Alert archive / Hawaii / Flash Flood Warnings in 2020

Flash Flood Warning 1, NWS Honolulu, HI

January 11, 2020Hawaii County, Hawaii

NWS Honolulu, HI issued this flash flood warning at Jan 11, 2020, 7:35 PM HST for Hawaii County, Hawaii. It was in force for 21 hr. 4 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jan 11, 2020, 7:35 PM HST (05:35 UTC)
Expired: Jan 12, 2020, 4:30 PM HST
In force: 21 hr
Issued by: NWS Honolulu, HI
Area: Storm-based polygon
Flood severity: None

County Hawaii County, HI

The radar

The South Shore radar (PHWA), 62 km from the middle of the area, began a volume at 05:34 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.

What was reported inside it

Time	Report	Where	Remark
Jan 11, 9:04 PM HST	FLASH FLOOD	Hilo, HI	HWY CLOSURE - SADDLE RD NEAR MILE MARKER 11
Jan 11, 9:04 PM HST	FLASH FLOOD	Pahala, HI	HIGHWAY 11 CLOSED NEAR KAWA FLATS
Jan 12, 2:03 AM HST	FLASH FLOOD	Hilo, HI	BAYFRONT HIGHWAY, PAUAHI ST, AND KAMEHAMEHA AVE CLOSED DUE TO HEAVY PONDING AND RUNOFF.
Jan 12, 4:05 AM HST	FLASH FLOOD	3 E Mountain View, HI	AN OCCUPIED VEHICLE WAS REPORTED TO HAVE GONE INTO FLOODED AREA OF KAHIKOPELE ST AND SOUTH KOPUA ROAD IN EDEN ROCK. VEHICLE BECAME FILLED WITH WATER.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched 5 storm reports to this flash flood warning; the first came 89 minutes after it went out.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Hilo, (PITO), launched 00:00Z, 5.6 hours before the alert went out and 41 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: 620 J/kg
Mixed-layer CIN: -11 J/kg
Mixed-layer LCL: 786 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 4 m²/s²
0-3 km storm-relative helicity: 45 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

330 
WGHW50 PHFO 120535
FFWHFO
HIC001-120830-
/O.NEW.PHFO.FF.W.0001.200112T0535Z-200112T0830Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
735 PM HST Sat Jan 11 2020

The National Weather Service in Honolulu has issued a

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

* Until 1030 PM HST.

* At 728 PM HST, radar indicated heavy rainfall over the windward 
  slopes of the Big Island. The most intense area of rainfall was 
  over the slopes above Hilo with rates of more than 2 inches per 
  hour. This rainfall will cause the water level in an already 
  swollen Wailuku River to rise further. Heavy rain along the 
  Hamakua Coast will also cause flooding problems along Belt Highway 
  between Honomu and Honokaa.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and rain gages.

  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 flooding include...
  Hilo, Naalehu, Waipio Valley, Orchidland Estates, Hawi, Pepeekeo, 
  Keaau, Hawaiian Paradise Park, Kawa Flats, Pahoa, Kapaau and 
  Hawaiian Acres.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

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

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. 

&&

This warning may need to be extended beyond 1030 PM HST if heavy rain
persists.

This Flash Flood Warning replaces the previously issued Flood
Advisory that was in effect for portions of the island of Hawaii in
Hawaii County.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...RADAR AND GAGE INDICATED

$$

Kodama

9 follow-up statements

048 
WGHW50 PHFO 120820
FFWHFO
HIC001-121130-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200112T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
1020 PM HST Sat Jan 11 2020

The National Weather Service in Honolulu has extended the

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

* Until 130 AM HST.

* At 1016 PM HST, radar and rain gages indicated heavy rainfall over 
  the windward and southeast facing slopes of the Big Island. The 
  most intense area of rainfall was over the slopes from Hilo to 
  South Point with rates of more than 2 inches per hour. This 
  rainfall will cause the water levels in already swollen streams to 
  rise further. Heavy rain along the Hamakua Coast will also cause 
  flooding problems along Belt Highway between Honomu and Honokaa.
  

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and rain gages.

