Alert archive / Hawaii / Flash Flood Warnings in 2021

Flash Flood Warning 48, NWS Honolulu, HI

December 17, 2021Kalawao County, Hawaii

NWS Honolulu, HI issued this flash flood warning at Dec 17, 2021, 2:39 PM HST for Kalawao County, Hawaii. It was in force for 66 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Dec 17, 2021, 2:39 PM HST (00:39 UTC)
Expired: Dec 17, 2021, 3:45 PM HST
In force: 66 min
Issued by: NWS Honolulu, HI
Area: Storm-based polygon
Flood severity: None

County Kalawao County, HI

The radar

The Molokai radar (PHMO), 90 km from the middle of the area, began a volume at 00:41 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

Hilo, (PITO), launched 00:00Z, 0.7 hours before the alert went out and 189 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: 911 J/kg
Mixed-layer CIN: -19 J/kg
Mixed-layer LCL: 847 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: -20 m²/s²
0-3 km storm-relative helicity: 26 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

941 
WGHW50 PHFO 180039
FFWHFO
HIC009-180345-
/O.NEW.PHFO.FF.W.0048.211218T0039Z-211218T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
239 PM HST Fri Dec 17 2021

The National Weather Service in Honolulu has issued a

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

* Until 545 PM HST.

* At 239 PM HST, radar indicated heavy rain over west Haleakala 
  slopes and across the west Maui mountains. Additional showers are 
  beginning to develop across other areas on Maui. Rain was falling 
  at a rate of 3 to 4 inches per hour in the wettest locations. 
  Flash flooding is ongoing or expected to begin shortly.

  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.

* This Flash Flood Warning includes the entire island of Maui.

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 545 PM HST if flooding 
persists.

LAT...LON 2093 15672 2102 15668 2105 15660 2100 15652
      2091 15647 2096 15633 2095 15624 2087 15612
      2084 15611 2081 15599 2077 15597 2071 15598
      2064 15604 2061 15614 2057 15642 2063 15647
      2077 15648 2076 15654 2080 15663 2088 15670

FLASH FLOOD...RADAR INDICATED

$$

POWELL

1 follow-up statement

863 
WGHW70 PHFO 180145
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
345 PM HST Fri Dec 17 2021

HIC009-180155-
/O.CAN.PHFO.FF.W.0048.000000T0000Z-211218T0345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Maui HI-
345 PM HST Fri Dec 17 2021

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

The heavy rain across the west Maui mountains and leeward Haleakala 
slopes ended as abruptly as it began. Flooding is no longer expected 
to pose a threat.

LAT...LON 2093 15672 2102 15668 2105 15660 2100 15652
      2091 15647 2096 15633 2095 15624 2087 15612
      2084 15611 2081 15599 2077 15597 2071 15598
      2064 15604 2061 15614 2057 15642 2063 15647
      2077 15648 2076 15654 2080 15663 2088 15670

$$

POWELL

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 17, 2:10 PM HST	Areal Flood Advisory	HFO	Kalawao	35 min
Dec 17, 2:32 PM HST	Areal Flood Advisory	HFO	Honolulu	3 hr
Dec 17, 3:55 PM HST	Areal Flood Advisory	HFO	Honolulu	2 hr
Dec 17, 7:15 PM HST	Areal Flood Advisory	HFO	Hawaii	3 hr
Dec 18, 3:26 AM HST	Small Craft Advisory	HFO		6 days

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.