131 
FXHW60 PHFO 150213
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
413 PM HST Wed Feb 14 2018

.SYNOPSIS...
A trough, at the surface and aloft, will persist near the islands through
at least the beginning of next week. The trough will bring muggy, rainy
weather. A front over Molokai will move slowly east through Friday
night with drier weather over Kauai and Oahu and wetter weather for
Maui County and the Big Island. Over the weekend, the rain band may
spread back west over Oahu and possibly Kauai.

&&

.DISCUSSION...
Satellite loops show a low about 560 miles northwest of Oahu with
a trough extending from the low to near Kauai. Winds near the 
surface are from the southeast near the Big Island of Hawaii, 
veering to southwest near Kauai. The low is making the atmosphere
over the islands unstable while very moist air is moving up over
the area from the southeast.

A front over Molokai is moving southeast slowly. There is a band
of heavy showers and isolated thunderstorms along the front. One 
shower after another is moving along the band from the south 
southwest producing heavy rain over Molokai. Behind the front,
shallow gentle west winds have brought drier weather to Oahu and
Kauai. Ahead of the front, the weather is relatively quiet on the
Big Island of Hawaii, with cloudy skies over the lower slopes but
only light rainfall. The shower band over Molokai is expected to 
continue moving slowly southeast across Maui County tonight and 
over the Big Island by tomorrow. A Flash Flood Watch is in effect
for Maui County and the Big Island for heavy rainfall from the
front. The Band may linger over the Big Island through the
weekend. Temperatures will be cooling aloft by the weekend, so 
chances of snow on the summits of Mauna Kea and Mauna Loa will 
increase.

The forecast becomes more uncertain beyond the weekend, but the global
models suggest a new low will form northwest of the area and move toward
the islands early next week. As the new low approaches, the shower band
may spread back westward. By the middle of next week, a ridge may build
northeast of the islands with trade winds possibly returning for the
second half of next week.

$$

.MARINE...
Winds should be on the decline this evening over the eastern 
half of the coastal waters, as the front weakens and pushes E, 
weakening the pressure gradient near Maui county and the Big 
Island. Did not get a good mid-morning ASCAT pass but based on 
the downward trend in the guidance this evening, will cancel the 
Small Craft Advisory at 4 pm. A general trend toward weakening 
winds (especially over the eastern half of the coastal waters) is
expected over the next day or so as a weak front or surface 
trough shifts toward Maui and the Big Island for Thu into Fri. The
trough should weaken enough over the weekend for northerlies to
increase near the Kauai waters and southeasterlies to increase
over the eastern waters.

Seas will also continue to decline as the quick WNW swell pulse
fades. A storm-force low pressure approaching the dateline at 48N
will only briefly have a short fetch window aimed at us, providing
as us sub-advisory level NW pulse this weekend. A very large 
surface high far to our NE, with 15-25 kt trades over a wide fetch
over the eastern Pacific, will keep short period surf going on 
eastern shores for the next few days.

Instability and deep layer shear appear to be more than sufficient
through the next 12 to 24 hours for some thunderstorms to become 
strong to severe, especially over the coastal waters N of Maui 
county and the Big Island, extending out into the adjacent 
offshore waters.

&&

AVIATION...
A cold front over Molokai is slowly pushing SE with a low 
pressure center well to the NW of the island chain. The low will 
push to the SE then shift to the east on Thursday morning 
remaining a few hundred miles north of Kauai. Shower activity 
associated with the front has a history of embedded heavy rain and
thunderstorms. This is now tracking across Molokai and should 
affect Lanai this afternoon and Maui later this afternoon into the
evening hours. Layered clouds associated with this cloud band has
the potential for light ice. Periods of MVFR to IFR conditions 
can be expected with the embedded heavier rain. AIRMET SIERRA for 
MTN OBSC is posted over Oahu and Molokai and may need to be 
expanded over Maui tonight. A trough aloft is producing some 
turbulence, so AIRMET TANGO is in effect for moderate turbulence 
aloft.

