Alert archive / Texas / Flash Flood Warnings in 2021

Flash Flood Warning 34, NWS Houston/Galveston, TX

September 14, 20214 counties in Texas

NWS Houston/Galveston, TX issued this flash flood warning at Sep 14, 2021, 1:43 AM CDT for 4 counties in Texas. It was in force for 4 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: Sep 14, 2021, 1:43 AM CDT (06:43 UTC)
Expired: Sep 14, 2021, 5:45 AM CDT
In force: 4 hr
Issued by: NWS Houston/Galveston, TX
Area: Storm-based polygon
Flood severity: None

Counties Brazoria County, TX, Galveston County, TX, Harris County, TX, Matagorda County, TX

The radar

The Houston radar (KHGX), 24 km from the middle of the area, began a volume at 06:43 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

Lake Charles Mun, LA (KLCH), launched 00:00Z, 6.7 hours before the alert went out and 208 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: 528 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 794 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 53 m²/s²
0-3 km storm-relative helicity: 327 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 2.3

Open this sounding in Storm Lab

The text

As transmitted.

085 
WGUS54 KHGX 140643
FFWHGX
TXC039-167-201-321-141045-
/O.NEW.KHGX.FF.W.0034.210914T0643Z-210914T1045Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Houston/Galveston TX
143 AM CDT Tue Sep 14 2021

The National Weather Service in League City has issued a

* Flash Flood Warning for...
  Central Brazoria County in southeastern Texas...
  Galveston County in southeastern Texas...
  Harris County in southeastern Texas...
  East Central Matagorda County in southeastern Texas...

* Until 545 AM CDT.

* At 143 AM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Flash flooding is ongoing or 
  expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  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...
  Southern Pasadena, League City, Galveston Island West End, 
  Galveston Causeway, Texas City, southern Friendswood, Lake 
  Jackson, Alvin, Angleton, Dickinson, La Marque, Santa Fe, 
  Freeport, Clute, Webster, Hitchcock, Kemah, Surfside Beach, 
  southeastern Clear Lake and Galveston Pier 21.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 2880 9583 2903 9567 2940 9533 2958 9511
      2952 9498 2951 9486 2947 9487 2941 9481
      2951 9471 2950 9456 2948 9454 2936 9472
      2933 9471 2882 9545 2862 9589

FLASH FLOOD...RADAR INDICATED

$$

kp

The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 13, 7:32 PM CDT	Flash Flood Warning	HGX	Brazoria, Jackson, Matagorda	3 hr
Sep 13, 9:46 PM CDT	Flash Flood Warning	HGX	Brazoria, Galveston, Matagorda	4 hr
Sep 13, 10:06 PM CDT	Hurricane Warning	HGX	Brazoria, Jackson, Matagorda	6 hr
Sep 13, 10:31 PM CDT	Flash Flood Warning	HGX	Matagorda	3 hr
Sep 14, 3:33 AM CDT	Flash Flood Warning	HGX	Brazoria, Chambers, Galveston, Harris	4 hr
Sep 14, 3:57 AM CDT	Small Craft Advisory	HGX		18 hr
Sep 14, 4:04 AM CDT	Coastal Flood Advisory	HGX	Brazoria, Chambers, Galveston, Harris, Matagorda	14 hr
Sep 14, 4:42 AM CDT	River Flood Warning	HGX	Galveston, Harris	28 hr
Sep 14, 5:29 AM CDT	River Flood Warning	HGX	Galveston, Harris	21 days
Sep 14, 5:31 AM CDT	River Flood Warning	HGX	Galveston, Harris	21 days
Sep 14, 5:45 AM CDT	Flash Flood Warning	HGX	Brazoria, Chambers, Galveston, Harris	3 hr
Sep 14, 8:11 AM CDT	Areal Flood Warning	HGX	Brazoria, Galveston, Harris	3 hr

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.