700 
FXHW60 PHFO 101957
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
957 AM HST Sun Feb 10 2019

.SYNOPSIS...
A powerful storm system will pass by just north of the islands
today and tonight. This will result in large, destructive surf, 
locally damaging winds, and periods of squally showers across most
of the state. Unsettled weather may persist into the middle of 
next week as the storm lingers to the northeast of the state, with
a more typical trade wind weather pattern developing later in the
week.

&&

.DISCUSSION...
Satellite imagery shows the center of a powerful low pressure 
system is currently located about 120 miles north of Kauai. The 
system is moving steadily toward the south southeast at the 
present time. Bands of showers are moving across the area from 
west to east with some showers being briefly heavy. Very windy 
conditions are being reported at many stations with strong gusts 
occurring at times especially in rain squalls. A High Wind Warning
is in effect for the entire area. Snow has been reported over the
summit area of Haleakala so a Winter Weather Advisory is in 
effect. As some of the precipitation moves westward today, winter 
weather is also possible over the higher terrain on the Big Island
as well. A few thunderstorms are also a possibility across the 
area today but most should remain just north of the state. 

The low will pass by just north of the state later today and 
tonight. Winds will lower gradually from west to east across most 
areas tonight but will likely remain rather windy over and downslope
from higher terrain, and where winds are most efficiently funneled
around terrain and through valleys. Winds over the summits will 
remain very windy as well. A bit drier airmass will fill in behind
the low but passing showers can still be expected especially over
north facing slopes. Winter weather may also continue over the
high summits on Maui and the Big Island. 

Monday through Wednesday, the surface low is expected to longer 
northeast of the area Monday and Tuesday while gradually 
weakening, then slowly lift out to the northeast on Wednesday. 
Breezy to locally windy north to northwest winds will linger on 
Monday then become more northerly then northeasterly by Wednesday
with speeds expected to be just a bit lighter. The upper trough 
is expected to linger across the area keeping the airmass a bit 
unstable. Moisture rotating around the low as well as moisture 
embedded within the low level wind flow will bring periods of 
showers to windward and mauka areas with some showers also 
expected over leeward locations. 

Thursday through Saturday, the global models have some 
similarities and some differences between. On Thursday both 
models keep strong high pressure far north of the area with a 
weakening area of low pressure off to the east northeast of the 
state. Upper troughing is also expected to linger across the 
area. Breezy to locally windy northeast winds can be expected 
Wednesday and Thursday with winds expected to drop off a bit as we
head into next weekend. The upper troughing will keep things a 
bit showery over windward and mauka areas with the winds 
sufficiently strong enough to blow some passing showers over to 
select leeward areas at times. Some differences do show up in the 
lower levels as we head into next weekend. The GFS shows a weak 
trough lingering several hundred miles east of the Big Island 
while the ECMWF shows a stronger trough or a weak low just a few 
hundred miles east northeast of the Big Island. Winds will remain 
out of the northeast but could become lighter if the ECMWF model 
pans out. 

&&

.AVIATION...
A storm low has moved to a position about 120 statute miles N of 
Kauai and has begun moving toward the southeast. The tight 
pressure gradient associated with this deep low will generate very
strong winds across the area, mainly from the west and northwest 
today and tonight. Passing showers, with a slight chance of 
thunderstorms, will also affect the isles, bringing brief to TEMPO
MVFR conditions with lower ceilings and visibilities.

AIRMETs are currently in effect for mountain obscuration, strong
surface winds in excess of 30 kt, moderate low-level and upper- 
level turbulence. As the low gets closer to the islands, 
turbulence will likely increase at all levels. SIGMETs may be 
issued, if warranted, for greater than moderate turbulence.

&&

.MARINE...
Life-threatening conditions will continue over all Hawaiian waters 
through Monday morning. If experienced mariners in properly equipped 
vessels are considering venturing away from protected waters today 
or tonight, prepare for gale force winds, treacherous seas, and 
periods of storm force wind gusts in squalls. If in doubt, DO NOT GO 
OUT!

The latest satellite imagery showed this storm-force low tracking 
south-southeast around 100 nm north of Kauai this morning. As 
this system makes a turn toward the east and skirts the northern 
waters this afternoon/evening, winds will gradually veer from the 
west to the north-northwest. Seas are forecast to peak later this 
afternoon through this evening as the system makes its closest 
point of approach. Recent altimeter data showed peak seas up to 38
ft a few hundred nautical miles north-northwest of Kauai within 
the pocket of storm-force northerly winds on the west side of the 
low. The nearshore PacIOOS buoys are reporting seas ranging from 
15 ft at Pauwela to 26 ft at Hanalei this morning, which will 
quickly climb into the 20 to 35 ft range later today at the peak 
of the event.

A combination of gale-force winds and unusually high seas that 
continue to batter the coasts has led to life-threatening surf along 
exposed coasts. The duration of this event will result in 
significant beach erosion that could result in property damage along 
the immediate north and west facing shores. Overwash onto vulnerable 
roadways will remain possible through tonight, especially at and 
around the high tide cycles. Strong currents and surges in the 
exposed harbors will be capable of damaging boats and infrastructure 
due to the jostling of docks. Surf along south facing shores has 
also quickly come up this morning due to the westerly winds and will 
near advisory levels by this afternoon. 

Guidance depicts this area of low pressure slowly tracking northeast 
and away from the islands through the first half of the week. Winds 
are forecast to shift out of the northeast and trend down into the 
fresh to strong category Monday night through Tuesday locally. 
Strong pressure gradient between this low and strong high pressure
far north of the area, however, will continue to generate large 
seas out of the northeast. Small craft advisory seas and high surf
for exposed north and east facing shores will result through the 
week. Overwash onto vulnerable roadways and significant beach 
erosion will become a possibility Wednesday through the second 
half of the week, especially in the more vulnerable locations, 
such as Hilo. 

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 6 AM HST Monday for Niihau-Kauai-Oahu-
Molokai-Lanai-Kahoolawe-Maui-Kona-South Big Island-Big Island 
North and East-Kohala-Big Island Interior.

High Surf Warning until 6 AM HST Monday for Niihau-Kauai 
Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu 
Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley-
Windward Haleakala.

High Surf Warning from 4 PM this afternoon to 6 AM HST Monday 
for Kona-Kohala.

High Surf Advisory from 4 PM this afternoon to 6 AM HST Monday 
for Big Island North and East.

High Surf Advisory from noon today to 6 AM HST Monday for Lanai 
Makai-Kahoolawe-Maui Leeward West-Leeward Haleakala.

High Wind Warning until 6 PM HST Monday for Big Island Summits.

Winter Weather Advisory until 6 PM HST this evening for 
Haleakala Summit.

Gale Warning until 6 AM HST Monday for all Hawaiian waters-

&&

$$

DISCUSSION...Burke
AVIATION...Kinel
MARINE...Gibbs