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Hawaiian Islands Synoptic Discussion and Guidance

FXHW60 PHFO 051414

Area Forecast Discussion
National Weather Service Honolulu HI
414 AM HST Mon Dec 5 2016

The inclement weather continues for the Hawaiian Islands this
week. The western half of the island chain will have a brief
break in the unsettled weather today and Tuesday before another
round of weather moves in for the second half of the work week.


Some minor adjustments were made to the grids but the philosophy
reasoning behind the forecast remains pretty much intact.
Basically, a wet and active weather pattern continues for the
Hawaiian Islands for this week. Today and Tuesday will be
somewhat of a break in the weather for Kauai, Oahu, with a bit
more sun as an upper level trough pushes eastward thereby taking
and thinning some of the dense layered stratiform mid and high
clouds away. The upper trough is slated to head northeast soon,
and would not be able to totally clear out these clouds across the
eastern part of the island chain. But a bit more sun under a
sufficiently unstable air mass, will likely lead to a couple of
thunderstorms /ts/ across Maui and the Big Island especially this

Currently, most of the steady but mainly light precipitation
associated with the dense layered clouds lies east of Oahu. The
surface trough meanwhile, continues to approach Niihau and Kauai
from the west as noted on the weather radar loop. Scattered
showers are also present in the convergent southerly flow in the
Kauai channel. We expect the surface trough to push past Kauai
County by mid morning and usher in a slightly drier more stable
airmass. We anticipate the air mass over Oahu to be more stable as
well by this afternoon. However, ample day time heating with ample
moisture and a sea breeze will result in some scattered showers
this afternoon. Although excessive rainfall is not expected at
this time for Oahu, we will continue to monitor the situation

The surface trough dissipates over Oahu later today while a weak
surface high forms north of the islands. With it, weak trades
returns briefly to the islands starting this evening and lasting
through early Tuesday evening. Thereafter, the southerly winds
takes over while the next surface trough shows up just west of
Kauai Wednesday morning. It should be noted the ECMWF solution
does not show this trough, instead has light trades across the
island chain. The GFS goes on to show the surface trough to stall
over Kauai and languish there through Thursday before dissipating
Thursday night. This surface feature will be aided by another
upper level trough that dampens out over the islands Thursday.
The models then shows another upper and surface trough combo
approaching Kauai Saturday morning, thereby prolonging the
inclement weather.

More to come.


An upper level trough over the central islands will keep
conditions unsettled over Maui and the Big Island today, with
improving conditions expected tonight as the upper trough
weakens. Occasional MVFR cigs/vsbys will be possible in SHRA here,
with isolated IFR conditions possible. Over Molokai and Lanai,
unsettled conditions and occasional MVFR cigs/vsbys are expected
through the morning hours, with improving conditions expected this
afternoon. Over Oahu and Kauai, more settled weather is expected,
although some afternoon shower development and brief MVFR
cigs/vsbys will be possible especially across the interior of the

AIRMET Sierra remains in effect for mountain obscuration from
Oahu eastward to the Big Island. Conditions are expected to
improve over Oahu later this morning. Molokai and Lanai should see
improving conditions by this afternoon, and Maui and the Big
Island may deal with mountain obscuration through much of the day.

AIRMET Tango is in effect for moderate upper level turbulence
between 150 and FL350 across all islands. These conditions are
expected to improve later this morning.

AIRMET Zulu is in effect for icing east of Kauai. These conditions
are expected to slowly improve from west to east across the island
chain through the day.


The Hanalei buoy shows a subsiding trend in the seas and northwest
swell. The Small Craft Advisory /SCA/ has been extended for
another 12 hours to 6 pm HST this afternoon but the area reduced
to waters around Kauai. No large swells are expected during the
next six days or meaning surf will remain below High Surf
Advisory levels.


Flash Flood Watch to 6 pm hst this afternoon for Maui and Big

Small Craft Advisory until 6 PM HST this afternoon for waters
around Kauai.




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
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