Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 302026
Area Forecast Discussion
National Weather Service Honolulu HI
1026 AM HST Thu Mar 30 2017
UPDATED BY NWS SAN FRANCISCO BAY REGION
Light trade winds over the western end of the state will allow
for leeward afternoon sea breezes over Kauai and Oahu today, which
will leave to increasing afternoon clouds and brief showers.
Moderate trade winds will continue over the rest of the state with
passing windward showers. Trade winds will become breezy over the
weekend with increasing windward rainfall expected.
Overall current forecast appears to be on track with the main
synoptic feature is the high pressure to the northeast of the
state that is helping to bring down the trade winds to the
eastern part of the state.
Have been watching the radar through the morning and did not a
couple of bands of moderate showers traveling across the Big
Island earlier. In fact, the showers caused Hilo to drop to less
than 2 miles of visibility earlier with a heavy shower.
To the west...lighter winds are allowing for more sea breeze
interactions which will help to kick off clouds and a few showers
for the afternoon into the evening hours.
Trade winds will increase tomorrow as high pressure builds toward
the north. More pronounced trade wind pattern is forecast over
the weekend which will bring breezy values and showers mainly
impacting windward and mauka areas.
Heading into the middle of next week, trade winds will weaken as
the high pressure weakens and a cold front passes by to the north
of the islands.
Only minor changes were made for the 18Z TAFs. Moderate trade
winds will be the main influence for all locations for the next
several days. Look for clouds/showers to continue to favor
windward and mountain area. Local MVFR CIGs and VIS at times
possible for those locations especially during showers. Rest of
the terminals should stay VFR. No AIRMETs anticipated.
Main story remains the large west-northwest swell (290-310 deg)
associated with a strong weather system far northwest of the state
that wilw reach the islands tonight, peak Friday and Friday
night, then slowly ease over the weekend. Warning- and/or
advisory-level surf for exposed north- and west-facing beaches is
expected during this time and will likely be issued in the
afternoon package. Latest models reamin in close agreement for
seas to ramp up quickly tonight to Small Craft Advisory levels and
peak in the 10 to 14-ft range Friday into Friday night, before
slowly easing through the weekend. If the swell comes in larger or
later than predicted, warning-level surf could would continue
into Saturday before dropping to advisory levels Sunday.
Local winds and seas will likely remain below advisory levels
through tomorrow as the ridge of high pressure north of the state
slightly weakens in response to a cold front that is forecast to
approach the region later in the week. Advisory-level trade winds
will return across portions of the waters over the weekend as high
pressure builds north of the state behind this front.
Surf along east-facing shores will remain small and choppy due to
moderate to fresh onshore winds. Surf will begin to build over the
weekend as trade winds strengthen locally and upstream of the
islands, and may near or reach advisory levels along east-facing
shores by the end of the weekend and into early next week.
A slight increase in surf along south-facing shores is possible
today through Saturday due to a long-period swell (190 deg) from
recent activity across the southern Pacific. In addition to this
south swell, wrap from the previously discussed large west-
northwest swell will add some to the mix by Friday at select spots
along exposed southern facing beaches.