  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 flooding include...
  Hilo, Naalehu, Waipio Valley, Orchidlands Estates, Hawi, Pepeekeo,
  Keaau, Hawaiian Paradise Park, Kawa Flats, Pahoa, Kapaau and
  Hawaiian Acres.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

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

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. 

&&

This warning may need to be extended beyond 130 AM HST if heavy rain
persists.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...RADAR AND GAGE INDICATED

$$

Powell

755 
WGHW50 PHFO 121112
FFWHFO
HIC001-121430-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200112T1430Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
112 AM HST Sun Jan 12 2020

The National Weather Service in Honolulu has extended the

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

* Until 430 AM HST.

* At 107 AM HST, radar and rain gages indicated heavy rainfall 
  continues over windward and southeast facing slopes of the Big 
  Island. The most intense area of rainfall was over the slopes from 
  Hilo to South Point with rates of more than 2 inches per hour, 
  closing Highway 11 at Kawa Flats. This rainfall will cause water 
  levels in already swollen streams to rise further. Heavy rain 
  along the Hamakua Coast will also continue to cause flooding 
  problems along the Belt Highway between Honomu and Honokaa.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and rain gages.

  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 flooding include...
  Hilo, Naalehu, Waipio Valley, Orchidlands Estates, Hawi, Pepeekeo,
  Keaau, Hawaiian Paradise Park, Kawa Flats, Pahoa, Kapaau and
  Hawaiian Acres.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

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

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. 

&&

This warning may need to be extended beyond 430 AM HST if heavy rain
persists.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...RADAR AND GAGE INDICATED

$$

Powell

180 
WGHW50 PHFO 121418
FFWHFO
HIC001-121730-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200112T1730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
418 AM HST Sun Jan 12 2020

The National Weather Service in Honolulu has extended the

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

* Until 730 AM HST.

* At 409 AM HST, radar and rain gages indicated moderate to heavy 
  rainfall continues across a broad swath of windward and southeast 
  slopes of the Big Island. While rainfall rates have decreased 
  somewhat, into the 1 to 2 inch per hour range, the Wailuku River 
  remains dangerously high and reports of road closures continue. 

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and rain gages.

  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 flooding include...
  Hilo, Naalehu, Waipio Valley, Orchidlands Estates, Hawi, Pepeekeo,
  Keaau, Hawaiian Paradise Park, Kawa Flats, Pahoa, Kapaau and
  Hawaiian Acres.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

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

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. 

&&

This warning may need to be extended beyond 730 AM HST if heavy rain
persists.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...RADAR AND GAGE INDICATED

$$

Powell

433 
WGHW70 PHFO 121646
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
646 AM HST Sun Jan 12 2020

HIC001-121730-
/O.CON.PHFO.FF.W.0001.000000T0000Z-200112T1730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hawaii in Hawaii HI-
646 AM HST Sun Jan 12 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 730 AM HST FOR
HAWAII IN HAWAII COUNTY...

At 630 AM HST, Big Island Civil Defense reported numerous road 
closures across the Big Island, due to heavy runoff and debris on 
roadways. Portions of Saddle road are closed, Highway 11 is closed 
near Kawa Flats, and Highway 19 is closed north of Honokaa due to a 
large tree blocking the road. Additional rainfall on already 
saturated ground is leading to extreme runoff and ponding. Avoid 
unnecessary travel.  

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.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

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

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. 

&&

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...OBSERVED

$$

Birchard

261 
WGHW50 PHFO 121728
FFWHFO
HIC001-122030-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200112T2030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
728 AM HST Sun Jan 12 2020

The National Weather Service in Honolulu has extended the

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

* Until 1030 AM HST.

* At 725 AM HST, radar showed moderate rain occurring over most of 
  the Big Island, with some embedded heavy showers, and flooding 
  impacts continue, primarily on the windward side. Big Island Civil 
  Defense reports numerous road closures, due to heavy runoff and 
  debris on roadways. Portions of Saddle road are closed, Highway 11 
  is closed near Kawa Flats, and Highway 19 is closed north of 
  Honokaa due to a large tree blocking the road. 

  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 flooding include...
  Windward Big Island from Upolu Point to Honokaa to Hilo to South 
  Point. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Warning means that flooding is imminent or occurring
within the warned area.

