|Wind||ESE 14 mph|
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Hawaiian Islands Synoptic Discussion and Guidance |
FXHW60 PHFO 202010
Area Forecast Discussion
National Weather Service Honolulu HI
1010 AM HST Tue Aug 20 2019
A surface ridge will remain north of the area. A weak trough south
of the Big Island will move west and weaken through this evening.
A front north of the islands will move south through Thursday,
then move away to the west. High pressure will build north of the
area over the weekend.
The 8 AM surface analysis shows a surface ridge extending from a
high far northeast of the area near 31N130W and another high about
600 miles northwest of the area near 30N163W. A weak trough south
of the Big Island is moving west around 10 miles an hour and
The ridge north of the islands will maintain easterly trade winds
across the area. A poorly organized area of showery low clouds
associated with the trough south of the Big Island has been moving
over the islands. Most of the showers have moved off to the west
of the islands, but some showers remain upstream of the Big Island
and Kauai. These showers will clear the islands this afternoon.
Trade winds will strengthen a bit through tomorrow as the high
builds northwest of the islands. A front about 1000 miles north of
the islands will move south through Thursday and cause the trades
to weaken. On Friday, the front will move off to the west and the
high will build northeast. Trade winds will strengthen again and
become locally breezy over the weekend.
An elongated surface high to the north of the state will help to
maintain moderate easterly trade flow through this afternoon.
Isolated showers, mainly concentrated along windward areas and
over elevated terrain, will become scattered after sundown this
evening. Expect MVFR conditions at times tonight from low clouds
No AIRMETs are currently in effect.
High pressure will strengthen north of the area providing an
uptick in trade winds speeds. Small Craft Advisory conditions are
expected beginning tonight over the windy waters around Maui
County and the Big Island.
Data from the PacIOOS buoys show a new long period south swell
continues to build. Surf along south facing shores will continue
to rise today with heights expected to reach High Surf Advisory
levels. This swell will hold solid through Wednesday then lower
gradually Thursday and Friday. A series of smaller long period
southerly swells are expected early next week.
A small west to northwest swell will linger over the next few
days providing some out of season surf along exposed shorelines.
Strengthening trade winds over the next several days will cause
short period choppy surf to increase along east facing shores
through the remainder of the week and on through the weekend.
High Surf Advisory from midnight tonight to 6 AM Thursday for
south facing shores of all islands.
Small Craft Advisory from 6 PM this evening to 6 PM Thursday for
Maalaea Bay, the Pailolo and Alenuihaha Channels and waters south
of the Big Island.
Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office