Alert archive / Arkansas / Mesoscale Discussions in 2011
Mesoscale Discussion 2000
The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2011, 7:41 AM CDT for 17 counties in Arkansas; 7 counties in Mississippi; 5 counties in Missouri. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 18, 2011, 7:41 AM CDT (12:41 UTC)
- Expired
- Aug 18, 2011, 10:15 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
All 29 counties
Baxter County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Fulton County, AR, Greene County, AR, Independence County, AR, Izard County, AR, Jackson County, AR, Lawrence County, AR, Lee County, AR, Phillips County, AR, Poinsett County, AR, Randolph County, AR, Sharp County, AR, St. Francis County, AR, Woodruff County, AR, Douglas County, MO, Howell County, MO, Oregon County, MO, Ozark County, MO, Ripley County, MO, Coahoma County, MS, DeSoto County, MS, Panola County, MS, Quitman County, MS, Tallahatchie County, MS, Tate County, MS, Tunica County, MS
The radar
The Memphis radar (KNQA), 110 km from the middle of the area, began a volume at 12:41 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.
The nearest sounding before it
Little Rock, AR (KLZK), launched 12:00Z, 0.7 hours before the alert went out and 120 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
- 2202 J/kg
- Mixed-layer CIN
- -101 J/kg
- Mixed-layer LCL
- 1370 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 79 m²/s²
- 0-3 km storm-relative helicity
- 62 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.8
The text
As transmitted, in the capitals the NWS used until 2016.
819
ACUS11 KWNS 181242
SWOMCD
SPC MCD 181241
TNZ000-ARZ000-MSZ000-MOZ000-181515-
MESOSCALE DISCUSSION 2000
NWS STORM PREDICTION CENTER NORMAN OK
0741 AM CDT THU AUG 18 2011
AREAS AFFECTED...PORTIONS SRN MO...NRN/ERN AR...EXTREME SWRN
TN...NWRN MS.
CONCERNING...HEAVY RAINFALL
VALID 181241Z - 181515Z
POTENTIAL EXISTS FOR MERGER OF CONVECTIVE CLUSTERS OVER DISCUSSION
AREA THAT THEN WOULD MOVE/SPREAD SEWD THROUGH AT LEAST
15Z...RESULTING IN EXPANSION OF AREA OF 2-3 INCH/HOUR RAIN RATES IN
HEAVIEST CORES. SHORTER-LIVED EPISODE OF SIMILAR RATES IS LIKELY AT
ANY GIVEN LOCATION AFFECTED BY NEARBY BAND OF TSTMS MOVING EWD ABOUT
20 KT ACROSS OZARKS OF S-CENTRAL MO AND EXTREME NRN AR.
FAVORABLE CAPE AND LIKELIHOOD OF DENSE PRECIP LOADING ALSO MAY
SUPPORT LOCALIZED POTENTIAL FOR DAMAGING WET DOWNBURSTS...BUT
PRIMARY THREAT APPEARS TO BE FROM HEAVY RAIN.
INITIALLY SEPARATE/MESOBETA-SCALE MULTICELLULAR TSTM COMPLEXES HAVE
DEVELOPED OVER PORTIONS NERN AR--
1. BAND OF TSTMS LOCATED BETWEEN SGT-ARG..EXPANDING IN COVERAGE AND
MOVING SEWD ABOUT 20 KT...AND
2. SOMEWHAT LESS-INTENSE BUT WELL-DEFINED CLUSTER INITIALLY FROM MEM
AREA NNWWD TOWARD JBR AND NWD TO JUST S OF MO BOOT-HEEL. CELLS IN
THIS COMPLEX ARE MOVING SSEWD...BUT OVERALL CLUSTER IS BACKBUILDING
SWWD TOWARD POTENTIAL MERGER ZONE WITH WRN COMPLEX.
PRIND MERGER WILL OCCUR THROUGH 14Z FROM PORTIONS POINSETT/CROSS
COUNTIES SSEWD OVER DELTA ADJACENT TO NRN PORTIONS MS/AR BORDER.
MEANWHILE MO/AR BORDER-AREA BANDS WILL PROCEED EWD ACROSS UNO AREA.
VERY MOISTURE-RICH ENVIRONMENT IS EVIDENT...BASED ON 12Z SGF RAOB
THAT SAMPLED UPSTREAM 850-MB TRAJECTORIES...YIELDING PW BETWEEN
2-2.25 INCHES...MEAN MIXING RATIO NEAR 19 G/KG AND MUCAPE OVER 4000
J/KG. PW APPEARS SOMEWHAT UNDER-REPRESENTED IN OBJECTIVE/RUC-BASED
MESOANALYSES OVER SRN MO BASED ON THAT RAOB...BUT APPEARS REASONABLE
FARTHER SE OVER ERN AR.
..EDWARDS.. 08/18/2011
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PAH...MEG...JAN...LZK...SGF...
LAT...LON 34479109 35489161 36639276 37129295 37089179 36899077
35959033 35278998 34588990 33959001 33889071 34179110
34479109SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 18, 1:04 PM CDT | Mesoscale Discussion | SPC | Adams, Amite, Claiborne, Clarke, Copiah, Covington and 34 more | 116 min |
| Aug 18, 2:40 PM CDT | Mesoscale Discussion | SPC | Bollinger, Cape Girardeau, Madison, Mississippi, Perry, Scott and 2 more | 2 hr |
| Aug 18, 2:51 PM CDT | Mesoscale Discussion | SPC | Atchison, Holt, Nodaway, Worth | 84 min |
| Aug 18, 6:00 PM CDT | Mesoscale Discussion | SPC | Andrew, Atchison, Bates, Benton, Buchanan, Caldwell and 21 more | 60 min |
| Aug 18, 6:18 PM CDT | Mesoscale Discussion | SPC | Atchison, Holt | 27 min |
| Aug 18, 6:38 PM CDT | Tornado Watch | SPC | Andrew, Atchison, Daviess, DeKalb, Gentry, Harrison and 3 more | 5 hr |
Nearby
Mesoscale Discussions in Arkansas, 2011Mesoscale Discussions in Mississippi, 2011Mesoscale Discussions in Missouri, 2011Every mesoscale discussion in 2011
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.