&& 

$$
DISCUSSION...Donaldson
MARINE...R Ballard
AVIATION...Chevalier/Eaton

750 
FXHW60 PHFO 150316 CCA
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
413 PM HST Wed Feb 14 2018

.SYNOPSIS...
A trough, at the surface and aloft, will persist near the islands 
through at least the beginning of next week. The trough will bring 
muggy, rainy weather. A front over Molokai will move slowly east 
through Friday night with drier weather over Kauai and Oahu and 
wetter weather for Maui County and the Big Island. Over the weekend, 
the rain band may spread back west over Oahu and possibly Kauai.

&&

.DISCUSSION...
Satellite loops show a low about 560 miles northwest of Oahu with a 
trough extending from the low to near Kauai. Winds near the surface 
are from the southeast near the Big Island of Hawaii, veering to 
southwest near Kauai. The low is making the atmosphere over the 
islands unstable while very moist air is moving up over the area 
from the southeast.

A front over Molokai is moving southeast slowly. There is a band of 
heavy showers and isolated thunderstorms along the front. One shower 
after another is moving along the band from the south southwest 
producing heavy rain over Molokai. Behind the front, shallow gentle 
west winds have brought drier weather to Oahu and Kauai. Ahead of 
the front, the weather is relatively quiet on the Big Island of 
Hawaii, with cloudy skies over the lower slopes but only light 
rainfall. The shower band over Molokai is expected to continue 
moving slowly southeast across Maui County tonight and over the Big 
Island by tomorrow. A Flash Flood Watch is in effect for Maui County 
and the Big Island for heavy rainfall from the front. The Band may 
linger over the Big Island through the weekend. Temperatures will be 
cooling aloft by the weekend, so chances of snow on the summits of 
Mauna Kea and Mauna Loa will increase.

The forecast becomes more uncertain beyond the weekend, but the 
global models suggest a new low will form northwest of the area and 
move toward the islands early next week. As the new low approaches, 
the shower band may spread back westward. By the middle of next 
week, a ridge may build northeast of the islands with trade winds 
possibly returning for the second half of next week.

&&

.MARINE...
Winds should be on the decline this evening over the eastern 
half of the coastal waters, as the front weakens and pushes E, 
weakening the pressure gradient near Maui county and the Big 
Island. Did not get a good mid-morning ASCAT pass but based on 
the downward trend in the guidance this evening, will cancel the 
Small Craft Advisory at 4 pm. A general trend toward weakening 
winds (especially over the eastern half of the coastal waters) is
expected over the next day or so as a weak front or surface 
trough shifts toward Maui and the Big Island for Thu into Fri. The
trough should weaken enough over the weekend for northerlies to
increase near the Kauai waters and southeasterlies to increase
over the eastern waters.

Seas will also continue to decline as the quick WNW swell pulse
fades. A storm-force low pressure approaching the dateline at 48N
will only briefly have a short fetch window aimed at us, providing
as us sub-advisory level NW pulse this weekend. A very large 
surface high far to our NE, with 15-25 kt trades over a wide fetch
over the eastern Pacific, will keep short period surf going on 
eastern shores for the next few days.

Instability and deep layer shear appear to be more than sufficient
through the next 12 to 24 hours for some thunderstorms to become 
strong to severe, especially over the coastal waters N of Maui 
county and the Big Island, extending out into the adjacent 
offshore waters.

&&

AVIATION...
A cold front over Molokai is slowly pushing SE with a low 
pressure center well to the NW of the island chain. The low will 
push to the SE then shift to the east on Thursday morning 
remaining a few hundred miles north of Kauai. Shower activity 
associated with the front has a history of embedded heavy rain and
thunderstorms. This is now tracking across Molokai and should 
affect Lanai this afternoon and Maui later this afternoon into the
evening hours. Layered clouds associated with this cloud band has
the potential for light ice. Periods of MVFR to IFR conditions 
can be expected with the embedded heavier rain. AIRMET SIERRA for 
MTN OBSC is posted over Oahu and Molokai and may need to be 
expanded over Maui tonight. A trough aloft is producing some 
turbulence, so AIRMET TANGO is in effect for moderate turbulence 
aloft.

&& 

$$
DISCUSSION...Donaldson
MARINE...R Ballard
AVIATION...Chevalier/Eaton