Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Honolulu HI
955 am HST Sat Oct 10 2015

a trough moving over the area today through early next week will
weaken the trade winds and allow sea breezes to produce afternoon
clouds and showers. Some of the showers may bring locally heavy
rainfall each afternoon and evening...with a slight chance of
thundershowers for The Big Island and parts of Maui County.
Trade wind weather will return by middle week as the trough

satellite imagery continues to show a band of showery clouds with
embedded isolated thunderstorms progressing into the windward Big
Island waters. This band is associated with moisture along a
trough moving westward in the mean trade wind flow. The
expectation is that this trough will stall across the eastern half
of the state over the weekend as the ridge to the north
weakens...cutting off the trades. This will bring light north
winds to Kauai...and light and variable winds to the rest of the
state into early next work week. With the higher amounts of
moisture drifting in today...we are looking at increasing rain
chances especially for Maui County and The Big Island. Models are
showing enough instability for deep convection to fire off this
afternoon...especially on the sunny leeward sides of The Big
Island...including Kona...kohala and saddle areas and leeward
Haleakala on Maui. Have issued an update to cover these ideas.
Expect a repeat of these moist and unstable conditions on
Sunday...but with a bit more morning cloud cover than today. Of
course with this deeper moisture coming in...the threat for
locally heavy rainfall is on the rise as well. Will continue to
monitor the situation closely for the need for any flash flood
related products...but at this time none are warranted.

The trough will weaken in place across the middle of the state on Tuesday
and Wednesday...with lingering moisture continuing to bring a chance
of afternoon showers through midweek.

A new ridge builds in far to the northwest of the state by
Thursday and Friday keeping the door open for a middle latitude
trough to the northeast of US to drag frontal remnants across the
state in moderate northeasterly trades. The initial frontal band reaches
Kauai Wednesday...and Oahu and Maui Thursday. The second frontal
band reaches Kauai Friday night and stalls across the middle of
the state over the next weekend. Expecting fairly wet weather on
the windward sides during this period.

Tropical Storm Nora...located about 1250 miles east southeast of
Hilo at 900 moving west and expected to strengthen. The
National Hurricane Center in Miami is forecasting Nora to move
into the central Pacific this evening.


deeper moisture...with precipitable water values maxing out over 2
inches...will continue to creep west from The Big Island and spread
over the central islands throughout the day. A surface trough has
set up just east of phto and convection has started to flair up this
morning. Cumulonimbus tops were reaching fl350-400. This trough will gradually
move west...and along with daytime heating there is a slight chance
for thunderstorms over The Big Island and its northeast adjacent
waters. The windward coast will likely see prevailing MVFR for most
of the day with pockets of IFR likely. Airmet Sierra for mountain
obscure is posted for Upolu Point through phto to volcanoes. On the
leeward side of The Big Island...generally VFR will continue into
the early afternoon then afternoon convective showers will become
more likely and the Kona slopes may see MVFR to isolate IFR conditions.

Lower clouds and showers have already started banking up along the
north and east slopes of Maui...and airmet Sierra for mountain obscure
is posted. Throughout the day showers will likely increase and
potentially cause tempo MVFR at phog and MVFR to isolate IFR along
other windward and mountain areas. As for phmk...Molokai will remain
on the fringe of the deeper moisture and clouds and showers will
focus along windward and mountain areas. Some shower will likely
carry MVFR conditions. Airmet Sierra for mountain obscure will be
expanded as needed.

Much more stable conditions remain over the western end of the
state. Mimic precipitable water shows a strong gradient between
Kauai and Big Island...where precipitable water values are less than
1.5 inches on Kauai. The 12z sounding from phli shows a strong
inversion between 7-8kft. For Kauai and Oahu...VFR will prevail with
clouds and isolated showers focusing along windward and mountain


winds and seas will remain below the Small Craft Advisory levels
through early next week. A south southwest swell from a low near
New Zealand will pass mostly off to the east of the islands but is
expected to bring advisory level surf to the south and west facing
shores of The Big Island through early Sunday morning. Moderate
northwest swells will continue for the next several days...but
surf from these swells is expected to remain below the advisory


Hfo watches/warnings/advisories...
high surf advisory until 6 am HST Sunday for south and west facing
shores of The Big Island.




National Weather Service Glossary of Abbreviations