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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 261324
Area Forecast Discussion
National Weather Service Honolulu HI
324 AM HST THU MAY 26 2016
A destabilizing upper trough will move east of the islands today,
decreasing the chance for enhanced showers and allowing our
airmass to gradually stabilize. However, surface troughing will
keep winds lighter than normal through next week. Daytime sea
breezes and nighttime land breezes will prevail this weekend.
Satellite loop shows the axis of an upper trough passing eastward
across the islands this morning. This upper trough, combined with
abundant low level moisture, produced bouts of heavy showers
overnight, mainly across portions of Oahu. This activity has
decreased dramatically over the past few hours. The upper trough
axis is expected to continue sliding east through the day today,
allowing our airmass to gradually stabilize. Enhanced showers may
still occur briefly this morning, but a transition to a drier
convective pattern is expected as the upper trough departs.
Surface winds are lighter than normal and veered to the east
southeast thanks to the proximity of a stalled front northwest of
the state and additional surface troughing near Kauai. These
features are working to slacken the pressure gradient across the
islands, hampering the influence of strong centers of high
pressure far northeast and northwest of the state.
Models show trade winds will be rather light through the weekend
as a surface trough is expected to form over the islands. Daytime
sea breezes will produce clouds and showers over interior and
leeward areas while land breezes bring partial clearing at night.
Light winds will allow volcanic haze from Kilauea to spread over
the smaller islands. We expect trade winds will return starting on
Memorial Day as the surface ridge rebuilds north of the islands.
The trades may remain lighter than normal through next week since
troughing aloft will keep the subtropical ridge weak.
Brief reductions to cig/vsby will be possible in passing -SHRA
mainly over mountain and north thru east sections of the islands
through mid morning. The highest probabilities for rain are
expected over windward sections of Oahu, Molokai, Maui and the Big
Island. This afternoon showers are expected to develop over the
mountains and interior of the islands, with some reductions to
cig/vsby once again possible. The showers should diminish in the
evening with loss of daytime heating.
Airmet Sierra remains in effect for mountain obscuration across
Oahu, Molokai and Maui. Conditions should improve here later this
morning, and the Airmet will be cancelled at that time.
Combined seas will remain below small craft advisory threshold
through the forecast period.
A moderate southwest swell arriving from the Tasman sea is
expected to peak late today and Friday, then decline during the
weekend. Since there are so many islands along the path of the
swell, surf is likely to be inconsistent. See the the
Collaborative Nearshore Swell and Wind Forecast (SRDHFO) for
details on this swell. Otherwise rather small surf is expected.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office
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It was last modified on: Wed, Dec 17 2014 - 1841 UTC
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