Alert archive / Louisiana / Mesoscale Discussions in 2016

Mesoscale Discussion 657

May 19, 201616 parishes in Louisiana; 6 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at May 19, 2016, 10:22 PM CDT for 16 parishes in Louisiana; 6 counties in Mississippi. It was in force for 83 min.

The area

The outline as issued.

The facts

Issued: May 19, 2016, 10:22 PM CDT (03:22 UTC)
Expired: May 19, 2016, 11:45 PM CDT
In force: 83 min
Issued by: the Storm Prediction Center

All 22 counties

Ascension Parish, LA, Assumption Parish, LA, East Baton Rouge Parish, LA, Jefferson Parish, LA, Lafourche Parish, LA, Livingston Parish, LA, Orleans Parish, LA, Plaquemines Parish, LA, Saint Bernard Parish, LA, Saint Charles Parish, LA, Saint James Parish, LA, Saint John the Baptist Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Terrebonne Parish, LA, Washington Parish, LA, George County, MS, Hancock County, MS, Harrison County, MS, Jackson County, MS, Pearl River County, MS, Stone County, MS

The watches that followed

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

Severe Thunderstorm Watch 184May 19, 10:50 PM CDT

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 00:00Z, 3.4 hours before the alert went out and 13 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2145 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: -6 m²/s²
0-3 km storm-relative helicity: 48 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

As transmitted.

291 
ACUS11 KWNS 200323
SWOMCD
SPC MCD 200322 
ALZ000-MSZ000-LAZ000-200445-

MESOSCALE DISCUSSION 0657
NWS STORM PREDICTION CENTER NORMAN OK
1022 PM CDT THU MAY 19 2016

AREAS AFFECTED...SERN LA / SRN MS / MOBILE BAY

CONCERNING...SEVERE THUNDERSTORM WATCH 183...

VALID 200322Z - 200445Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 183
CONTINUES.

SUMMARY...THE POTENTIAL FOR ISOLATED WIND DAMAGE WILL CONTINUE
ACROSS SERN LA AND PROBABLY ACROSS COASTAL MS AND MOBILE BAY.  A
FAVORABLE ZONE FOR MESOVORTEXGENESIS MAY CONTINUE TO BE REALIZED
ALONG THE EFFECTIVE FRONT FROM NEAR LAKE PONTCHARTRAIN EASTWARD
ALONG THE MS GULF COAST.  A NEW SEVERE THUNDERSTORM WATCH MAY NEED
TO BE CONSIDERED BY 0400-0430Z FOR PORTIONS OF SRN MS AND SWRN AL.

DISCUSSION...RADAR IMAGERY SHOWS A SEVERE QLCS WITH A NOTABLE NRN
BOOK-END VORTEX 20 MI SW BTR.  A WEST-EAST ORIENTED EFFECTIVE FRONT
/ANALYZED VIA DEWPOINT GRADIENT AND STREAMLINES/ IS LOCATED FROM
NEAR THE WESTSIDE OF LAKE PONTCHARTRAIN EWD ALONG THE MS GULF COAST
INTO THE MOBILE BAY VICINITY.  ALONG THIS CORRIDOR...WEAK LOW-LEVEL
CONFLUENCE AND A MESOSCALE RIBBON OF STREAMWISE VORTICITY MAY BE
OCCASIONALLY TILTED INTO THE VERTICAL AND STRETCHED---LEADING TO
INTERMITTENT MESOVORTEXGENESIS.  THE KLIX VAD DATA HAS CHANGED
CONSIDERABLY THE LAST 2 HOURS WITH STRENGTHENING E TO SELY FLOW IN
THE LOWEST 1 KM.  THE VERY MOIST BOUNDARY LAYER WILL LIKELY SUPPORT
A CONTINUATION OF THE QLCS INTO SRN MS AND SWRN AL DURING THE LATE
EVENING TO OVERNIGHT HOURS.

..SMITH.. 05/20/2016

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

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

LAT...LON   30639119 31019013 30998853 30788819 28888855 28609102
            30639119

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 7:53 PM CDT	Mesoscale Discussion	SPC	Assumption, Iberia, Jefferson, Lafourche, Plaquemines, Saint Charles and 2 more	67 min
May 19, 8:10 PM CDT	Severe Thunderstorm Watch	SPC	Acadia, Ascension, Assumption, East Baton Rouge, Iberia, Iberville and 18 more	6 hr
May 19, 10:52 PM CDT	Severe Thunderstorm Watch	SPC	Forrest, George, Greene, Hancock, Harrison, Jackson and 5 more	6 hr
May 20, 1:26 AM CDT	Mesoscale Discussion	SPC	Wayne	2 hr
May 20, 2:33 PM CDT	Mesoscale Discussion	SPC	Lowndes	2 hr

Nearby

Mesoscale Discussions in Louisiana, 2016 Mesoscale Discussions in Mississippi, 2016 Every mesoscale discussion in 2016

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.