Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 301621 CCA

Area Forecast Discussion...corrected
National Weather Service Honolulu HI
412 AM HST MON MAY 30 2016

A front will provide a wet trade wind pattern for some of the
islands through the new work week as it moves slowly down the island
chain. The front, now near Oahu, will stall and gradually dissipate
over the Big Island during the second half of this week. The trade
winds will strengthen today through Tuesday to moderate speeds.
After prevailing through most of the week, trade winds are expected
to diminish again next weekend.


As of 330 am HST, the front is in the Kauai Channel. It is having a
difficult time advancing on to Oahu, likely due to an offshore land
breeze coming off the north shore. The front should continue
eastward across Oahu later this morning and to Molokai this
afternoon. The front continues on to the rest of Maui County tonight
and Tuesday. The models keep the front together while moving through
Maui Tuesday night and on to the Big Island Wednesday. The GFS has
the front stalling over the Big Island through at least Friday while
the ECMWF model has the front moving south of the Big Island on
Friday. These models could be keeping the front as a feature too
long. The front will disperse once the trades turns east to west
which is about Friday.

As noted in the previous discussion, the slow moving nature of
this front and with its persistent and almost continuous trade
showers may lead to some flooding issue and mud slides on the
windward side of the larger islands from especially Molokai to the
Big Island this week. The moisture is shallow with cloud tops no
higher than 12k feet but this moisture will be plentiful acting on
an orographic barrier. So we will be monitoring the situation
closely this week.

As for the trades winds...the forecast calls for gradually
strengthening to mainly moderate speeds tonight and Tuesday. This
is a result of a 1025 mb surface high moving to a position about
720 miles north of Kauai tonight. The trade wind starts weakening
after Thursday as the high starts to break down. The islands will
then transition to a convective daytime sea breeze mode about
Friday and persist through the weekend. The high north of the islands
will be replaced by a trough.


VFR will prevail over most areas through Memorial Day. However, a
weak front that has been moving over Kauai and is approaching Oahu
may generate TEMPO MVFR conditions in northern and windward
sections of these isles as it continues to head east and
southeast. More daytime convective clouds and showers will likely
develop over Maui County and the Big Island by the late morning
and afternoon hours today as the front approaches. MVFR will
mainly affect interior and mauka locales on those islands.

No AIRMETs are currently in effect.


As a weak front presses slowly across Oahu and Maui County during
the next 24 hours, a modestly strong trade wind regime will build
over the surrounding waters of these islands. The winds are
forecast to remain below small craft advisory level. However, some
sections of the coastal waters may come close to small craft
advisory level criteria. We will be monitoring closely for these
conditions. We will lose the trades again late this week as the
source of the trades, a high pressure system 720 miles north of
kauai, dissipates and is replaced by a trough.

A small northwest swell should gradually increase over the islands
this morning, peaking later today, before subsiding into Tuesday.
The Waimea is currently reading 2 ft 13 seconds. The south swell
is also holding well as noted by the Lanai buoy with a reading of
2.3 feet at 15 secs.

Another small southwest swell is expected to bump surf up slightly
again for south shores Wednesday. The return of strengthening
trade winds will gradually re-introduce short period choppy surf
to east facing shores during the coming week.





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