Area Forecast Discussion
Issued by NWS Honolulu, HI
FXHW60 PHFO 300702
Area Forecast Discussion
National Weather Service Honolulu HI
902 PM HST SUN MAY 29 2016
The remnants of a front will provide a wet trade wind pattern for
some of the islands through at least the first half of the work
week. The front...now over Kauai...will push slowly through Oahu
later this evening...and through most of Monday. The front is
slated to ease on to Maui County Monday night and dissipate there
Tuesday. The remnant moisture...however...will linger around Maui
County through at least Wednesday. High pressure building north of
the island chain will bring gradually strengthening trade winds
through Monday, which will focus most of the clouds and showers
over windward slopes and coasts. Trade winds may diminish again
over the upcoming weekend.
A few showers sprung up late this afternoon, affecting a good
part of Honolulu, the Waipahu, and airport areas. These showers
continues to dissipate in the airport and downtown Honolulu. A
heavy shower also sprung up on Lanai late this afternoon
warranting a flood advisory which was cancelled a few minutes ago.
The situation is gradually changing as a front now in the Kauai
Channel continues to inch toward Oahu. Arrival time for the front
reaching Oahu is around midnight. It is then on to Molokai Monday
afternoon. The front falls apart as it edges further east to the
rest of Maui County Monday night and Tuesday. Trade winds filling
in behind the front will keeping the remnant moisture locked on
the windward sections of primarily Molokai and Maui through
at least Wednesday. The ECMWF and GFS solutions differ on what to
do with the remnant moisture. The latest GFS solution now keep the
moisture in Maui County, while the old ECMWF run, has the moisture
leaking onto the Big Island Wednesday. The POP grids from mid-
week through the end of the week is a blend of these two
solutions, featuring relatively high windward POPs statewide.
The front is accompanied by a mid- and upper level trough with
its axis east of the islands. However...the models are indicating
a shortwave trough pushing south across the islands Monday evening
on the back side of the mid and upper level trough.
The temperature at the mid levels will be be a warm minus 3
degrees C. Dynamically, it does not favor extreme weather like
thunderstorms, but there is a potential that the persistent and
constant trade showers can still cause some flooding issues that
we will be monitoring closely for.
As for the trades...the forecast calls for gradually strengthening,
mostly moderate trades to spread over Kauai tonight, Oahu on
Monday, and Maui county Monday night and Tuesday as a 1025 mb
surface high pressure moves to a position 720 miles north of
Kauai and Oahu. The trades weakens after Thursday as the surface
high supplying the islands breaks down. The islands transition to
a convective daytime sea breeze regime about Friday and last into
the weekend as a trough replaces the high north of the islands.
VFR will prevail over most areas through the night and into
Memorial Day, as daytime cloudiness and showers dissipate.
However, a weak front that will be moving over Kauai and, a bit
later, Oahu may generate TEMPO MVFR conditions over those isles as
it heads east and southeast this evening and overnight. More
daytime convective clouds and showers will likely develop over
Maui County and the Big Island by the late morning and afternoon
hours Monday as the front approaches those areas. MVFR will mainly
affect interior and mauka locales.
An AIRMET for mountain obscuration remains in effect for Kauai and
the Big Island this evening as low ceilings hold for the time
being. The AIRMET will be cancelled later as the cloudiness
As a weak front presses slowly across Oahu and Maui County the
next few days, a modestly strong trade wind regime will ease over
the surrounding waters of these islands. The winds are forecast to
remain below small craft advisory level. However, some of the
typically windier spots may come close to this level and will be
monitored closely. the surface high supplying the trades has a
central pressure value to 1025 mb while parked 720 miles north of
Kauai Tuesday morning. The high weakens there north of Kauai
after Thursday, and gets replaced by a trough over the weekend.
A small northwest swell should gradually increase tonight, peak
Monday, and subside into Tuesday. Buoy 51101 has about a 4 foot
northwest swell this evening with a 13 second period. The period
reached 14 seconds earlier this afternoon. The swell should have
reached Kauai about now, and Oahu later tonight. The current
small southwest swell will continue to decline tonight. 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.