Flash Flood Warning 7, NWS Honolulu, HI

320 
WGHW70 PHFO 100208
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
408 PM HST Fri Sep 9 2022

HIC009-100315-
/O.CON.PHFO.FF.W.0007.000000T0000Z-220910T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maui HI-
408 PM HST Fri Sep 9 2022

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 515 PM HST THIS 
AFTERNOON FOR THE ISLAND OF MAUI IN MAUI COUNTY...

At 408 PM HST, radar indicated rainfall diminishing in coverage and 
intensity over west Maui. However, flooding from earlier rainfall 
continues. Maui Emergency Management Agency reports road closures in 
South Kihei.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Emergency management.

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...
  Kihei, Wailea, Ulupalakua, Makena and Keokea.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

LAT...LON 2077 15648 2078 15646 2079 15639 2062 15638
      2061 15644 2061 15645 2064 15647

FLASH FLOOD...OBSERVED

$$

BIRCHARD

226 
WGHW70 PHFO 100304
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
504 PM HST Fri Sep 9 2022

HIC009-100314-
/O.CAN.PHFO.FF.W.0007.000000T0000Z-220910T0315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maui HI-
504 PM HST Fri Sep 9 2022

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

The heavy rain has ended. Flash flooding is no longer expected to 
pose a threat. Some road closures may be ongoing in Kihei as flood 
waters gradually recede.

LAT...LON 2077 15648 2078 15646 2079 15639 2062 15638
      2061 15644 2061 15645 2064 15647

$$

BIRCHARD

Area Forecast Discussion
National Weather Service Honolulu HI
1000 AM HST Fri Sep 9 2022

.SYNOPSIS...
Moderate trade winds will weaken through Saturday, remain on the
lighter side through the weekend, then increase again early next
week. An area of increased moisture will bring clouds and showers to
mainly windward portions of the islands from Kauai to Maui into
tonight, with fewer showers Saturday and Sunday. However, the light
winds this weekend may allow some afternoon showers to develop over
leeward areas, with clearing at night. An increase in showers is
expected over the Big Island on Monday.

&&

.DISCUSSION...
An area of increased low-level moisture embedded within a moderate
trade wind flow continues to spread clouds and showers to the
islands from Maui to Kauai, largely bypassing the Big Island, where
skies are mostly sunny. Additionally, a developing trough aloft N of
Kauai has weakened and elevated the subsidence inversion, and latest
radar data indicates moisture extends as high as 14000', which has
allowed some of the showers to become briefly, although they are not
remaining over any one area for particularly long. We have received
several rainfall alarms this morning from gages in windward Kauai
and Oahu, with rainfall rates near 1 inch/hour observed. Although we
might normally expect some diurnal decrease in shower coverage this
afternoon, model guidance indicates weak low-level convergence
helping to support showery weather from Maui to Kauai into tonight
before moving W of the islands early Saturday.

Weak surface high pressure to the distant NE will dissipate
tomorrow, while a new high develops far N of the islands this
weekend. This new high will move slowly S toward the islands early
next week while gradually weakening. This will cause to trade winds
to gradually diminish through Saturday, then slowly strengthen
Sunday into next week. The gentle trade winds will remain strong
enough to bring showers to windward areas, especially during nights
and mornings, but will also be sufficiently light to allow land and
sea breezes over leeward areas. After the current field of moisture
clears the islands to the W on Saturday, some lingering low-level
moisture and weak instability associated with the trough aloft N of
Kauai will help support some shower development, especially over
Kauai and Oahu.

Global models continue to show a significant northward surge of
tropical moisture approaching the Big Island from the S, although
the timing has trended a little earlier, with PWAT increasing Sunday
night and Monday. Although this moisture field will likely be
weakening as it approaches, it looks as if it will bring an increase
in showers to the Big Island on Monday, especially windward.
Forecast grids will be modified to account for this change in
forecast philosophy. Moderate trade winds for the first part of next
week may trend weaker over the second half, and a nearby weak NE-SW
oriented low-level trough may bring an increase in showers around
midweek.

&&

.AVIATION...
Deeper low level moisture advecting into the islands from the east
has enhanced windward shower activity and cloud coverage. Periodic
MVFR ceilings and visibilities will continue through the rest of the
morning. AIRMET Sierra remains in effect for tempo mountain
obscuration for Maui, Molokai, Oahu, and Kauai, and will likely
remain in effect through midday.

Light to locally moderate trade winds will continue to gradually
weaken through Saturday as surface high pressure far northeast of
the state dissipates and is replaced by another high that will
slowly move towards the islands early next week. The result will be
light to locally moderate trades remaining strong enough to focus
showers and clouds across windward locations (especially during the
overnight through early morning hours), but weak enough to allow
nighttime land breezes and afternoon sea breezes for some leeward
locations.

&&

.MARINE...
Gentle to moderate east trade winds will generally remain in place
through this weekend as high pressure far off to the northeast of
the state weakens and relaxes the gradient down upon  the islands.
Lighter winds equate to just land and sea breezes along and near the
coasts through Sunday. Moderate to fresh trade winds will return
Monday and then hold through mid week.

The incoming south southwest swell will increase surf along south-
facing shores through the day Saturday, peaking out near surf
advisory levels late Sunday through Monday, then slowly fall through
mid week. A medium period southeast swell arriving Monday will be
added to the mix and will hang on through Wednesday. Surf along east-
facing shores will ease into the weekend as trades back off, but may
come up Sunday if a medium period easterly swell from former East
Pacific Hurricane Kay reaches our east shores. Choppy east wind wave
surf surf will pick up next week in response to strengthening trades.

&&

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

&&

DISCUSSION...Birchard
AVIATION...TS
MARINE...Blood