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

Do not cross fast flowing 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 1030 AM HST if heavy rain
persists.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...OBSERVED

$$

Birchard

541 
WGHW70 PHFO 121853
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
853 AM HST Sun Jan 12 2020

HIC001-122030-
/O.CON.PHFO.FF.W.0001.000000T0000Z-200112T2030Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hawaii in Hawaii HI-
853 AM HST Sun Jan 12 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 1030 AM HST FOR
HAWAII IN HAWAII COUNTY...

At 850 AM HST, Big Island Civil Defense reported that significant 
flooding continues to impact most of windward Big Island. Many 
roadways are closed, and unnecessary travel should be avoided. Over 
20 inches of rain has fallen over some windward areas in the last 24 
hours, and extreme runoff and flooding impacts continue. Highway 11 
is closed near Kawa Flats, Saddle Road is closed, and a large tree 
is blocking Highway 19 near Honokaa. 

HAZARD...Life threatening flash flooding.

SOURCE...Emergency management.

IMPACT...Significant and life threatening flooding in drainages, 
         streams, rivers, roads, properties, and other low lying 
         areas. Multiple public road closures occurring, as well as 
         landslides in steep terrain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

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

&&

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Birchard

689 
WGHW50 PHFO 122026
FFWHFO
HIC001-122330-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200112T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
1026 AM HST Sun Jan 12 2020

The National Weather Service in Honolulu has extended the

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

* Until 130 PM HST.

* At 1022 AM HST, radar showed moderate rain occurring over most of 
  the Big Island, with some embedded heavy showers, however 
  significant flooding impacts continue, primarily on the windward 
  side. Big Island Civil Defense reports numerous road closures, due 
  to heavy runoff and debris on roadways. Avoid unnecessary travel. 

  HAZARD...Life threatening flash flooding.

  SOURCE...Emergency management.

  IMPACT...Significant and life threatening flooding in drainages, 
           streams, rivers, roads, properties, and other low lying 
           areas. Multiple public road closures expected, as well as 
           landslides in steep terrain.

* Some locations that will experience flooding include...
  Windward Big Island from Upolu Point to Honokaa to Hilo to South 
  Point. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

This warning may need to be extended beyond 130 PM HST if heavy rain
persists.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Birchard

511 
WGHW50 PHFO 122324
FFWHFO
HIC001-130230-
/O.EXT.PHFO.FF.W.0001.000000T0000Z-200113T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Honolulu HI
124 PM HST Sun Jan 12 2020

The National Weather Service in Honolulu has extended the

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

* Until 430 PM HST.

* At 120 PM HST, emergency management reported that significant 
  flooding impacts continued across windward Big Island, with 
  numerous road closures reported. In addition, radar showed newly-
  developed heavy showers affecting the area from Hilo to Volcano to 
  Pahala that were spreading upslope, and toward the Hamakua 
  District. 

  HAZARD...Life threatening flash flooding.

  SOURCE...Emergency management.

  IMPACT...Significant and life threatening flooding in drainages, 
           streams, rivers, roads, properties, and other low lying 
           areas. Multiple public road closures expected, as well as 
           landslides in steep terrain.

* Some locations that will experience flooding include...
  Windward Kohala, Hamakua, Hilo, Puna and Kau Districts.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

This warning may need to be extended beyond 430 PM HST if flooding 
continues.

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...OBSERVED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Birchard

123 
WGHW70 PHFO 130111
FFSHFO

Flash Flood Statement
National Weather Service Honolulu HI
311 PM HST Sun Jan 12 2020

HIC001-130230-
/O.CON.PHFO.FF.W.0001.000000T0000Z-200113T0230Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hawaii in Hawaii HI-
311 PM HST Sun Jan 12 2020

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 430 PM HST FOR
HAWAII IN HAWAII COUNTY...

At 310 PM HST, radar indicated moderate to heavy showers falling 
over windward Big Island slopes from Volcano to Hilo to Hawi, where 
the ground is saturated from recent rainfall. Flooding and severe 
ponding persists in many areas of windward Big Island, and Highway 
11 near Kawa Flats in the Kau District remains closed due to water 
on the roadway. Unnecessary travel should be postponed. 

