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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 261326
Area Forecast Discussion
National Weather Service Honolulu HI
326 AM HST Wed Oct 26 2016
Trade winds will persist across the main Hawaiian Islands through
the forecast period, becoming stronger tonight through the weekend
due to building high pressure to our north. A weak frontal cloud
band expected to pass southwestward across the islands later today
and Thursday will bring increased shower and cloud coverage, but
only light to moderate total rainfall. An upper trough may cause
showers to increase once again this weekend.
A ridge of high pressure, anchored by a 1031 MB high near the
dateline, extends through 39N180W, 33N160W and 33N140W this
morning. Moderate to locally strong trade winds persist across
local waters, with drier trade flow noted this morning versus 24
hours ago. Clouds and showers favor windward areas, as is normal
with trade flow.
Models show the remnants of a weak frontal band will pass
northeast to southwest across the main island chain later today
and Thursday. This feature will cause clouds and showers to
briefly increase, but only light to moderate rainfall amounts are
expected. Trade flow at the surface will persist as the frontal
band passes, becoming stronger as the following high moves east of
the dateline and strengthens. We expect stronger trade winds to
dominate across the area from Thursday through the weekend.
Upper level ridging will keep a cap on showers through Friday
afternoon, with only light to moderate rainfall amounts expected
within trade showers. An upper level trough is expected to push
southeastward across the state Friday night and bring cooler
temperatures aloft over the islands. The cooler temps will
increase instability and trigger increased shower coverage and
intensity Friday night into the weekend. Overall, expect a wet
trade wind pattern over the weekend and into next week.
High pressure to the northwest of the Hawaiian Islands will
continue to drive northeasterly trade winds through the TAF
period. Meanwhile the dry airmass over the state this morning
will give way to increasing moisture in the afternoon. Patchy
clouds and showers along windward slopes and coasts this morning
will thus increase towards evening. And low topped convective
clouds will develop over leeward Big Island in the early afternoon
afternoon and linger through the late evening hours.
AIRMET TANGO could become necessary over the southern half of the
state this morning as an area of high level turbulence passes just
to the southeast of the state.
Moderate trade winds with locally breezy conditions will remain
through today before the trade winds ramp up once again. The
typically windier waters around the Big Island and Maui County
will see Small Craft Advisory conditions through this time before
spreading across all waters, likely by Thursday.
The current west-northwest swell is producing High Surf Advisory
conditions on the north and west shores of Kauai and the north
shores of Oahu. A High Surf Advisory remains posted through noon
today for these areas. Blocking from the western islands and the
west-northwest nature of this swell will help keep surf below
advisory conditions on the west facing shores of Oahu and the
north and west facing shores on Molokai, Maui, and the Big Island.
This swell is expected to begin to lower by this afternoon. A
series of smaller north-northeast and northwest swells will then
fill in through the weekend, but surf is expected to remain well
below advisory levels. For the south facing shores a small long
period swell will bump surf up slightly today into Friday. A long
period east swell is possible this weekend from the distant
Hurricane Seymour in the Eastern Pacific.
High Surf Advisory until noon HST today for Niihau-Kauai
Windward-Kauai Leeward-Oahu North Shore-Oahu Koolau.
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
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
Send comments to: Ryan Lyman