Alert archive / Louisiana / Tornado Watches in 2018
Tornado Watch 447
The Storm Prediction Center issued this tornado watch at Dec 27, 2018, 3:43 AM CST for 16 parishes in Louisiana; 16 counties in Texas. It was in force for 10 hr.
The area
The outline as issued.
The facts
- Issued
- Dec 27, 2018, 3:43 AM CST (09:43 UTC)
- Expired
- Dec 27, 2018, 1:18 PM CST
- In force
- 10 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 32 counties
Acadia Parish, LA, Allen Parish, LA, Beauregard Parish, LA, Calcasieu Parish, LA, Caldwell Parish, LA, Cameron Parish, LA, Evangeline Parish, LA, Grant Parish, LA, Jefferson Davis Parish, LA, LaSalle Parish, LA, Natchitoches Parish, LA, Rapides Parish, LA, Sabine Parish, LA, Vermilion Parish, LA, Vernon Parish, LA, Winn Parish, LA, Brazoria County, TX, Chambers County, TX, Fort Bend County, TX, Galveston County, TX, Hardin County, TX, Harris County, TX, Jackson County, TX, Jasper County, TX, Jefferson County, TX, Liberty County, TX, Matagorda County, TX, Newton County, TX, Orange County, TX, Sabine County, TX, Tyler County, TX, Wharton County, TX
The radar
The Houston radar (KHGX), 51 km from the middle of the area, began a volume at 09:45 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 SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 30%
- One or more EF2 to EF5 tornadoes
- 10%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 60%
Warnings issued inside it
20 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 27, 4:32 AM CST | Tornado Warning | HGX | Harris, Montgomery | 13 min |
| Dec 27, 4:39 AM CST | Severe Thunderstorm Warning | HGX | Harris | 9 min |
| Dec 27, 5:22 AM CST | Severe Thunderstorm Warning | SHV | Natchitoches, Sabine | 53 min |
| Dec 27, 6:38 AM CST | Tornado Warning | LCH | Rapides, Vernon | 37 min |
| Dec 27, 6:40 AM CST | Tornado Warning | SHV | Natchitoches, Sabine | 50 min |
| Dec 27, 7:11 AM CST | Tornado Warning | LCH | Vernon | 34 min |
| Dec 27, 7:11 AM CST | Tornado Warning | LCH | Calcasieu | 34 min |
| Dec 27, 7:37 AM CST | Tornado Warning | LCH | Calcasieu | 19 min |
| Dec 27, 8:30 AM CST | Severe Thunderstorm Warning | LCH | Allen, Calcasieu, Jefferson Davis | 30 min |
| Dec 27, 8:41 AM CST | Tornado Warning | LCH | Allen, Evangeline, Rapides | 34 min |
| Dec 27, 8:41 AM CST | Tornado Warning | LCH | Allen, Evangeline | 22 min |
| Dec 27, 9:14 AM CST | Tornado Warning | LCH | Avoyelles, Evangeline, Rapides | 31 min |
| Dec 27, 9:28 AM CST | Tornado Warning | LCH | Avoyelles, Evangeline, Saint Landry | 32 min |
| Dec 27, 9:42 AM CST | Tornado Warning | LCH | Acadia, Cameron, Jefferson Davis, Vermilion | 33 min |
| Dec 27, 9:55 AM CST | Flash Flood Warning | LCH | Acadia, Calcasieu, Evangeline, Jefferson Davis | 3 hr |
| Dec 27, 9:57 AM CST | Flash Flood Warning | LCH | Avoyelles, Rapides | 3 hr |
| Dec 27, 10:14 AM CST | Tornado Warning | LCH | Acadia, Lafayette, Vermilion | 31 min |
| Dec 27, 10:21 AM CST | Flash Flood Warning | LCH | Acadia | 2 hr |
| Dec 27, 11:22 AM CST | Flash Flood Warning | LCH | Lafayette, Vermilion | 3 hr |
| Dec 27, 12:07 PM CST | Flash Flood Warning | LCH | Vermilion | 113 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Lake Charles Mun, LA (KLCH), launched 00:00Z, 9.7 hours before the alert went out and 150 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 555 m above ground
- 0-6 km bulk shear
- 52 kt
- 0-1 km storm-relative helicity
- 339 m²/s²
- 0-3 km storm-relative helicity
- 586 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.7
The text
As transmitted.
806 WWUS20 KWNS 270939 SEL7 SPC WW 270939 LAZ000-TXZ000-CWZ000-271700- URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 447 NWS Storm Prediction Center Norman OK 340 AM CST Thu Dec 27 2018 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Central and southwest Louisiana Southeast Texas Coastal Waters * Effective this Thursday morning from 340 AM until 1100 AM CST. * Primary threats include... A couple tornadoes possible Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...A line of thunderstorms will move across the watch area this morning posing a risk for isolated damaging winds and a couple of tornadoes. The tornado watch area is approximately along and 60 statute miles north and south of a line from 10 miles north of Palacios TX to 50 miles east southeast of Fort Polk LA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && OTHER WATCH INFORMATION...CONTINUE...WW 445...WW 446... AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean storm motion vector 24040. ...Bunting
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 26, 11:40 PM CST | Mesoscale Discussion | SPC | Bossier, Caddo, De Soto | 2 hr |
| Dec 27, 12:02 AM CST | Severe Thunderstorm Watch | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Red River and 1 more | 5 hr |
| Dec 27, 1:39 AM CST | Mesoscale Discussion | SPC | Bienville, Bossier, Caddo, Claiborne, De Soto, Lincoln and 2 more | 2 hr |
| Dec 27, 3:09 AM CST | Mesoscale Discussion | SPC | Allen, Beauregard, Calcasieu, Cameron, Jefferson Davis, Vernon | 2 hr |
| Dec 27, 7:12 AM CST | Mesoscale Discussion | SPC | Acadia, Allen, Avoyelles, Beauregard, Calcasieu, Cameron and 11 more | 2 hr |
| Dec 27, 9:00 AM CST | Mesoscale Discussion | SPC | Avoyelles, Catahoula, Concordia, East Baton Rouge, East Feliciana, Iberville and 6 more | 60 min |
| Dec 27, 9:29 AM CST | Tornado Watch | SPC | Ascension, Assumption, Avoyelles, Catahoula, Concordia, East Baton Rouge and 27 more | 9 hr |
| Dec 27, 1:50 PM CST | Mesoscale Discussion | SPC | Ascension, Assumption, Catahoula, Concordia, East Baton Rouge, East Feliciana and 19 more | 85 min |
| Dec 26, 7:13 PM CST | Mesoscale Discussion | SPC | Bell, Bosque, Collin, Cooke, Dallas, Delta and 22 more | 2 hr |
| Dec 26, 8:51 PM CST | Mesoscale Discussion | SPC | Atascosa, Bandera, Bastrop, Bexar, Blanco, Caldwell and 18 more | 114 min |
| Dec 26, 9:34 PM CST | Tornado Watch | SPC | Anderson, Angelina, Brazos, Burleson, Cherokee, Falls and 29 more | 6 hr |
Nearby
Tornado Watches in Louisiana, 2018Tornado Watches in Texas, 2018Every tornado watch in 2018
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.