Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
400 am HST Tuesday Jul 7 2015
trade winds will increase through middle of the week as high
pressure builds far north of the state. Low clouds and passing
showers will favor windward and Mauka areas and may reach the Lee
areas of the smaller islands as the winds strengthen.
trade wind weather continues across the islands early this
morning...with passing low clouds and showers affecting mainly
windward areas. Satellite imagery revealed an area of low clouds
reaching windward Big Island earlier this morning...bringing a
little more showers to that area. These clouds will spread west as
the day progresses...and may reach Maui County later this morning.
Early morning Lihue and Hilo soundings both revealed a typical trade
wind weather profile...with a slightly unstable air mass while low
level moisture is a little lacking on the Lihue sounding. Expect
trade wind weather will prevail today...as areas of surface high
pressure remain far north of the state.
In fact...trade winds are firming up slightly through the next
couple of days...as the surface high pressure areas far north
consolidate. Winds will gradually strengthen to fresh breezes by the
middle of the week. Air mass will remain a little more unstable as
an upper level trough currently east of the state is expected to
shift west in the coming days. Regardless...trade wind weather will
continue across the islands through the next few days...with passing
low clouds and showers affecting mainly windward and mountain areas.
Moderate showers may develop under the more favorable atmospheric
conditions...though these showers will be moving swiftly under the
moderate winds. Some of the showers may also reach the Lee areas of
the smaller islands under the winds.
A developing disturbance in the tropics located approximately 1300
miles east-southeast of Hilo early this morning will continue to
make the forecast for the later part of the week much more
challenging as latest model solutions still have this feature moving
west northwest...possibly reaching the vicinity of the state toward
the weekend. The track of this feature will have a great impact on
what weather the islands will experience. As a reminder...the
hurricane season is here and everyone should be prepared...please
use checklists and informational resources either on our website or
state civil defense.
high pressure north of the region will keep a moderate east-NE trade
wind flow in place through Tuesday...with clouds and showers focused
primarily across mountain and north through east sections of the islands. Can/T
rule out some brief MVFR ceilings at phli and phto...but generally VFR
conditions are expected through the taf forecast period.
VAD wind profile data from radars across the state along with the
phto and phli 12z soundings...indicate that winds have increased
enough to warrant an airmet for low level turb. As a result...have
issued an airmet for moderate turb blw 090 over and S through west of mountain all
islands. Still can/T rule out the need for an airmet due to mountain obscure
later this morning...and will continue to monitor conditions and
issue if necessary.
surf associated with the current southerly swells will remain above
advisory heights through Wednesday...thus the high surf advisory for
south facing shores continues. The current southerly swells will
gradually decline Thursday. Reinforcing southwest swells are
expected to increase surf again along south facing shores from
Friday through this weekend...though surf heights along south facing
shores are expected to stay below advisory level.
A Small Craft Advisory is in effect at least through Wednesday for
the typical windy coastal zones around Maui County and The Big
Island due to the winds. As the moderate to locally fresh winds will
likely continue through the week...small craft wind conditions may
spread to the other coastal zones later.
Strengthening trade winds combined with increasing east and
northeast swells may bring near advisory level surf heights along
east facing shores from Friday into this weekend.
high surf advisory until 6 PM HST Wednesday for south facing
shores of Niihau Kauai Oahu Molokai Lanai Kahoolawe Maui and Big
Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island leeward waters-Big
Island southeast waters.