Small Craft Advisory 40, NWS Honolulu, HI

Area Forecast Discussion
National Weather Service Honolulu HI
902 PM HST Thu Nov 8 2018

.SYNOPSIS...
A shear line northwest of Kauai will move over Kauai Friday
morning and push south of the Big Island on Sunday. A new high
will build east behind the front.

&&

.DISCUSSION...
The latest surface analysis shows a 1032 mb surface high centered far
northeast of the area near 44N 135W with a ridge extending to about
200 miles northeast of the islands. The ridge is producing gentle to
moderate east northeast winds over the main Hawaiian Islands. The
ridge will move northeast and erode from the west over the next
few days. A poorly defined northeast to southwest shear line lies
150 miles northwest of Kauai. The shear line marks the boundary
between weaker east northwest winds southeast of the shear line
and stronger northeast winds northwest of the shearline. There are
some showers along the line, but the shower band is currently
rather diffuse.

A surface trough approaching from the southeast has merged with a
trough that developed over the islands ahead of the approaching shear
line. There is a large area of layered clouds and embedded thunderstorms
southeast of the Big Island associated with this trough. The GFS
and ECMWF show these clouds and showers remaining east of the
Hawaiian Islands.

Locally heavy showers that formed over the islands during the afternoon
due to afternoon heating have subsided, but some showers will move
over the islands tonight in the east northeast low level flow.

Showery low clouds ahead of the shear line are expected to reach
Kauai tomorrow morning. These showers will move across Oahu Friday
night, across Maui County on Saturday and across the Big Island
of Hawaii Saturday afternoon through Sunday morning. Locally
strong north northeast winds will spread over the islands behind
the shear line. There will be cooler, drier air behind the
shearline, so rainfall will subside. Differences remain between
the GFS and ECMWF with the timing of the shear line and our
forecasts may need to be updated to reflect changes in timing.

A surface high will build east behind the shear line. Early next
week winds will shift out of the northeast. As the winds shift to
a more- typical northeasterly trade-wind direction, showers will
be focused over mainly windward areas with mostly dry weather over
leeward areas. By the middle of next week as the high moves away
to the northeast. Winds will weaken and increasing moisture may
bring an uptick in showers during the second half of the coming
week, but it is too early to be very confident about that.

&&

.AVIATION...
VFR conditions to prevail overnight. East northeast winds will
push a few showers over east sections this evening. Offshore land
breezes will develop and help keep the showers offshore later
tonight.

A shear line will reach Kauai about mid-morning Friday. Expect
MVFR conditions to accompany the shear line. The shear line will
continue moving southeast, reaching Oahu Friday evening.

&&

.MARINE...
Fresh to strong northerly winds are expected to fill in across the
Kauai and Oahu waters through the day Friday, then across the rest
of the state Friday night through the weekend as a shear line
moves down the island chain. Seas will respond and reach advisory
levels over the northwest Kauai waters as early as Friday afternoon,
then across most waters by Saturday. As a result, a small craft
advisory will be issued for most waters later tonight to account
for winds and seas, which will likely continue through a good
portion of the weekend. Winds will shift to a more typical trade
wind direction Sunday night into early next week, potentially
holding in the fresh to strong category as a ridge of high
pressure noses southeast over the state.

There will be a series of N to NNW swells impacting the islands
through next week. The current NNW swell is expected to hold
through Friday. A larger short to mid period N swell is expected
to move in Friday and may bring near advisory surf to north
facing shores over the weekend. As this swell slowly fades in the
ensuing days, a small NW swell with a 15 second period will reach
our shores on Monday. A larger NNW swell will be possible Tuesday
that may warrant another high surf advisory for at least the north
facing shores.

A small south-southwest swell is providing a slight increase in
surf across south facing shores today. A larger and very long
period southwest swell is expected to fill in late Friday, peak
Saturday at heights around the summer average and gradually
decline early next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

DISCUSSION...Donaldson
AVIATION...Lau
MARINE...Gibbs

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HONOLULU HI
1031 PM HST THU NOV 8 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1029 PM     FLASH FLOOD      WAIKANE                 21.50N 157.88W
11/08/2018                   HONOLULU           HI   LAW ENFORCEMENT

            ROAD CLOSED BETWEEN WAIKANE AND WAIAHOLE DUE TO HEAVY
            RAINFALL AND ELEVATED STREAMS.

&&

JGIBBS