and Maui County. A trough, remnants of the front, will linger
over the island chain during the weekend and possibly Monday,
bringing strong northeast trade winds to Kauai and Oahu. A
disturbance aloft will increase the potential for locally heavy
rainfall late Saturday and Sunday.

&&

.DISCUSSION...
A stalled front is focusing showers across windward slopes of
northern Big Island and Maui County, while cool, dry, and stable
conditions persist over Oahu and Kauai. Meanwhile, a sharp upper
level trough is generating thick layered clouds across the Big
Island and Maui and is maintaining enough instability to trigger a
few thunderstorms along the front on northern Big Island. The
heaviest showers have been occurring in remote portions of the
Kohala mountains, and numerous gages on the Hamakua Coast, North
Kohala District and windward Maui have measured over a half inch
of rainfall during the past six hours, while the West Wailuaiki
station has picked up over two inches. In a sharp contrast, the
breezy northeasterly flow in place across Oahu and Kauai has
produced no rainfall, and dew points in the mid to upper 50s are
maintaining a cool feel.

Expect little change through tonight as the front weakens to a
surface trough and the upper level trough broadens and slowly
weakens. The focus for rainfall should remain along the surface
trough, maintaining higher rain chances and the possibility of
thunderstorms along windward slopes of northern Big Island and
Maui County. Interior sections of the Big Island may experience an
afternoon heavy shower or thunderstorm, though high clouds
blanketing the eastern half of the island chain may inhibit
convection. In addition, the high summits of the Big Island could
see snow showers, mainly in the afternoon. On Oahu and Kauai,
expect morning windward clouds to deliver no rainfall and to
largely burn off by mid morning. Dew points may creep up as the
air modifies tonight, but chances for showers will remain very
low.

For Saturday, the surface trough will drift westward as upper
level trough begins to deepen west of the state. Wet conditions
will hold across windward Maui County and should shift back to
windward Oahu. The deepening upper level trough will generate more
widespread high clouds and may trigger a few thunderstorms across
the wetter windward areas. Interior Big Island could also see a
few afternoon thunderstorms and summit snow showers as well. Over
on Kauai, drier conditions will persist.

Saturday night into Monday, chances for heavy rainfall and
thunderstorms increase, but the details remain uncertain. The GFS
and ECMWF model both sharpen the upper level trough just west of
Kauai Saturday night and produce a compact upper level low to the
southwest of the state Sunday. This will lead to mid level ascent
that will thicken high clouds over the island chain and produce
moist and unstable conditions. The GFS continues to produce what
appears to be a spurious surface low over the state, and the more
believable ECMWF solution draws ample moisture over the Big
Island, while the lingering surface trough continues to feed low
level moisture over windward slopes of Maui County and Oahu, and
perhaps to Kauai be late Sunday. Due to ongoing model
inconsistencies, confidence is not sufficiently high for the
issuance of any flood related headlines at this time. There is
increased confidence that the sharpening low level trough will
lead to strengthening northeasterly trade winds over Kauai and
Oahu on Sunday.

Though wet conditions will likely linger into Monday, the GFS and
ECMWF show the upper level low drifting away from the state to
the southwest, suggesting that chances for heavy rainfall will
decrease as high clouds thin. Breezy east to northeast winds will
persist, focusing the bulk of the shower activity over windward
areas.

Beyond Monday, the forecast favors trade winds, but the
uncertainty remains unusually high regarding rainfall. The
longwave pattern points toward lingering upper level troughing,
suggesting that we could see another day or two of active showers.

&&

.AVIATION...
Dry and stable conditions, with limited showers, will persist
across Kauai and Oahu through today. Increased moisture and
instability east of Oahu associated with a stalled front will
continue to generate low clouds and showers, especially across
windward slopes of Maui county and the Big Island. Expect MVFR
conditions in low clouds and showers, with potential IFR
conditions as well. AIRMET Sierra is in effect for this and will
be updated as conditions warrant.

Models and a lack of reports show that earlier turbulence has
eased, allowing expiration of AIRMET Tango. Neither AIRMETS Tango
nor Zulu, for icing, are expected through today.

&&

.MARINE...
A front over the southeast waters will linger over the eastern
part of the state as it becomes a trough later today. This
feature will continue to produce periods of showers and isolated
thunderstorms around Maui County and the Big Island. Moderate to
locally strong northeast winds will strengthen today as a high
builds northwest of the state. Over the weekend a stronger high
will build northwest of the state, and a trough over or near the
state will sharpen the gradient, strengthening northeast trades to
strong to near gale speeds over the western half of the state by
Sunday. A Small Craft Advisory (SCA) is currently in effect due to
the combination of high seas and locally strong winds for most
zones through today. The SCA will need to be readjusted as seas
drop below 10 feet throughout the day.

As the current (310-320 degree) northwest swell fades, a series
of moderate north swells will move through today into the first
half of next week. These north swells will keep surf elevated,
especially along north facing shores. A new long period moderate
northwest swell (310 degree) is expected to boost surf heights
back to High Surf Advisory levels along north and west facing
shores Sunday into Monday. Surf along east facing shores should
see wrap from the north to northwest swells through early next
week. Elsewhere, small surf remains in the forecast for south
facing shores into early next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Friday for north facing shores
of Niihau, Kauai, Oahu, Molokai, and Maui.

Small Craft Advisory until 6 PM HST this evening 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-
Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters.

&&

$$

DISCUSSION...Wroe
AVIATION...Powell
MARINE...Shigesato


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.