Alert archive / Louisiana / Mesoscale Discussions in 2017

Mesoscale Discussion 97

January 21, 2017Mobile County, Alabama; 28 parishes in Louisiana; 26 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Jan 21, 2017, 6:05 PM CST for Mobile County, Alabama; 28 parishes in Louisiana; 26 counties in Mississippi. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued
Jan 21, 2017, 6:05 PM CST (00:05 UTC)
Expired
Jan 21, 2017, 7:30 PM CST
In force
85 min
Issued by
the Storm Prediction Center
All 55 counties

Mobile County, AL, Ascension Parish, LA, Assumption Parish, LA, Avoyelles Parish, LA, Catahoula Parish, LA, Concordia Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Franklin Parish, LA, Iberville Parish, LA, Lafayette Parish, LA, LaSalle Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Pointe Coupee Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint Helena Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Tensas Parish, LA, Washington Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Amite County, MS, Claiborne County, MS, Copiah County, MS, Covington County, MS, Forrest County, MS, Franklin County, MS, George County, MS, Greene County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Jefferson County, MS, Jefferson Davis County, MS, Jones County, MS, Lamar County, MS, Lawrence County, MS, Lincoln County, MS, Marion County, MS, Pearl River County, MS, Perry County, MS, Pike County, MS, Simpson County, MS, Stone County, MS, Walthall County, MS, Wilkinson County, MS

The watches that followed

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

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 0.1 hours before the alert went out and 105 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-pSkew-T log-p diagram, Slidell Radar S, LA at 00:00Z on 2017-01-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1796 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Slidell Radar S, LA at 00:00Z on 2017-01-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 288 square meters per square second.1939587897117136Sfc1 km3 km6 km9 kmRMLM
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
1796 J/kg
Mixed-layer CIN
-13 J/kg
Mixed-layer LCL
528 m above ground
0-6 km bulk shear
96 kt
0-1 km storm-relative helicity
288 m²/s²
0-3 km storm-relative helicity
382 m²/s²
Significant tornado parameter
4.0
Supercell composite
16.4

Open this sounding in Storm Lab

The text

As transmitted.

461 
ACUS11 KWNS 220006
SWOMCD
SPC MCD 220005 
ALZ000-MSZ000-LAZ000-220130-

Mesoscale Discussion 0097
NWS Storm Prediction Center Norman OK
0605 PM CST Sat Jan 21 2017

Areas affected...Southeast Louisiana/southern Mississippi and
vicinity

Concerning...Tornado Watch 15...

Valid 220005Z - 220130Z

The severe weather threat for Tornado Watch 15 continues.

SUMMARY...Severe/tornado threat is expected to steadily increase
over the next few hours in/near Tornado Watch 15.

DISCUSSION...Latest radar loop shows scattered strong/severe storms
increasing from the northwest Louisiana vicinity southeast across
the New Orleans area, near a warm front arcing
northwest-to-southeast across this region.  A moist/buoyant boundary
layer (dewpoints into the low 70s) continues to spread slowly
northward in conjunction with the advancing warm front, which should
remain a focus for continued convective development/increase over
the next several hours.

As the left exit region of a 100 kt mid-level jet streak spreads
eastward across the area and low-level winds likewise increase,
shear will favor intense/rotating updrafts.  This in conjunction
with backed surface flow near/just north of the warm front will
enhance the overall environment with respect to severe risk --
including the possibility for strong/long-lived tornadoes.  We will
continue to monitor northward progression of the warm front and
associated convective evolution, with an eye toward
future/additional tornado watch issuance north and east of WW 15
(into central Mississippi, central and southern Alabama, and
possibly parts of the Florida Panhandle).

..Goss.. 01/22/2017

...Please see www.spc.noaa.gov for graphic product...

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

LAT...LON   31958937 31208801 29718820 29498974 30049197 30849270
            32169205 32259082 31958937

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jan 21, 6:51 PM CSTTornado Watch PDSSPCAutauga, Baldwin, Barbour, Bibb, Bullock, Butler and 36 more8 hr
Jan 21, 8:30 PM CSTMesoscale DiscussionSPCAutauga, Baldwin, Barbour, Bibb, Bullock, Butler and 34 more90 min
Jan 21, 9:57 PM CSTMesoscale DiscussionSPCAutauga, Barbour, Bibb, Bullock, Butler, Chilton and 29 more93 min
Jan 21, 11:49 PM CSTMesoscale DiscussionSPCAutauga, Barbour, Bibb, Bullock, Butler, Chilton and 30 more116 min
Jan 22, 1:55 AM CSTMesoscale DiscussionSPCHenry, Houston65 min
Jan 22, 2:20 AM CSTTornado WatchSPCHenry, Houston9 hr
Jan 22, 2:46 AM CSTMesoscale DiscussionSPCBarbour, Bullock, Chambers, Clay, Coosa, Crenshaw and 9 more119 min
Jan 22, 5:34 AM CSTMesoscale DiscussionSPCHouston86 min
Jan 22, 7:43 AM CSTMesoscale DiscussionSPCBaldwin, Barbour, Butler, Clarke, Coffee, Conecuh and 9 more2 hr
Jan 22, 8:06 AM CSTTornado WatchSPCBaldwin, Butler, Coffee, Conecuh, Covington, Crenshaw and 8 more5 hr
Jan 22, 9:16 AM CSTMesoscale DiscussionSPCEscambia59 min
Jan 22, 11:02 AM CSTMesoscale DiscussionSPCGeneva, Houston58 min
Jan 22, 11:47 AM CSTTornado Watch PDSSPCAutauga, Barbour, Bullock, Chambers, Chilton, Coffee and 13 more7 hr
Jan 22, 12:31 PM CSTMesoscale DiscussionSPCBullock, Chambers, Elmore, Lee, Macon, Montgomery and 2 more59 min
Jan 22, 2:28 PM CSTMesoscale DiscussionSPCChambers, Clay, Lee, Randolph92 min
Jan 21, 7:50 PM CSTTornado WatchSPCCatahoula, Concordia, East Carroll, Franklin, Madison, Morehouse and 3 more4 hr
Jan 21, 8:14 PM CSTMesoscale DiscussionSPCEast Feliciana, Livingston, Saint Helena, Saint Tammany, Tangipahoa, Washington and 1 more61 min
Jan 21, 8:22 PM CSTMesoscale DiscussionSPCBienville, Caldwell, Catahoula, Claiborne, Concordia, East Carroll and 13 more113 min

Nearby

Mesoscale Discussions in Louisiana, 2017Mesoscale Discussions in Mississippi, 2017Mesoscale Discussions in Alabama, 2017Every mesoscale discussion in 2017

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.