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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 080615
Area Forecast Discussion
National Weather Service Honolulu HI
815 PM HST Fri Aug 7 2020
Breezy trade winds will prevail through the weekend, then trend
down Tuesday through midweek as high pressure to the northeast
weakens. Clouds and showers will favor windward and mountain
areas each day, especially through the overnight and early
morning periods as pockets of moisture move through. Windward
shower coverage may decrease later in the weekend and into early
next week some drier air moves into the area.
Latest surface analysis and satellite imagery showed the
subtropical ridge anchored north of the islands and patchy low-
level clouds approaching and moving through from east to west.
Some of these clouds are generating brief/mostly light showers as
they move through - especially over the western end of the island
chain where a band of higher than average moisture (PWs up to 2
inches) has setup. Rain gages around the islands reflected this
and showed peak accumulations up to near an inch on Kauai in the
past 12-Hrs (through 7 pm HST). Elsewhere, accumulations ranged
from a few hundredths to a quarter of an inch through this
period. Expect the showery and breezy pattern to hold into the
weekend in response to this area of higher moisture lingering in
Guidance has initialized well with the current pattern and shows
upper heights gradually rising through the weekend as the the upper
trough that moved over the past couple of days through continues
westward and away from the area. This combined with PWs trending
back down toward normal will translate to a slightly drier and
more stable trade wind pattern returning by or around Sunday.
Trades will become brisk through this time as high pressure
strengthens to the north, but should trend down through the first
half of next week. Another area of lower heights moving in aloft
early next week could enhance shower coverage once again through
midweek, mostly for windward and mountain locations.
Moderate trades predominantly out of the east have been relatively
dry today suggesting AIRMET SIERRA will not be required in the
near term. Improved moisture spreading back into the area during
the latter half of the period will bring an increased likelihood
of periodic showers and MVFR/mountain obscuration for windward
AIRMET TANGO remains in effect over and immediately south thru
west of mountains below 9000 feet for tempo moderate turbulence.
High pressure to the north-northeast is expected to strengthen
this weekend, which will boost trade winds across the coastal
waters. The Small Craft Advisory (SCA) for the typical windier
areas near Maui County and the Big Island expands to include Maui
Windward Waters, the Kaiwi Channel and Oahu Leeward Waters
Saturday morning, through Sunday afternoon. Wind are expected to
trend down early next week, which should once again bring the SCA
level winds to the typical areas near Maui County and the Big
Surf along south facing shores is expected to return to
background levels by Saturday, and remain below summer average
into next week. Small short period southeast swell will continue,
with the Big Island blocking some of that energy from reaching the
smaller islands. Surf along east facing shores will build through
the weekend as trade winds strengthen, but is expected to remain below
the advisory levels. A small north-northwest swell will provide
a bit of energy to the north facing shores, keeping surf just
above flat through Saturday.
Small Craft Advisory until 6 PM HST Sunday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
Small Craft Advisory from 6 AM Saturday to 6 PM HST Sunday for
Oahu Leeward Waters-Kaiwi Channel-Maui County Windward 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