Flash Flood Warning 9, NWS Honolulu, HI

932 
WGHW50 PHFO 180755
FFWHFO
HIC009-181115-
/O.EXT.PHFO.FF.W.0009.000000T0000Z-221118T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
955 PM HST Thu Nov 17 2022

The National Weather Service in Honolulu has extended the

* Flash Flood Warning for...
  The island of Maui in Maui County

* Until 115 AM HST.

* At 955 PM HST, radar indicated heavy rain continuing over windward 
  portions of east Maui. Rain was falling at a rate of 1 to 3 inches 
  per hour. Flash flooding is ongoing.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar.

  IMPACT...Flooding in drainages, streams, rivers, roads,
           properties, and other low-lying areas. Public road
           closures possible in some areas. Landslides are
           possible in steep terrain.

* Some locations that will experience flash flooding include...
  Kipahulu, Nahiku, Hana, Kaupo, Keanae, Haleakala National Park, 
  Wailua and Hamoa.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

The heavy rains may cause rock and mudslides in steep terrain areas.

Stay away from streams, rivers, drainage ditches, and culverts, even 
if they are currently dry.

Do not cross fast flowing or rising water in your vehicle, or on 
foot. Turn around, don't drown.

&&

This warning may need to be extended beyond 115 AM HST if flooding 
persists.

LAT...LON 2060 15624 2066 15624 2070 15613 2076 15611
      2084 15624 2092 15620 2087 15614 2088 15613
      2087 15612 2086 15612 2085 15612 2084 15611
      2081 15600 2078 15597 2077 15597 2070 15598
      2064 15604 2061 15614 2062 15619

FLASH FLOOD...RADAR INDICATED

$$

POWELL

756 
WGHW70 PHFO 180938
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
1138 PM HST Thu Nov 17 2022

HIC009-180948-
/O.CAN.PHFO.FF.W.0009.000000T0000Z-221118T1115Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maui HI-
1138 PM HST Thu Nov 17 2022

...FLASH FLOOD WARNING IS CANCELLED FOR THE ISLAND OF MAUI IN MAUI 
COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat.

LAT...LON 2060 15624 2066 15624 2070 15613 2076 15611
      2084 15624 2092 15620 2087 15614 2088 15613
      2087 15612 2086 15612 2085 15612 2084 15611
      2081 15600 2078 15597 2077 15597 2070 15598
      2064 15604 2061 15614 2062 15619

$$

POWELL

Area Forecast Discussion
National Weather Service Honolulu HI
358 PM HST Thu Nov 17 2022

.SYNOPSIS...
A surface trough near the islands weakened the trades today,
allowing some afternoon clouds and showers over interior and
leeward locales. An upper trough will enhance trade wind showers
into Friday, making thunderstorms possible north and east of Oahu
and Maui County through tonight. Winds will become strong this
weekend as the upper trough exits and high pressure redevelops
northeast of the islands.

&&

.DISCUSSION...
Current visible satellite and radar imagery shows scattered heavy
showers and a few lightning strikes over the windward Oahu and
Molokai coastal waters, where a mid-level shortwave moving
eastward is meeting a surface trough moving slowly westward.
Thunderstorms continue to develop just outside the coastal waters
to the north of Maui County, as well, along the leading edge of
the shortwave. The surface trough has also served to weaken winds
over the local area today, allowing some low clouds and showers to
develop over interior and leeward locations of most islands.
Thunder has been absent from interior Big Island so far today, but
some cells are starting to pop there, so a slight chance remains
into this evening.

As the shortwave and surface trough near each other tonight, the
surface trough will become sharper and further enhance showers,
with some heavy at times into Friday. As the surface trough
interacts with the instability associated with the shortwave
through tonight, isolated thunderstorms could develop in the area
to the north and east of Oahu and Maui County. The surface trough
northeast of the state will also keep winds in the light to
moderate range through Friday morning.

As the trough aloft exits the area to the east, the surface trough
washes out, allowing trade winds to return by Friday afternoon.
The weak surface ridge to the north of the area will restrengthen
into a high to the northeast this weekend, causing trades to
become strong over the state through early next week. During this
time, building mid-level ridging and below normal precipitable
water values will result in a drier than average trade shower
pattern.

In the long range, the global models are hinting at a front
approaching Hawaii from the northwest beginning Wednesday night.
As we head into Thanksgiving Day, a band of showers and large area
of strong northeast winds behind the front could move into the
island chain. Quite a bit of variance exists in the models this
far out, so the forecast for that period is a blend of the current
forecast with the latest deterministic models and their respective
ensembles.

&&

.AVIATION...
A surface trough moving slowly westward, north of the islands,
will maintain a weakened background trade wind flow across the
state into Friday. An upper trough moving toward Kauai, will
slowly move eastward across the islands through the forecast
period, enhancing atmospheric instability across the state. A more
typical trade wind flow is expected to redevelop later Friday, as
the surface ridge becomes reestablished north of the state.
Overall, showers will remain scattered across much of the region
tonight, with locally heavy rainfall possible. Showers will then
tend to favor windward zones later Friday as a more typical trade
wind weather pattern develops. In addition, there is a slight
chance of thunderstorms for some areas tonight.

Mainly VFR conditions are expected across TAF locations through
the period, however MVFR conditions are expected in heavier
showers, though the areal extent should remain below AIRMET
criteria.

A period of light ice could potentially develop in a layer
btw FL180/FL280 through tonight, as a band of mid and upper lvl
moisture lifts up across the islands.

&&

.MARINE...
A surface ridge about 200 nm N of Kauai is supporting light to
moderate trade winds on the large scale, but a surface trough near
and north of Maui and Oahu continues to interrupt the trade flow
near the islands. Light to moderate E-SE winds prevail E of the
trough axis, moderate NE-E winds are W of the trough axis, and
light winds exist along the axis of the trough. Heavy showers and
isolated thunderstorms are forming near the trough axis this
afternoon, with greatest coverage over Oahu's windward waters.

Little overall change is expected this evening as the trough
gradually drifts toward the N. As high pressure builds to the NW
of the islands and the trough gradually weakens through Friday, NE
winds will increase statewide, beginning over Kauai waters as
early as tonight. As the high builds through the weekend, strong
ENE trade winds are expected to drive increased seas, with Small
Craft Advisory (SCA) thresholds for winds/seas being exceeded in
many areas, potentially as early as Friday in the windier zones.
Some weakening of the ridge will likely lead to gradually
diminishing wind speeds and seas early next week.

A fresh pulse of NNW swell (340 degrees) that arrived today is
expected to peak soon, then gradually lower into Friday. A High
Surf Advisory (HSA) is posted for N facing shores of all islands
except Lanai and Kahoolawe. The source of this swell was a low
that directed largest seas to the NE of the islands, thus NDBC
buoys 51001/51101 NW of Kauai are not detecting the bulk of this
swell energy, with buoy 51000 being more representative of what
has been detected by near shore PacIOOS buoys. This swell will
gradually diminish Friday and Saturday. A new long-period WNW
swell will build Saturday night and Sunday, producing surf near
HSA levels as it peaks Sunday night and Monday, then slowly lower
through the middle of next week. Another NNW swell is possible
around the middle of next week.

East shore surf will remain small through Friday, but will be
increasing over the weekend and early next week as trade winds
strengthen. A small S swell now arriving will gradually diminish
over the weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Friday for north facing shores
of Niihau, Kauai, Oahu, Molokai, Maui, and the Big Island.

&&

DISCUSSION...TS/RAB
AVIATION...SWR
MARINE...Birchard