Alert archive / Hawaii / Flash Flood Warnings in 2021

Flash Flood Warning 25, NWS Honolulu, HI

March 11, 2021Honolulu County, Hawaii

NWS Honolulu, HI issued this flash flood warning at Mar 11, 2021, 4:15 PM 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: Mar 11, 2021, 4:15 PM HST (02:15 UTC)
Expired: Mar 11, 2021, 6:57 PM HST
In force: 3 hr
Issued by: NWS Honolulu, HI
Area: Storm-based polygon
Flood severity: None

County Honolulu County, HI

The radar

The Molokai radar (PHMO), 83 km from the middle of the area, began a volume at 02:15 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Lihue, (PHLI), launched 00:00Z, 2.3 hours before the alert went out and 161 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: 437 J/kg
Mixed-layer CIN: -23 J/kg
Mixed-layer LCL: 981 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 65 m²/s²
0-3 km storm-relative helicity: 60 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

731 
WGHW50 PHFO 120215
FFWHFO
HIC003-120515-
/O.NEW.PHFO.FF.W.0025.210312T0215Z-210312T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
415 PM HST Thu Mar 11 2021

The National Weather Service in Honolulu has issued a

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

* Until 715 PM HST.

* At 415 PM HST, radar indicated heavy rain and thunderstorms over 
  Wahiawa and Haleiwa with rainfall rates up to 3 inches per hour. A 
  line of rain and thunderstorms is moving towards Oahu from the 
  west, and is expected to move onshore within the hour. Flash 
  flooding is occurring or expected to begin shortly.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar indicated.

  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.

* This warning includes the entire island of Oahu.

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.

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

&&

This warning may need to be extended beyond 715 PM HST if flooding 
persists.

This Flash Flood Warning replaces the previously issued Flood 
Advisory that was in effect for The island of Oahu in Honolulu 
County.

LAT...LON 2158 15830 2160 15813 2173 15797 2155 15783
      2147 15783 2143 15779 2147 15778 2148 15774
      2145 15772 2141 15772 2131 15763 2125 15769
      2125 15772 2127 15772 2124 15782 2129 15787
      2131 15797 2129 15812 2148 15825 2153 15825

FLASH FLOOD...RADAR INDICATED

$$

M BALLARD

2 follow-up statements

186 
WGHW70 PHFO 120341
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
541 PM HST Thu Mar 11 2021

HIC003-120515-
/O.CON.PHFO.FF.W.0025.000000T0000Z-210312T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Honolulu HI-
541 PM HST Thu Mar 11 2021

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 715 PM HST THIS 
EVENING FOR THE ISLAND OF OAHU IN HONOLULU COUNTY...

At 541 PM HST, radar indicated heavy showers near Pearl City with 
rainfall rates up to 2 inches per hour. A line of rain and 
thunderstorms is moving onshore near Kaena Point and is expected to 
spread across the island shortly. Flash flooding is occurring or 
expected to begin shortly.

HAZARD...Flash flooding caused by heavy rain.

SOURCE...Radar indicated.

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.

This warning includes the entire island of Oahu.

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.

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

&&

This warning may need to be extended beyond 715 PM HST if flooding 
persists.

LAT...LON 2158 15830 2160 15813 2173 15797 2155 15783
      2147 15783 2143 15779 2147 15778 2148 15774
      2145 15772 2141 15772 2131 15763 2125 15769
      2125 15772 2127 15772 2124 15782 2129 15787
      2131 15797 2129 15812 2148 15825 2153 15825

FLASH FLOOD...RADAR INDICATED

$$

M BALLARD

037 
WGHW70 PHFO 120457
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
657 PM HST Thu Mar 11 2021

HIC003-120507-
/O.CAN.PHFO.FF.W.0025.000000T0000Z-210312T0515Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Honolulu HI-
657 PM HST Thu Mar 11 2021

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

The heavy rain has diminished and flooding is no longer expected to 
pose a threat. Moderate showers continue to affect portions of the 
island however and some minor ponding of water on roadways can be 
expected.

A Flash Flood Watch remains in effect until 600 PM HST Friday.

LAT...LON 2158 15830 2160 15813 2173 15797 2155 15783
      2147 15783 2143 15779 2147 15778 2148 15774
      2145 15772 2141 15772 2131 15763 2125 15769
      2125 15772 2127 15772 2124 15782 2129 15787
      2131 15797 2129 15812 2148 15825 2153 15825

$$

JELSEMA

The office that day

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

Issued	Product	Office	Counties	Lasted
Mar 11, 2:22 PM HST	Flash Flood Warning	HFO	Honolulu	2 hr
Mar 11, 2:46 PM HST	Areal Flood Advisory	HFO	Kalawao	3 hr
Mar 11, 3:22 PM HST	Special Marine Warning	HFO		22 min
Mar 11, 6:09 PM HST	Areal Flood Advisory	HFO	Hawaii	99 min
Mar 11, 7:35 PM HST	Areal Flood Advisory	HFO	Honolulu	81 min
Mar 11, 8:54 PM HST	Areal Flood Advisory	HFO	Kalawao	6 hr
Mar 12, 12:23 AM HST	Special Marine Warning	HFO		112 min
Mar 12, 2:42 AM HST	Areal Flood Advisory	HFO	Kauai	2 hr
Mar 12, 3:56 AM HST	Small Craft Advisory	HFO		10 days
Mar 12, 5:04 AM HST	Flash Flood Warning	HFO	Kauai	2 hr
Mar 12, 5:29 AM HST	Areal Flood Advisory	HFO	Honolulu	2 hr
Mar 12, 8:49 AM HST	Special Marine Warning	HFO		41 min
Mar 12, 8:51 AM HST	Areal Flood Advisory	HFO	Kauai	2 hr
Mar 12, 9:45 AM HST	Gale Warning	HFO		6 hr
Mar 12, 11:02 AM HST	Flash Flood Warning Considerable damage threat	HFO	Kauai	3 hr
Mar 12, 11:22 AM HST	Areal Flood Advisory	HFO	Honolulu	68 min
Mar 12, 1:39 PM HST	Flash Flood Warning Considerable damage threat	HFO	Kauai	6 hr

Nearby

Flash Flood Warnings in Hawaii, 2021 Every flash flood warning in 2021

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; radar from the NEXRAD Level II archive.