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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 220632
Area Forecast Discussion
National Weather Service Honolulu HI
832 PM HST Fri Feb 21 2020
High pressure far northeast of the state will track further away,
resulting in weakening trade winds and fewer showers this
weekend. A front will approach from the northwest, then stall and
weaken before reaching Kauai. Trades will gradually strengthen
again during the first half of next week.
A strong surface high far northeast of Hawaii continues to slowly
track eastward. As a result, trade winds will weaken through the
weekend. For tonight, expect mostly dry weather with moderate
trade winds. A few passing light showers may impact windward areas
Winds will be noticeably weaker Saturday as they veer out of the
east southeast with the approach of a cold front. Winds will
become light and variable by Saturday night and remain so into
Sunday, allowing sea breezes and interior clouds to set up Sunday
afternoon, followed by clearing at night.
The front will weaken and stall just northwest of Kauai on Monday,
with little direct impact to the state. High pressure behind the
front will usher in trades that will overrun the front and reach
the islands Monday into Monday night. Trades will strengthen
during the first half of next week and bring additional clouds
and showers to windward locations through the remainder of the
week. Trades may become breezy through the second half of the
week, resulting in showers reaching leeward sides of the smaller
islands. Models show an upper trough digging southward across the
Big Island next weekend, but with large differences in timing and
Mainly VFR conditions expected tonight. The only areas of concern
for MVFR visibility and ceiling are along the windward slopes and
coasts of the islands due to low clouds and SHRA. AIRMET Tango
remains in effect for tempo moderate low-level turbulence over and
downwind of the terrain, but winds are abating tonight and the
AIRMET may be dropped by morning. Winds will turn ESE Saturday as
a front approaches from the NW.
A strong high remains far northeast of the area, with a ridge
extending back toward the southwest. The pressure gradient south
of the ridge is producing breezy to strong easterly trade winds
over the coastal waters. A Small Craft Advisory (SCA) remains in
effect through tonight for the coastal waters around the Big
Island and Maui.
The high will move southeast over the next couple of days, with
winds easing and veering to the southeast over Hawaiian waters as
the high moves farther away. Meanwhile, a front will approach
from the northwest, with a trough forming ahead of the front over
the northeast coastal waters. The front will enter the northwest
offshore waters Sunday night, then dissipate. A new high moving
east behind the front will bring a return of trade winds across
Hawaiian waters by Monday night.
Surf will remain elevated along east facing shores of the islands
due to strong trade winds, but surf has dropped below the High
Surf Advisory threshold. This surf will continue to gradually
subside through early next week as the trades fade.
A new northwest swell arriving tonight will peak Saturday, then
gradually lower Sunday through Monday. Surf from this swell will
remain below the advisory threshold. A very large northwest swell
is expected to arrive Monday night. Surf from that swell will
peak well above the advisory level Tuesday, and the surf will
likely reach warning levels along north and west facing shores.
Surf will remain small along south facing shores.
Small Craft Advisory until 6 AM HST Saturday for Maui County
Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo
Channel-Alenuihaha Channel-Big Island Windward Waters-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