HAZARD...Heavy rain producing life threatening flash flooding.

SOURCE...Radar indicated.

IMPACT...Significant and life threatening flooding in drainages, 
         streams, rivers, roads, properties, and other low lying 
         areas. Multiple public road closures expected, as well as 
         landslides in steep terrain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

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

&&

LAT...LON 1934 15499 1927 15516 1927 15529 1913 15551
      1892 15566 1892 15568 1899 15576 1954 15532
      1983 15540 2020 15591 2025 15590 2027 15587
      2025 15577 2012 15559 2001 15526 1985 15509
      1974 15510 1974 15500 1965 15499 1953 15481

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

Birchard

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Honolulu, HI wrote its last area forecast discussion before this flash flood warning went out at Jan 11, 4:05 PM HST, 3 hours 30 minutes earlier.

Area forecast discussion, Jan 11, 4:05 PM HST, 3 hours 30 minutes before

Area Forecast Discussion
National Weather Service Honolulu HI
405 PM HST Sat Jan 11 2020

.SYNOPSIS...
Wet and windy weather will continue for another couple of days, as
an upper level disturbance lingers west of the islands. Strong
easterly trade winds will continue through the weekend, then shift
to the east-southeast early next week as a surface low develops
northwest of Kauai. The potential for localized flash flooding will
continue through the weekend, especially over windward and mountain
areas, where soils remain saturated. Some drying is possible around
Tuesday and Wednesday, but another disturbance may bring a return of
wet weather, but lighter winds, Thursday into Friday. A drier trade
wind flow may develop by next weekend.

&&

.DISCUSSION...
The combination of strong high pressure centered to the NNE of the
islands and a developing low NW of Kauai will keep strong E trade
winds over the islands through the weekend. As the low tracks N
early next week, winds will remain elevated as they veer to the ESE.
A convergence band associated with the low is expected to keep wet
weather in place over the islands until Tuesday/Wednesday, when the
convergence band may shift just W of the islands, bringing the
potential for a brief drying trend. Latest guidance brings an upper
trough and associated front (with lighter winds) over the islands
around Thursday, with the potential for a drier, cooler breezy NE
flow to develop by next weekend.

In the meantime, a closed low aloft centered just W of the islands
is supporting an unstable island atmosphere, while the strong trade
winds continue to stream an abundant amount of low-level moisture
over the islands from the E. A Flash Flood Watch remains in effect
for all islands as localized heavy downpours could quickly lead to
flash flooding given how saturated the ground is, especially in
windward areas. In some areas, like windward Big Island today,
showers are not necessarily advecting in from the ocean. Instead,
the terrain-anchored heavy rainfall appears to be developing in
response to orographic lift supplied by the strong trades
interacting with the dynamic large-scale lift provided by the low
aloft. This persistent rain is resulting in dangerously high water
levels in windward Big Island's Honolii Stream and Wailuku River.
Water levels in Oahu's Lake Wilson are also very high, although a
break in rainfall on Oahu has slowed the rate of water rise today.

The best chance for flash flooding through the weekend will remain
over windward and mountain areas, where soils are saturated and
streams are running high from the incessantly steady rainfall over
the past few days, but streams statewide (even those in leeward
areas) can be expected to be running higher than normal. Moisture is
sufficiently deep to impact the summits of Maui and the Big Island,
and a Winter Storm Warning is now in effect for Mauna Kea and Mauna
Loa, where near- to below-freezing temperatures, accumulating snow
showers and low visibility are occurring.

As the surface low develops NW of Kauai, and the low-level flow is
expected to veer to the ESE. While this flow normally places the
smaller islands in the wind shadow of the Big Island, it remains
uncertain how much veering will occur, and thus how much reduction
in wind speed is realized over land. Guidance indicates a surge in
east to east-southeast wind speeds Sunday night and Monday, which
may require another Wind Advisory for portions of the state.

