Alert archive / Ohio / Mesoscale Discussions in 2012

Mesoscale Discussion 1703

August 4, 201219 counties in Indiana; 20 counties in Michigan; 44 counties in Ohio

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2012, 7:23 PM EDT for 19 counties in Indiana; 20 counties in Michigan; 44 counties in Ohio. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 4, 2012, 7:23 PM EDT (23:23 UTC)
Expired: Aug 4, 2012, 9:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 83 counties

Adams County, IN, Allen County, IN, Blackford County, IN, DeKalb County, IN, Delaware County, IN, Elkhart County, IN, Grant County, IN, Howard County, IN, Huntington County, IN, Jay County, IN, Kosciusko County, IN, LaGrange County, IN, Miami County, IN, Noble County, IN, Randolph County, IN, Steuben County, IN, Wabash County, IN, Wells County, IN, Whitley County, IN, Allegan County, MI, Barry County, MI, Branch County, MI, Calhoun County, MI, Cass County, MI, Eaton County, MI, Hillsdale County, MI, Ingham County, MI, Jackson County, MI, Kalamazoo County, MI, Lenawee County, MI, Livingston County, MI, Macomb County, MI, Monroe County, MI, Oakland County, MI, Saint Clair County, MI, Saint Joseph County, MI, Van Buren County, MI, Washtenaw County, MI, Wayne County, MI, Allen County, OH, Ashland County, OH, Auglaize County, OH, Champaign County, OH, Clark County, OH, Coshocton County, OH, Crawford County, OH, Cuyahoga County, OH, Darke County, OH, Defiance County, OH, Delaware County, OH, Erie County, OH, Franklin County, OH, Fulton County, OH, Hancock County, OH, Hardin County, OH, Henry County, OH, Holmes County, OH, Huron County, OH, Knox County, OH, Licking County, OH, Logan County, OH, Lorain County, OH, Lucas County, OH, Madison County, OH, Marion County, OH, Medina County, OH, Mercer County, OH, Miami County, OH, Morrow County, OH, Ottawa County, OH, Paulding County, OH, Putnam County, OH, Richland County, OH, Sandusky County, OH, Seneca County, OH, Shelby County, OH, Summit County, OH, Union County, OH, Van Wert County, OH, Wayne County, OH, Williams County, OH, Wood County, OH, Wyandot County, OH

The radar

The Detroit radar (KDTX), 115 km from the middle of the area, began a volume at 23:26 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.

Severe Thunderstorm Watch 561Aug 4, 7:50 PM EDT

The nearest sounding before it

Detroit, MI (KDTX), launched 12:00Z, 11.4 hours before the alert went out and 117 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: 79 J/kg
Mixed-layer CIN: -100 J/kg
Mixed-layer LCL: 1364 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: -15 m²/s²
0-3 km storm-relative helicity: -15 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.

713 
ACUS11 KWNS 042323
SWOMCD
SPC MCD 042323 
OHZ000-MIZ000-INZ000-050130-

MESOSCALE DISCUSSION 1703
NWS STORM PREDICTION CENTER NORMAN OK
0623 PM CDT SAT AUG 04 2012

AREAS AFFECTED...PORTIONS CENTRAL/NRN INDIANA...SRN LOWER
MI...LE...WRN/NRN OH.

CONCERNING...SEVERE THUNDERSTORM WATCH 559...

VALID 042323Z - 050130Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 559
CONTINUES.

SUMMARY...WW MAY BE CLEARED BEHIND MAIN MCS THAT WAS MOVING EWD
40-45 KT ACROSS SWRN LOWER MI AND NRN INDIANA AS OF 23Z.  ADDITIONAL
WW AND/OR COUNTY EXTENSIONS OF WW 559 MAY BE REQUIRED E OF PRESENT
CONFIGURATION.

