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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 051348
Area Forecast Discussion
National Weather Service Honolulu HI
348 AM HST Tue Jul 5 2022
Locally strong trades will remain wetter than normal through
tonight, particularly for the windward slopes of Maui County and
Oahu. Trades and shower coverage then trend downward during the
latter half of the week.
Locally strong trades around the southern periphery of surface
high pressure is directing a remnant band of frontal moisture
over the central portions of the state this morning. Local radar
imagery reveals frequent showers traversing windward and mauka
slopes of Maui County and Oahu with lighter showers frequently
drifting leeward, especially over Oahu. The primary adjustment to
the forecast for today was to adjust pops and sky cover upward in
these areas for the remainder of the morning. Decreased shower
coverage is noted over Windward Kauai along the northern fringe of
this band. The same can be said for the Big Island where the land
breeze has cleared downslope areas of clouds and showers for the
time being. The morning soundings out of Hilo and Lihue confirm
the arrival of the well- advertised band of mid-level dry air
around centered around 700mb. The presence of this drier air aloft
will ensure continued stability and will limit rainfall amounts
away from the most favored locales even as shower coverage remains
high. The diurnal heating will bring some improvement by this
afternoon, causing showers to trend downward until this evening.
Showers then increase in coverage over roughly the same areas
The mid-week period will be characterized by slight weakening of
trades as the expansive high that has dominated the circulation
over the north central Pacific begins to lose its grip over the
area. Some degree of upper-level troughing will be a fixture
during the coming week as the jet nestled within its southern
flank directs a steady dose of cirrus from the lower latitudes and
into area skies. As has been the case during the last couple of
days, cirrus will be mostly transparent but even batches of
partially opaque high cloud will be sufficient to take the edge
off of daytime heat. Locally breezy trades will deliver periods of
trade wind showers to windward zones for the remainder of the
week, but continued stability will help limit rainfall amounts.
Strong easterly trade winds will prevail into tonight, with
clouds and showers favoring windward and mountain locations.
Periods with MVFR CIGS/VSBYs are expected in and around passing
showers through the early morning hours.
AIRMET Sierra remains in effect for mountain obscuration over
windward areas of Maui County and Oahu. Conditions may improve
through the late morning hours.
AIRMET Tango remains in effect for low-level mechanical
turbulence leeward of mountains due to strong trades.
A strong surface high will remain centered far N of the islands
through Friday, then build eastward next weekend. Except for a
brief period of somewhat lighter trade winds around midweek, when
the pressure gradient over the area may ease a little, fresh to
strong trade winds will prevail for the foreseeable future. As a
result, a Small Craft Advisory (SCA) for the windier zones around
Maui and the Big Island has been extended into Friday. All other
waters have been removed from the SCA except the Kaiwi Channel.
No significant swells are expected over the next several days. The
strong trades will support rough and choppy surf along E facing
shores for the next day or so, with surf and seas easing somewhat
Wednesday and Thursday as the upstream fetch diminishes. Minimal
swell energy from the S and SE is expected for most of this week,
but a long-lived run of near- to above- average surf along S
facing shores is expected to begin late next weekend, as a strong
low pressure passing SE of New Zealand sends long-period swells
our direction. A small, long-period swell from the E may arrive
early next week, generated by east Pacific Hurricane Bonnie.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
Small Craft Advisory until 6 AM HST Wednesday for Kaiwi Channel.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office