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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 200010
Area Forecast Discussion
National Weather Service Honolulu HI
210 PM HST Sun Feb 19 2017
Updated Big Island Interior and Big Island summit zones to add a
slight chance of thunderstorms to the forecast. Some snow and or
freezing rain is also possible over the summits.
Breezy to locally windy trade winds can be expected through the
middle of the week as high pressure build in north of the state. A
few light showers can be expected over windward and mauka areas.
with most leeward locations remaining dry. Winds will drop off and
become more northerly later in the week as an area of low pressure
develops far north of the area.
.PREV DISCUSSION.../ISSUED at 10 AM HST SUNDAY/
Clouds associated with a dissipating cold front presently lies
across east Maui and The Big Island. A few light showers can be
expected with the front as is continues to move to the east
southeast. A broad swath of mid and high level clouds can be seen
on satellite imagery moving over the west end of the state with
the thickest cloud elements presently moving over Kauai and the
adjacent coastal waters. These clouds are expected to linger over
portions of the area through tonight before thinning out and
moving away to the east on Monday.
Breezy to locally windy trade winds will continue through
Wednesday with high pressure residing north of the area. The
airmass will remain rather dry and stable with precipitable water
values remaining below an inch. Shower activity will remain rather
limited with just brief passing light showers focused over
windward and mauka areas.
Later in the week an area of low pressure will develop far to the
north of the area. This will weaken the pressure gradient across
the area and turn our winds to a more northerly direction.
Generally dry weather will prevail for the most part with clouds
and a few showers continuing to fall primarily over windward and
A weakening cold front over the Big Island will bring low clouds
and showers with MVFR/IFR ceilings to the northern and eastern
slopes through the afternoon. The smaller islands will see mostly
VFR conditions with brief periods of MVFR with low ceilings in
Strong northeasterly surface winds will produce areas of
moderate mountain wave turbulence mainly over mountains and south
through west of all islands today. An upper level cloud band
over Oahu and Kauai may produce periods of moderate icing
AIRMET Sierra is in effect for mountain obscuration across
northern through eastern sections of the Big Island. The mountain
obscuration will likely continue through much of the day.
AIRMET Tango is in effect for moderate low level turbulence over
and downwind of all islands today.
AIRMET Zulu is in effect for moderate icing over Oahu and Kauai in
layer 150-FL220. Icing conditions will continue through the
Strong high pressure will build north of the state today in the
wake of a cold front moving down the island chain. This will
continue strong to gale-force winds over the waters through
Monday. Gales are expected across the Pailolo and Alenuihaha
Channels, as well as Maalaea Bay this afternoon through Monday
before gradually trending down Tuesday through Wednesday. Local
winds out of the north this morning will veer to the northeast
this afternoon through Monday and more toward the east Tuesday.
The overnight ASCAT pass clipped the Kauai waters and showed winds
up to 25 kt out of the north. These winds will generate very rough
/short- period seas across the local waters through the early part
of this week.
In addition to the winds and rough seas, a large north-northwest
(330-350 deg) swell will fill in across the waters today, peak this
evening/overnight, then gradually ease Monday through Tuesday.
This swell is associated with a storm-force low just under 1000
nautical miles north of the state. Buoy 51101 observations
(northwest of Kauai) continue to climb this morning, remaining in
line with the latest wave model guidance, if not slightly higher
than the model-predicted heights.
Surf along exposed north and west facing shores will quickly respond
and reach advisory levels today as the north-northwest swell fills
in. These conditions will continue through Monday before trending
down. The northern shores of the Big Island will be monitored for
possible inclusion in the advisory with the afternoon package as
the storm passes well to the north later tonight through Monday. Surf
along east facing shores will gradually rise through the week and
near advisory levels Tuesday through Wednesday as the winds veer
out of the east.
On Wednesday, a moderate long-period west-northwest (310 deg) swell
associated with a developing gale east of Japan is expected to fill
in, peaking late Wednesday through Wednesday night. This swell
will gradually ease Thursday, before a reinforcing swell from the
same direction, but longer period, builds in early Friday
morning. If this source comes in slightly higher than predicted,
advisory- level surf along north and west facing shores will
become a possibility beginning Wednesday and Wednesday night,
though an advisory looks more solid for the Friday time frame.
High Surf Advisory until 6 PM HST Monday for Niihau-Kauai
Windward-Kauai Leeward-Oahu North Shore-Oahu Koolau-Molokai-Maui
Windward West-Maui Central Valley-Windward Haleakala.
Wind Advisory until 6 PM HST Monday for Lanai-Kahoolawe-Big
Island North and East-Kohala.
Small Craft Advisory until 6 PM HST Monday 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-Big Island
Windward Waters-Big Island Leeward Waters-Big Island Southeast
Gale Warning until 6 PM HST Monday for Maalaea Bay-Pailolo
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office