Alert archive / Mississippi / Mesoscale Discussions in 2003

Mesoscale Discussion 77

February 15, 20036 parishes in Louisiana; 17 counties in Mississippi

The Storm Prediction Center issued this mesoscale discussion at Feb 15, 2003, 1:48 PM CST for 6 parishes in Louisiana; 17 counties in Mississippi. It was in force for 117 min.

The area

The outline as issued.

The facts

Issued: Feb 15, 2003, 1:48 PM CST (19:48 UTC)
Expired: Feb 15, 2003, 3:45 PM CST
In force: 117 min
Issued by: the Storm Prediction Center

All 23 counties

East Feliciana Parish, LA, Livingston Parish, LA, Saint Helena Parish, LA, Saint Tammany Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Amite County, MS, Covington County, MS, Forrest County, MS, Jasper 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, Smith 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 7Feb 15, 3:05 PM CST

The nearest sounding before it

Slidell Radar S, LA (KSIL), launched 12:00Z, 7.8 hours before the alert went out and 108 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: 48 J/kg
Mixed-layer CIN: -195 J/kg
Mixed-layer LCL: 605 m above ground
0-6 km bulk shear: 51 kt
0-1 km storm-relative helicity: 145 m²/s²
0-3 km storm-relative helicity: 184 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

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

033 
ACUS11 KWNS 151949
SWOMCD
SPC MCD 151948 
LAZ000-MSZ000-152145-

MESOSCALE DISCUSSION 0077
NWS STORM PREDICTION CENTER NORMAN OK
0148 PM CST SAT FEB 15 2003

AREAS AFFECTED...SE LA AND SRN/CNTRL MS

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 151948Z - 152145Z

TRENDS ARE BEING MONITORED FOR POSSIBILITY OF INCREASING SEVERE
THREAT.



CLUSTER OF CONVECTION CONTINUES TO SLOWLY INCREASE IN COVERAGE
OVER THE LOWER MISSISSIPPI VALLEY.  ACTIVITY APPEARS TO HAVE
INITIATED IN RESPONSE TO AREA OF STRONGER LOW-LEVEL WARM
ADVECTION...WELL IN ADVANCE OF MAIN UPPER TROUGH STILL LOCATED
OVER TEXAS AND THE NORTHERN MEXICAN PLATEAU.  AGEOSTROPHIC
FORCING IN ENTRANCE REGION OF 250 MB JET STREAK MAY HAVE ENHANCED
DIVERGENT UPPER FLOW FIELD ACROSS THE LOWER MISSISSIPPI VALLEY
PAST FEW HOURS...BUT THIS FORCING IS PROGGED TO CONTINUE
DEVELOPING RAPIDLY EAST NORTHEASTWARD THROUGH PARTS OF THE
TENNESSEE VALLEY/SOUTHERN APPALACHIANS THIS AFTERNOON.



DESPITE UNCERTAINTY WITH LARGER-SCALE FORCING...SUB SYNOPTIC
SURFACE LOW HAS BECOME EVIDENT PAST FEW HOURS IN ASSOCIATION WITH
STRONGEST CONVECTION OVER SOUTH CENTRAL LOUISIANA.  GIVEN
MODERATE INFLOW OF MOIST AIR MASS WITH UPPER 60S SURFACE DEW
POINTS OFF THE GULF OF MEXICO...SURFACE-BASED INSTABILITY WITH
CAPE AROUND 1000 J/KG MAY BE SUFFICIENT TO MAINTAIN VIGOROUS
THUNDERSTORMS THROUGH THE AFTERNOON HOURS.  THOUGH THERMODYNAMIC
ENVIRONMENT DOES NOT APPEAR PARTICULARLY SUPPORTIVE OF STRONG
DOWNDRAFTS...CONVECTION IS EMBEDDED WITHIN 40 TO 50 KT
SOUTHWESTERLY MID-LEVEL FLOW.  THIS WILL ENHANCE STORM MOTION AND
PROVIDE CONTINUING POTENTIAL FOR DAMAGING WIND GUSTS...WHICH MAY
AT TIMES APPROACH SEVERE LIMITS...AS CONVECTIVE SYSTEM ADVANCES
NORTHEASTWARD ACROSS SOUTH CENTRAL MISSISSIPPI INTO THE MERIDIAN
AREA BY 16/00Z.

..KERR.. 02/15/2003

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

30809117 31269095 31629063 32219002 32308878 31628867
30988899 30568958 30189042 30359096

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 15, 3:05 PM CST	Tornado Watch	SPC	Washington	6 hr
Feb 15, 5:51 PM CST	Mesoscale Discussion	SPC	Washington	114 min
Feb 15, 5:18 PM CST	Mesoscale Discussion	SPC	Lowndes	117 min

Nearby

Mesoscale Discussions in Mississippi, 2003 Mesoscale Discussions in Louisiana, 2003 Every mesoscale discussion in 2003

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.