Alert archive / Texas / Flash Flood Warnings in 2021

Flash Flood Warning 39, NWS Houston/Galveston, TX

October 1, 2021Polk County, San Jacinto County, Trinity County, Texas

NWS Houston/Galveston, TX issued this flash flood warning at Oct 1, 2021, 8:38 AM CDT for Polk County, San Jacinto County, Trinity County, Texas. It was in force for 3 hr. 1 report 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: Oct 1, 2021, 8:38 AM CDT (13:38 UTC)
Expired: Oct 1, 2021, 11:54 AM CDT
In force: 3 hr
Issued by: NWS Houston/Galveston, TX
Area: Storm-based polygon
Flood severity: None

Counties Polk County, TX, San Jacinto County, TX, Trinity County, TX

The radar

The Houston radar (KHGX), 155 km from the middle of the area, began a volume at 13:40 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
Oct 1, 8:45 AM CDT	FLASH FLOOD	4 Wsw Onalaska, TX	REPORTS OF ROADS BECOMING IMPASSABLE IN THE HOLIDAY VILLAGE AREA OFF OF US HIGHWAY 190.

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

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 1.6 hours before the alert went out and 209 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: 1808 J/kg
Mixed-layer CIN: -10 J/kg
Mixed-layer LCL: 585 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: 30 m²/s²
0-3 km storm-relative helicity: 57 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.2

Open this sounding in Storm Lab

The text

As transmitted.

648 
WGUS54 KHGX 011338
FFWHGX
TXC373-407-455-011700-
/O.NEW.KHGX.FF.W.0039.211001T1338Z-211001T1700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Houston/Galveston TX
838 AM CDT Fri Oct 1 2021

The National Weather Service in League City has issued a

* Flash Flood Warning for...
  West Central Polk County in southeastern Texas...
  Northwestern San Jacinto County in southeastern Texas...
  South Central Trinity County in southeastern Texas...

* Until noon CDT.

* At 838 AM CDT, Doppler radar and automated rain gauges indicated 
  thunderstorms producing heavy rain across the warned area. Between 
  2 and 5 inches of rain have fallen, much of that in the past hour. 
  The expected rainfall rate is 1.5 to 3.75 inches in 1 hour. Flash 
  flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar and automated gauges.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Onalaska and Sebastopol.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

Flooding is occurring or is imminent. It is important to know where 
you are relative to streams, rivers, or creeks which can become 
killers in heavy rains. Campers and hikers around Lake Livingston 
should return to safe shelter.

&&

LAT...LON 3090 9531 3092 9530 3093 9526 3091 9517
      3090 9514 3086 9510 3083 9509 3081 9509
      3079 9512 3079 9517 3079 9522 3082 9528
      3083 9530 3087 9532

FLASH FLOOD...RADAR AND GAUGE INDICATED
EXPECTED RAINFALL...1.5-3.75 INCHES IN 1 HOUR

$$

1 follow-up statement

223 
WGUS74 KHGX 011654
FFSHGX

Flash Flood Statement
National Weather Service Houston/Galveston TX
1154 AM CDT Fri Oct 1 2021

TXC373-407-455-011704-
/O.CAN.KHGX.FF.W.0039.000000T0000Z-211001T1700Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Polk TX-San Jacinto TX-Trinity TX-
1154 AM CDT Fri Oct 1 2021

...FLASH FLOOD WARNING FOR WEST CENTRAL POLK, NORTHWESTERN SAN 
JACINTO AND SOUTH CENTRAL TRINITY COUNTIES HAS BEEN REPLACED WITH A 
FLOOD ADVISORY...

LAT...LON 3090 9531 3092 9530 3093 9526 3091 9517
      3090 9514 3086 9510 3083 9509 3081 9509
      3079 9512 3079 9517 3079 9522 3082 9528
      3083 9530 3087 9532

$$

The office that day

Everything else NWS Houston/Galveston, TX issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 1, 5:37 AM CDT	Areal Flood Advisory	HGX	Chambers, Harris, Liberty	27 min
Oct 1, 5:57 AM CDT	Areal Flood Advisory	HGX	Austin, Grimes, Waller, Washington	2 hr
Oct 1, 6:04 AM CDT	Flash Flood Warning	HGX	Harris	3 hr
Oct 1, 6:52 AM CDT	Areal Flood Advisory	HGX	Harris	113 min
Oct 1, 7:23 AM CDT	Areal Flood Advisory	HGX	Fort Bend, Harris, Waller	67 min
Oct 1, 7:40 AM CDT	Areal Flood Advisory	HGX	Austin, Grimes, Harris, Waller, Washington	99 min
Oct 1, 8:29 AM CDT	Flash Flood Warning	HGX	Fort Bend, Harris, Waller	3 hr
Oct 1, 8:34 AM CDT	Areal Flood Advisory	HGX	Harris, Montgomery	65 min
Oct 1, 9:01 AM CDT	Areal Flood Warning	HGX	Chambers, Harris, Liberty	5 hr
Oct 1, 9:19 AM CDT	Flash Flood Warning	HGX	Grimes, Waller, Washington	3 hr
Oct 1, 9:25 AM CDT	Areal Flood Advisory	HGX	Fort Bend	3 hr
Oct 1, 9:37 AM CDT	Areal Flood Advisory	HGX	Harris	3 hr
Oct 1, 10:57 AM CDT	Areal Flood Warning	HGX	Fort Bend, Harris, Waller	3 hr
Oct 1, 11:01 AM CDT	Areal Flood Advisory	HGX	Liberty, San Jacinto	3 hr
Oct 1, 11:08 AM CDT	River Flood Warning	HGX	Harris	4 hr
Oct 1, 11:54 AM CDT	Areal Flood Advisory	HGX	Polk, San Jacinto, Trinity	2 hr
Oct 1, 12:02 PM CDT	Areal Flood Warning	HGX	Austin, Grimes, Harris, Waller, Washington	2 hr
Oct 1, 12:42 PM CDT	Areal Flood Advisory	HGX	Fort Bend, Harris, Montgomery	78 min

Nearby

Flash Flood Warnings in Texas, 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.