Alert archive / Hawaii / Flash Flood Warnings in 2023

Flash Flood Warning 21, NWS Honolulu, HI

April 29, 2023Honolulu County, Hawaii

NWS Honolulu, HI issued this flash flood warning at Apr 29, 2023, 4:58 AM HST for Honolulu County, Hawaii. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Apr 29, 2023, 4:58 AM HST (14:58 UTC)
Expired: Apr 29, 2023, 8:00 AM HST
In force: 3 hr
Issued by: NWS Honolulu, HI
Area: Storm-based polygon
Flood severity: None

County Honolulu County, HI

The nearest sounding before it

Lihue, (PHLI), launched 12:00Z, 3.0 hours before the alert went out and 166 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1582 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 604 m above ground
0-6 km bulk shear: 4 kt
0-1 km storm-relative helicity: 2 m²/s²
0-3 km storm-relative helicity: 8 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

540 
WGHW50 PHFO 291458
FFWHFO
HIC003-291800-
/O.NEW.PHFO.FF.W.0021.230429T1458Z-230429T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
458 AM HST Sat Apr 29 2023

The National Weather Service in Honolulu has issued a

* Flash Flood Warning for...
  The island of Oahu in Honolulu County

* Until 800 AM HST.

* At 458 AM HST, the Waikane stream reported a rapid rise in water 
  level, and has reached a level that can lead to the closure of 
  Kamehameha Highway due to water over the roadway. Flooding is 
  occurring in Waikane Stream and other nearby drainages.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Stream Gauges.

  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...
  Waikane, Waiahole, Kahaluu, Kaaawa, Ahuimanu, Punaluu, Pearl City, 
  Mililani, Aiea, Hauula, Wahiawa, Halawa, Moanalua, Kaneohe, Salt 
  Lake, Laie, Kaneohe Marine Base, Kalihi, Maunawili and Kahuku.

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.

&&

This warning may need to be extended beyond 800 AM HST if flooding 
persists.

LAT...LON 2160 15812 2173 15800 2173 15798 2155 15783
      2147 15783 2143 15779 2144 15778 2146 15779
      2147 15778 2147 15771 2141 15773 2134 15768
      2133 15765 2129 15776 2137 15792

FLASH FLOOD...GAUGE INDICATED

$$

JELSEMA

3 follow-up statements

295 
WGHW70 PHFO 291531
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
531 AM HST Sat Apr 29 2023

HIC003-291800-
/O.CON.PHFO.FF.W.0021.000000T0000Z-230429T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Honolulu HI-
531 AM HST Sat Apr 29 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 AM HST THIS MORNING 
FOR THE ISLAND OF OAHU IN HONOLULU COUNTY...

At 531 AM HST, local law enforcement reported heavy rain over 
windward Oahu. Rain was falling at a rate of 1 to 2 inches per hour. 
Flash flooding is ongoing and Kamehameha Highway has been closed in 
both directions due to water over the road between 48-279 Kamehameha 
Highway and Waikane Valley Road.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Law enforcement.

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...
  Waikane, Waiahole, Kahaluu, Kaaawa, Ahuimanu, Punaluu, Pearl City, 
  Mililani, Aiea, Hauula, Wahiawa, Halawa, Moanalua, Kaneohe, Salt 
  Lake, Laie, Kaneohe Marine Base, Kalihi, Maunawili and Kahuku.

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 2160 15812 2173 15800 2173 15798 2155 15783
      2147 15783 2143 15779 2144 15778 2146 15779
      2147 15778 2147 15771 2141 15773 2134 15768
      2133 15765 2129 15776 2137 15792

FLASH FLOOD...OBSERVED

$$

JELSEMA

286 
WGHW70 PHFO 291703
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
703 AM HST Sat Apr 29 2023

HIC003-291800-
/O.CON.PHFO.FF.W.0021.000000T0000Z-230429T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Honolulu HI-
703 AM HST Sat Apr 29 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 8 AM HST THIS MORNING 
FOR THE ISLAND OF OAHU IN HONOLULU COUNTY...

At 703 AM HST, radar indicated that the areal coverage of the 
heaviest rainfall continued to diminish this morning. Radar showed 
rainfall rates around 1 inch per hour, locally up to 2 inches per 
hour, now with the showers moving over windward Oahu this morning. 
Gauges on the Kaluanui, Punaluu and Waikane Streams show stream 
flows have peaked and continue to trend downward as rainfall rates 
diminish.

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...
  Waikane, Waiahole, Kahaluu, Kaaawa, Ahuimanu, Punaluu, Pearl City, 
  Mililani, Aiea, Hauula, Wahiawa, Halawa, Moanalua, Kaneohe, Salt 
  Lake, Laie, Kaneohe Marine Base, Kalihi, Maunawili and Kahuku.

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 2160 15812 2173 15800 2173 15798 2155 15783
      2147 15783 2143 15779 2144 15778 2146 15779
      2147 15778 2147 15771 2141 15773 2134 15768
      2133 15765 2129 15776 2137 15792

FLASH FLOOD...RADAR INDICATED

$$

SWR

882 
WGHW70 PHFO 291757
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
757 AM HST Sat Apr 29 2023

HIC003-291807-
/O.EXP.PHFO.FF.W.0021.000000T0000Z-230429T1800Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Honolulu HI-
757 AM HST Sat Apr 29 2023

...FLASH FLOOD WARNING WILL EXPIRE AT 8 AM HST THIS MORNING FOR THE 
ISLAND OF OAHU IN HONOLULU COUNTY...

Heaviest rainfall from earlier this morning has ended allowing flood 
waters on area streams to continue to recede.

LAT...LON 2160 15812 2173 15800 2173 15798 2155 15783
      2147 15783 2143 15779 2144 15778 2146 15779
      2147 15778 2147 15771 2141 15773 2134 15768
      2133 15765 2129 15776 2137 15792

$$

SWR

The office that day

Everything else NWS Honolulu, HI issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 28, 2:58 PM HST	Areal Flood Advisory	HFO	Hawaii	4 hr
Apr 29, 3:23 AM HST	Small Craft Advisory	HFO		60 hr
Apr 29, 3:34 AM HST	Areal Flood Advisory	HFO	Honolulu	84 min
Apr 29, 5:02 AM HST	Areal Flood Advisory	HFO	Kalawao	3 hr

Nearby

Flash Flood Warnings in Hawaii, 2023 Every flash flood warning in 2023

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.