Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 171314
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
314 AM HST Sun Mar 17 2024

.SYNOPSIS...
Moderate northeast trades will shift out of the east later today
through Monday, then continue through the first half of the week.
Despite the drying trend from west to east, some residual moisture
lingering over the eastern end of the state from a recent front
will support mostly cloudy skies, along with a few showers
persisting this morning over windward areas. Otherwise, mostly
dry and stable conditions are anticipated through the first half
of the week, with the best rainfall chances favoring windward and
mauka areas overnight. A return of breezy easterly trades and
increasing rainfall chances is possible through the second half of
the week as an upper disturbance moves into the area.

&&

.DISCUSSION...
Satellite imagery shows an area of low-level moisture and clouds
lingering across the eastern end of the state from a frontal
boundary that recently passed through. The early morning upper air
sounding reflected this and showed a moist profile up to the
trade wind inversion near 7 kft. Showery conditions have resulted
this morning over windward and mauka locations of the Big Island,
where accumulations have reached around a quarter of an inch over
the past 6-12 Hrs. Expect this trend to continue through a good
portion of the day before drier air spreads into the area and the
clouds begin to scatter. Elsewhere, outside of a few morning
windward showers, expect mostly dry and stable conditions today
with moderate northeast trades.

Guidance remains in good agreement, indicating dry and stable
conditions continuing through the first half of the week as upper
heights rise over the region and the aforementioned moisture near
the Big Island dissipates. This will create a more suppressed
environment with precipitable water values remaining around an
inch or less. Trades will shift out of the east beginning later
tonight and maintain moderate levels. The best chances for a few
showers will be over typical windward and mauka locations
overnight through the early mornings. Any leeward showers are more
likely to occur in the afternoons, where localized sea breezes
form.

A gradual strengthening and destabilization of the trade wind
flow is possible Wednesday into Friday. There is higher confidence
that trades will likely increase as a deeper surface high sets up
far north of the state, potentially resulting in breezy
conditions by Friday. An upper-level trough will slowly pass over
the region during this time, bringing 500 mb temperatures as low
as -16C on Wednesday night and Thursday. While there could be
some increase in shower coverage in response to the added
instability, a mid-level ridge may be able to maintain stability
and lower the chances of heavy rainfall.

&&

.AVIATION...
Light to moderate trade winds will rebuild over the state today.
Bands of clouds and light showers off the Pacific will favor north
and northeast facing slopes and coast. Late night soundings
reveal plenty of low-level moisture persisting over the far
eastern end of the state, and strong stability statewide. AIRMET
Sierra for mountain obscuration for northeast facing slopes of the
Big Island is thus expected to remain necessary through midday
and possibly beyond. VFR cloudiness will prevail elsewhere across
the state.

&&

.MARINE...
Weak high pressure will drift north of the state the next few
days. This will result in moderate to locally fresh east trade
winds through the middle of the week. A new high settling in from
the north late in the week will tighten the regional pressure
gradient enough to produce fresh to locally strong trades.

The current near 5 foot, medium period northwest (300-320 degree)
swell will continue to slowly fall through Tuesday. The far
northwest buoys are sensing a reinforcing moderate size, longer
period northwest (320-330 degree) swell this morning. This swell
should be enough to push today`s already slightly elevated surf up
a notch to near High Surf Advisory (HSA) levels along many better
exposed north and west-facing shores through Monday afternoon.
The arrival of a significant moderate size, long period northwest
(310-330 degree) swell late Tuesday and Wednesday will likely
produce solid mid week advisory level surf with a late week
decline to below HSA heights Thursday. A slight boost to south
surf is expected from today through Tuesday as a small, long
period south (200 degree) swell moves around the islands through
Tuesday. East shore surf will remain small through early next week
with a slight pick up in chop anticipated later in the week with
strengthened trades.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&
$$

DISCUSSION...Gibbs
AVIATION...Bedal
MARINE...Blood


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