Alert archive / Louisiana / Mesoscale Discussions in 2014

Mesoscale Discussion 1913

November 16, 2014Washington County, Alabama; 18 parishes in Louisiana; 13 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Nov 16, 2014, 8:43 PM CST for Washington County, Alabama; 18 parishes in Louisiana; 13 counties in Mississippi. It was in force for 62 min.

The area

The outline as issued.

The facts

Issued: Nov 16, 2014, 8:43 PM CST (02:43 UTC)
Expired: Nov 16, 2014, 9:45 PM CST
In force: 62 min
Issued by: the Storm Prediction Center

All 32 counties

Washington County, AL, Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, St. Mary Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, Forrest County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jones County, MS, Lamar County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Stone County, MS, Walthall County, MS, Wayne County, MS

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 551Nov 16, 9:50 PM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 2.7 hours before the alert went out and 29 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: 496 J/kg
Mixed-layer CIN: -36 J/kg
Mixed-layer LCL: 825 m above ground
0-6 km bulk shear: 44 kt
0-1 km storm-relative helicity: 295 m²/s²
0-3 km storm-relative helicity: 414 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 5.3

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

249 
ACUS11 KWNS 170243
SWOMCD
SPC MCD 170243 
ALZ000-MSZ000-LAZ000-170345-

MESOSCALE DISCUSSION 1913
NWS STORM PREDICTION CENTER NORMAN OK
0843 PM CST SUN NOV 16 2014

AREAS AFFECTED...SERN LA / SRN MS / FAR SWRN AL

CONCERNING...TORNADO WATCH 550...

VALID 170243Z - 170345Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 550 CONTINUES.

SUMMARY...THE POSSIBILITY FOR TORNADOES WILL LIKELY PERSIST BEYOND
THE 04Z EXPIRATION TIME OF TORNADO WATCH 550.  A REPLACEMENT TORNADO
WATCH WILL LIKELY BE NEEDED WITHIN AN HOUR OR SO AND WILL COVER ERN
PORTIONS OF WATCH 550 AND INCLUDE DOWNSTREAM AREAS OVER SRN MS...FAR
SERN LA...AND PERHAPS FAR SWRN AL.

DISCUSSION...THE 00Z LIX RAOB SAMPLED AN ADEQUATELY MOIST/MARGINALLY
UNSTABLE AIRMASS OVER THE LOWER MS RIVER VALLEY TO THE S OF A MARINE
WARM FRONT LOCATED OVER SRN MS AND SRN AL.  STRONG LOW-LEVEL WIND
SHEAR /270 M2 PER S2 EFFECTIVE SRH PER OBSERVED STORM MOTIONS/ AND
LOOPING HODOGRAPHS WILL SUPPORT LOW-LEVEL MESOCYCLOGENESIS AND THE
POSSIBILITY FOR A FEW TORNADOES PERSISTING FOR AT LEAST THE NEXT FEW
HOURS.

SHORT-TERM...THE AREAS DOWNSTREAM OF THE LIVINGSTON/ST. HELENA
PARISH LA TORNADIC SUPERCELL WILL LIKELY EXHIBIT THE GREATEST
NEAR-TERM TORNADO POTENTIAL COMPARED TO OTHER AREAS OF THE REGION.  

LONGER-TERM...STRENGTHENING FLOW FIELDS AND INCREASING ASCENT
ASSOCIATED WITH THE APPROACHING SHORTWAVE TROUGH WILL SUPPORT THE
POTENTIAL FOR ORGANIZED STORM STRUCTURES /SUPERCELLS AND BOWING
LEWPS/ LATE TONIGHT.  THE LONGER-LIVED CIRCULATIONS WILL PROBABLY BE
MOST ASSOCIATED WITH THE THREAT FOR ISOLD DAMAGING WINDS AND A
TORNADO OR TWO.

..SMITH/MEAD.. 11/17/2014

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MOB...JAN...LIX...LCH...

LAT...LON   29159033 29259127 29619191 30359143 31828923 31958837
            31578802 31048829 29159033

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 16, 9:49 PM CST	Tornado Watch	SPC	Mobile, Washington	7 hr
Nov 16, 11:50 PM CST	Mesoscale Discussion	SPC	Choctaw, Clarke, Escambia, Monroe, Washington	55 min
Nov 17, 1:13 AM CST	Mesoscale Discussion	SPC	Baldwin, Barbour, Butler, Coffee, Conecuh, Covington and 8 more	32 min
Nov 17, 1:32 AM CST	Tornado Watch	SPC	Baldwin, Barbour, Bullock, Butler, Clarke, Coffee and 11 more	7 hr
Nov 17, 2:21 AM CST	Mesoscale Discussion	SPC	Mobile, Washington	114 min
Nov 17, 4:39 AM CST	Mesoscale Discussion	SPC	Baldwin, Barbour, Bullock, Butler, Coffee, Conecuh and 9 more	66 min
Nov 17, 7:43 AM CST	Mesoscale Discussion	SPC	Barbour, Dale, Geneva, Henry, Houston	92 min

Nearby

Mesoscale Discussions in Louisiana, 2014 Mesoscale Discussions in Mississippi, 2014 Mesoscale Discussions in Alabama, 2014 Every mesoscale discussion in 2014

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.