Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
830 PM HST Monday Apr 27 2015
a stalled front over northern Big Island will dissipate through
Tuesday. This will allow the strong and gusty trades to spread to
and around The Big Island. Breezy trades will persist through the
rest of the week as a strong high pressure cell passes slowly north
of the islands. The strongest winds is expected Wednesday. Under
this trade wind regime...showers will be favoring the windward
and mountain areas of all islands for the rest of the week with a
few of these showers drifting downwind into the leeward areas of the
smaller islands. Leeward Big Island will have a few showers each
afternoon for the rest of the week.
as we return to a more normal trade wind regime...we must still deal
with the dissipating front. Satellite loop shows the mass of clouds
over windward Maui and Molokai gradually drifting westward towards
Oahu and Kauai. These clouds are part of the front that had stalled
over Maui last night...and is now in a dissipating state...where the
elements are being carried westward as the winds veers a bit from
the NE to east-northeast. So Oahu...which has been dry today...will have an
uptick in trade showers tonight and most of Tuesday. Maui and
Molokai...on the other hand...will be a tad drier Tuesday.
Windward Big Island will also see an uptick in trade showers as we
return to a more normal trade pattern during the next 24 hours.
No real organized features such as old fronts or bands to be
affecting the islands until Thursday night and Friday. So in the
mean time...it will be the normal distribution of clouds and showers
upwind of the islands. The windward and mountain areas will gather
in most of the rain...but a few of these showers will be carried
into the leeward areas of the smaller islands...especially nights
and mornings. Leeward Big Island will have their usual afternoon
clouds and a few showers.
The source of the strong trades is a 1035 mb surface high located
900 miles north-northwest of Kauai this evening. A passing trough at the middle
levels will hinder the trades from strengthening in the next 24
hours with the strengthening process resuming Tuesday night. Still
middle level ridging following in is not expected to be all that
strong so that the low level inversion is not well establish to
favor downslope. We expect the strongest winds for the islands to
occur between Tuesday night and Wednesday night as the high passes
directly north of the islands. The trades eases off slightly
thereafter at moderate to locally strong for the rest of the week.
Strong high pressure north of the islands will keep strong NE trade
winds going through Tuesday. A dissipating front over the central
islands will keep enhanced clouds and showers affecting mainly north
through east sections of the central and northern islands through the
overnight hours. As a result...MVFR ceilings and/or visibilities can be
expected to occasionally affect phli...phmk...phny...phog...and phto
through the overnight hours. Some improvement in conditions is
expected later tonight as the moisture associated with the decaying
front begins to lift northward and away from the islands.
Airmet Sierra is in effect for mountain obscuration for portions of
each island...with conditions likely to continue through much of the
Airmet Tango remains in effect for low level turb over and to the S
through west of the mountains from Kauai to Maui...and these conditions
will likely continue through Tuesday.
all buoys on the windward side except Hilo have increased in sig
wave heights to between 10 and 15 feet. Thanks to the strong trades
and a north swell. This north swell will turn more northeasterly
Tuesday...so the advisory for north facing shores of the smaller
islands will be lowered late Tuesday...and the advisory for the east
facing shores of the smaller islands will continue through early
Small Craft Advisory /sca/ is in effect tonight for all but the
waters of windward Maui...windward Big Island...and waters west and
south of The Big Island. There will be a change in this Small Craft Advisory
configuration with the expansion of the Small Craft Advisory to waters west and south
of The Big Island...and the lowering for the leeward waters of Maui
County. We will be reevaluating this overnight.
high surf advisory until 6 PM HST Tuesday for north facing shores of
Niihau Kauai Oahu Molokai and Maui.
High surf advisory until 6 am HST Thursday for east facing shores of
Kauai Oahu Molokai and Maui.
Small Craft Advisory from 6 am Tuesday to 6 am HST Thursday for
waters south of The Big Island.
Small Craft Advisory until 6 am HST Tuesday for Maui County
leeward waters-Big Island windward waters.
Small Craft Advisory until 6 am HST Thursday for waters west of