Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Honolulu HI
830 PM HST Monday Aug 3 2015
the trade winds will remain light to moderate through Tuesday with
just a few passing showers expected. Tropical Storm Guillermo is
forecast to pass near the eastern part of the island chain on
Wednesday...then continue towards the western part of the island
chain on Thursday. A moderate to locally strong trade wind flow will
return Friday and into the weekend.
moderate trades will continue tonight and through Tuesday as high
pressure centered far north of the main Hawaiian islands remains in
place. An upper level ridge across the area is keeping relatively
dry and stable conditions over the smaller islands...which should
prevail until late Tuesday. Any passing showers that may form will focus
over mountain areas...and a few may briefly move into interior and
leeward areas at times. On The Big Island...a more humid airmass
lingers with precipitable waters on the 00z Hilo sounding remaining around 1.79
inches. Thus...expect enhanced cloud cover and showers mainly over
windward areas of The Big Island tonight and Tuesday.
The Central Pacific Hurricane Center continues to monitor the
progress of Tropical Storm Guillermo...located about 500 miles east-southeast
of Hilo and moving northwest at 10 miles per hour. The current forecast keeps
Guillermo slightly north of the state. However...it remains close enough
to the islands to keep some areas within the forecast track/S Cone
of error. The intensity of Guillermo is forecast to be tropical
storm strength as it nears the main Hawaiian islands on Wednesday.
A tropical storm watch is in effect for The Big Island and all
islands of Maui County through Thursday at noon. Please see the
tropical storm local statement on our website...product hlshfo...for
more specific information of The Hazards Guillermo is expected to
bring. We will continue to assess the situation to determine if
more parts of the state need to be added to the watch area or any
areas need to be upgraded to a warning later tonight or on Tuesday. A
hydrologic outlook is also in effect to outline the flood potential.
Once Guillermo clears the area...global models are in fair agreement
in bringing back a more typical trade wind weather regime for the
end of the week and weekend.
the current airmet for mountain obscure for windward Big Island will
continue in the short term as conds continue to improve there.
There is a chance the airmet will be lowered for the midnight
package. The Lee side of The Big Island has a heavy layer of clouds
but they appear to be high base at 6k feet with tops to 15k feet.
Conds there will be slow to clear as the evening progresses. A late
night shower is possible along the Kona coastline later this evening.
This cloud mass over the Big Islands bleeds over to Maui County.
Again this layer appears to be high based stratocumulus at 6k feet.
Near the surface...a moderate NE wind flow prevails...not strong
enough to require an airmet turb. This flow will be carrying a few
spotty showers that will affect the windward and mountain areas of all
islands...not enough to warrant an airmet however.
So...except for windward Big Island...expect VFR conds to prevail
early on...then all areas after 10z.
a high surf advisory is in effect for east facing shores of The Big
Island through Tuesday 6 PM.
A tropical storm watch is in effect through Thursday at noon
for coastal waters adjacent to The Big Island and Maui County in
the advance of Guillermo. See advisory list below for the
affected zones and mwwhfo for more specific information. A watch
means that tropical storm conditions will be possible. Offshore
waters...those waters from 40 nm to 240 nm away from the main
Hawaiian islands...are under a Tropical Storm Warning.
tropical storm watch for Molokai-Lanai-Kahoolawe-Maui-Big
Tropical storm watch for Maui County windward waters-Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island windward waters.
High surf advisory until 6 PM HST Tuesday for east facing shores
of The Big Island.