Alert archive / Alabama / Mesoscale Discussions in 2007

Mesoscale Discussion 2004

September 21, 200720 counties in Alabama

The Storm Prediction Center issued this mesoscale discussion at Sep 21, 2007, 8:57 PM CDT for 20 counties in Alabama. It was in force for 93 min.

The area

The outline as issued.

The facts

Issued: Sep 21, 2007, 8:57 PM CDT (01:57 UTC)
Expired: Sep 21, 2007, 10:30 PM CDT
In force: 93 min
Issued by: the Storm Prediction Center

Counties Autauga County, AL, Bibb County, AL, Butler County, AL, Chilton County, AL, Choctaw County, AL, Clarke County, AL, Conecuh County, AL, Dallas County, AL, Escambia County, AL, Greene County, AL, Hale County, AL, Lowndes County, AL, Marengo County, AL, Monroe County, AL, Perry County, AL, Shelby County, AL, Sumter County, AL, Tuscaloosa County, AL, Washington County, AL, Wilcox County, AL

The radar

The Birmingham radar (KBMX), 102 km from the middle of the area, began a volume at 02:00 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 watches that followed

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

Tornado Watch 683Sep 21, 10:10 PM CDT

The nearest sounding before it

Birmingham, AL (KBMX), launched 00:00Z, 2.0 hours before the alert went out and 102 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: 336 J/kg
Mixed-layer CIN: -3 J/kg
Mixed-layer LCL: 823 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 153 m²/s²
0-3 km storm-relative helicity: 144 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.

000 
ACUS11 KWNS 220157
SWOMCD
SPC MCD 220157 
ALZ000-FLZ000-MSZ000-220330-

MESOSCALE DISCUSSION 2004
NWS STORM PREDICTION CENTER NORMAN OK
0857 PM CDT FRI SEP 21 2007

AREAS AFFECTED...CNTRL AND SRN AL...WRN FL PANHANDLE

CONCERNING...TORNADO WATCH 681...

VALID 220157Z - 220330Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 681 CONTINUES.

THE TORNADO THREAT WITH TROPICAL DEPRESSION 10 SHOULD GRADUALLY
SPREAD NWWD INTO WRN AND CNTRL AL. ORGANIZATION AROUND THE SYSTEM
AND LOW-LEVEL SHEAR PROFILES SHOULD BE ADEQUATE TO CONTINUE A
TORNADO THREAT. A TORNADO WATCH SHOULD BECOME NECESSARY ACROSS THE
REGION TONIGHT.

THE CENTER OF TROPICAL DEPRESSION 10 IS CURRENTLY JUST EAST OF
MOBILE AL AND DISTINCT SPIRAL BANDING IS EVIDENT ON RADAR ACROSS SE
AL AND THE WRN FL PANHANDLE. THE LATEST DIAGNOSTIC DATA SHOWS A
POCKET OF PRECIPITABLE WATER VALUES GREATER THAN 2.25 INCHES JUST
NORTH OF THE CENTER SUGGESTING RAINBANDS WILL CONTINUE TO FORM
AROUND THE NORTH SIDE OF THE CENTER LATE THIS EVENING INTO THE
OVERNIGHT PERIOD. SUFFICIENT INSTABILITY AND STRONG LOW-LEVEL SHEAR
PROFILES SHOWN ON REGIONAL WSR-88D VWPS SHOULD CONTINUE TO BE ENOUGH
FOR A TORNADO THREAT WITH ROTATING STORMS AS THE RAINBANDS MOVE NWWD
INTO CNTRL AND WRN AL OVERNIGHT. SEVERAL CONFLUENCE BANDS JUST
NORTHEAST OF THE CENTER ACROSS SE AL APPEAR TO BE DEVELOPING AND
THESE RAINBANDS SHOULD HAVE THE GREATEST POTENTIAL FOR ROTATING
STORMS.

..BROYLES.. 09/22/2007

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

ATTN...WFO...BMX...MOB...JAN...

33678731 33448802 32458843 31088823 30648749 31008667
32408635 33368664

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 21, 10:11 PM CDT	Tornado Watch	SPC	Autauga, Baldwin, Barbour, Bullock, Butler, Chambers and 23 more	6 hr
Sep 22, 2:00 AM CDT	Mesoscale Discussion	SPC	Baldwin, Clarke, Conecuh, Covington, Escambia, Mobile and 2 more	2 hr

Nearby

Mesoscale Discussions in Alabama, 2007 Every mesoscale discussion in 2007

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.