DISCUSSION...MAIN MCS IS SUPPORTED BY STG LOW-LEVEL COLD POOL WITH
2-4 MB PER 2 HR ISALLOBARS IMMEDIATELY BEHIND MAIN PRECIP
AREA...THEN WAKE DEPRESSION OF SIMILAR NEGATIVE MAGNITUDES. 
THERMODYNAMIC ANALYSES AND MODIFIED FCST SOUNDINGS SUGGEST PATCHY
BUT MOSTLY FAVORABLE SUPPORT ACROSS REMAINDER SRN LOWER MI...NERN
INDIANA ND NWRN OH.  SRN PORTION OF COMPLEX IS OVERTAKING
ADDITIONAL/RELATIVELY DISCRETE CONVECTIVE ELEMENTS FORMING IN WARM
SECTOR...WHERE 2000-3000 J/KG MLCAPE IS EVIDENT.  AS THIS PART OF
COMPLEX ENTERS OH...IT WILL MOVE INTO AREAS AT LEAST TEMPORARILY
STABILIZED BY SECONDARY TSTM BAND DESCRIBED BELOW. 
HOWEVER...MOIST/SSWLY-SWLY FLOW FROM SFC TO 850 MB WILL SUPPORT AIR
MASS RECOVERY INTO NWRN OH.  CORRIDOR OF ENHANCED MIDLEVEL FLOW --
RELATED TO MCV OVER SRN WI -- IS ENHANCING DEEP SHEAR ACROSS NRN
INDIANA AND SERN LOWER MI...WITH WSWLY EFFECTIVE SHEAR VECTORS OF
30-40 KT. 

MIXED SIGNALS LEND UNCERTAINTY TO MAINTENANCE OF THAT PART OF MCS
OVER EXTREME NRN INDIANA AND SRN LOWER MI...BUT ANOTHER WW STILL MAY
BE NEEDED FARTHER E TOWARD SERN LOWER MI.  HIGH THETAE ALSO IS
EVIDENT ACROSS SRN LOWER MI...WITH 70S F SFC DEW POINTS AND 1.5-1.75
INCH PW.  NRN PORTION OF MCS WILL INTERACT WITH WEAKER/NON-SVR NWRN
EXTENSION OF OH CONVECTION BEFORE ENCOUNTERING THAT AIR
MASS...THOUGH STRENGTH OF COLD POOL MAY BE MAINTAINED THROUGH
RELATIVELY STABLE CORRIDOR JUST E OF MI SEGMENT OF MAIN MCS. 

SECONDARY BAND OF STG-SVR TSTMS WILL MOVE ENEWD ACROSS PORTIONS NRN
ON IN REGIME OF FAVORABLE BUOYANCY AND WEAK CINH FOR A FEW MORE
HOURS...BUT MODEST DEEP-LAYER FLOW AND SHEAR.  FCST SOUNDINGS
SUGGEST 70S F SFC DEW POINTS WILL SUPPRESS RATE OF DIABATIC SFC
COOLING AND HELP TO MAINTAIN 1500-3000 J/KG MLCAPE THROUGH AT LEAST
02Z.  THEREAFTER...STABILIZATION WILL BE GRADUAL...WHILE LEADING
EDGE OF ACTIVITY CONTINUES TO LIFT PARCELS VIA FORCED ASCENT.  MAIN
CONCERN WILL BE DAMAGING GUSTS.

..EDWARDS.. 08/04/2012

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

ATTN...WFO...PBZ...CLE...ILN...DTX...IWX...GRR...IND...

LAT...LON   39838399 40368626 41038613 42028602 42598678 43148248
            42838246 42538259 42618264 42698267 42648281 42538284
            42408288 42328302 42168313 41998315 41828339 41718344
            41528287 41388246 41508198 41718129 40508152 40108195
            39788391 39838399

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 4, 2:13 PM EDT	Mesoscale Discussion	SPC	Brown, Crawford, Daviess, Dubois, Floyd, Gibson and 14 more	92 min
Aug 4, 2:46 PM EDT	Severe Thunderstorm Watch	SPC	Benton, Jasper, Lake, Newton, Porter	4 hr
Aug 4, 4:57 PM EDT	Mesoscale Discussion	SPC	Benton, Carroll, Cass, Elkhart, Fulton, Howard and 19 more	63 min
Aug 4, 5:35 PM EDT	Severe Thunderstorm Watch	SPC	Adams, Allen, Blackford, Cass, DeKalb, Elkhart and 18 more	5 hr
Aug 4, 7:50 PM EDT	Severe Thunderstorm Watch	SPC	Wayne	5 hr

Nearby

Mesoscale Discussions in Ohio, 2012 Mesoscale Discussions in Michigan, 2012 Mesoscale Discussions in Indiana, 2012 Every mesoscale discussion in 2012

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.