The low aloft is expected to lifts slowly N over the next couple of
days, while a surface low develops in response. While mid-level
temperatures gradually warm over the islands early next week as this
occurs (leading to a reduction in the instability), a low-level
convergence band over the area is expected to keep wet weather in
place through Monday, especially over the W end of the state. The
convergence band may slide sufficiently W of the area to allow a
brief drying trend Tuesday/Wednesday, but confidence in those
details are low. An upper trough and surface front bring the
potential for wet weather by Thursday, but latest guidance shows a
cool, breezy and drier NE trade wind flow developing by next
weekend as the deep moisture moves E of the islands.

&&

.AVIATION...
Strong high pressure system north of the state will continue breezy
to windy trade winds. A west to east oriented trough aloft and
subtropical jet will continue to produce wet and unsettled weather
across the region with heavy rain and the chance for thunderstorms
expected through the next 24 hours. Periods of MVFR and IFR
conditions will occur due to low ceilings/visibility in developing
shower bands, especially along north through east facing sections of
each island.

AIRMET Sierra for Tempo Mountain Obscuration will continue for north
through east sections of Kauai, Oahu, Molokai, Maui, and the Big
Island. These conditions will likely remain for the next 24 hours.

AIRMET Tango remains in effect for Tempo Moderate Turbulence over
and immediately south through west of all island terrain. Another
AIRMET Tango was issued for Tempo Moderate Turbulence aloft between
FL200 and FL350 due to strong jet stream winds. A third AIRMET Tango
remains in effect for strong surface winds greater than 30 KT for
the area around Kauai, but will be dropped for all other areas. The
surface wind AIRMET may need to be reissued tomorrow as winds come
back up.

&&

.MARINE...
Strong high pressure far north of the state will maintain strong to
near gale force trade winds through the middle of next week with a
slight uptick in wind speeds possible Sunday night into Monday.
Small Craft Advisories (SCA) are in effect for all Hawaiian waters
due to a combination of strong winds and large seas. A Gale Watch is
also in effect for the Alenuihaha Channel Sunday night through
Monday. Winds should begin to decrease during the second half of
next week as a front passes north of the state, causing the high to
weaken and shift further east.

An unstable airmass over the islands will continue to bring the
chance for locally heavy downpours and a risk for thunderstorms
through at least Sunday afternoon and possibly into Monday.

The High Surf Warning for east facing shores of Kauai, Oahu,
Molokai, Maui and the Big Island has been downgraded to a High Surf
Advisory. Although surf heights have dropped a little over the last
day, we should continue to see elevated surf through the middle of
next week. As the winds begin to decrease during the second half of
the week, surf should drop below advisory levels by Friday.

The current long-period northwest swell will continue to gradually
decrease over the next few days, with a smaller reinforcing
northwest swell filling in on Sunday. These swells should drop to
background levels by Tuesday with minimal swells expected through
most of next week. A front passing north of the state late next week
may produce a moderate short-period north swell towards the end of
next week. Otherwise, no significant swells are expected through
next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Sunday afternoon for all islands.

High Surf Advisory until 6 AM HST Thursday for East facing shores of
Kauai Oahu Molokai Maui and the Big Island.

Winter Storm Warning until 6 PM HST Sunday for Big Island Summits.

Small Craft Advisory until 6 PM HST Monday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu
Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County
Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo
Channel-Big Island Windward Waters-Big Island Leeward Waters-Big
Island Southeast Waters.

Gale Watch from Sunday evening through Monday afternoon for
Alenuihaha Channel.

Small Craft Advisory until 6 PM HST Sunday for Alenuihaha Channel.

&&

DISCUSSION...Birchard
AVIATION...TS
MARINE...Kino

The office that day

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

Issued	Product	Office	Counties	Lasted
Jan 11, 2:52 PM HST	Winter Storm Warning	HFO	Hawaii	37 hr
Jan 11, 3:29 PM HST	High Surf Advisory	HFO	Honolulu, Kalawao	5 days
Jan 11, 6:30 PM HST	Areal Flood Advisory	HFO	Honolulu	3 hr
Jan 12, 1:04 AM HST	Areal Flood Advisory	HFO	Kalawao	3 hr
Jan 12, 3:18 AM HST	Gale Warning	HFO		54 hr
Jan 12, 3:45 AM HST	Flash Flood Warning	HFO	Kalawao	5 hr

Nearby

Flash Flood Warnings in Hawaii, 2020 Every flash flood warning in 2020

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.