Alert archive / Michigan / Tornado Watches in 2013

Tornado Watch 124

April 18, 201336 counties in Michigan

The Storm Prediction Center issued this tornado watch at Apr 18, 2013, 10:06 AM EDT for 36 counties in Michigan. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Apr 18, 2013, 10:06 AM EDT (14:06 UTC)
Expired
Apr 18, 2013, 3:48 PM EDT
In force
6 hr
Issued by
the Storm Prediction Center
Largest hail expected
1.5 in
Strongest gust expected
70 kt
All 36 counties

Allegan County, MI, Barry County, MI, Bay County, MI, Calhoun County, MI, Clinton County, MI, Eaton County, MI, Genesee County, MI, Gratiot County, MI, Huron County, MI, Ingham County, MI, Ionia County, MI, Isabella County, MI, Jackson County, MI, Kalamazoo County, MI, Kent County, MI, Lapeer County, MI, Lenawee County, MI, Livingston County, MI, Macomb County, MI, Mecosta County, MI, Midland County, MI, Monroe County, MI, Montcalm County, MI, Muskegon County, MI, Newaygo County, MI, Oakland County, MI, Oceana County, MI, Ottawa County, MI, Saginaw County, MI, Saint Clair County, MI, Sanilac County, MI, Shiawassee County, MI, Tuscola County, MI, Van Buren County, MI, Washtenaw County, MI, Wayne County, MI

The radar

The Grand Rapids radar (KGRR), 76 km from the middle of the area, began a volume at 14:05 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
40%
One or more EF2 to EF5 tornadoes
20%
Ten or more severe wind reports
40%
One or more gusts of 65 knots or more
30%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
10%
Six or more combined severe hail and wind reports
95%

Warnings issued inside it

9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 18, 10:52 AM EDTSevere Thunderstorm WarningGRRAllegan, Van Buren53 min
Apr 18, 11:12 AM EDTSevere Thunderstorm WarningGRROttawa48 min
Apr 18, 1:50 PM EDTSevere Thunderstorm WarningDTXGenesee, Livingston, Oakland40 min
Apr 18, 2:11 PM EDTSevere Thunderstorm WarningDTXLapeer, Oakland49 min
Apr 18, 2:40 PM EDTSevere Thunderstorm WarningDTXSaint Clair, Sanilac50 min
Apr 18, 2:42 PM EDTSevere Thunderstorm WarningDTXWashtenaw, Wayne48 min
Apr 18, 2:49 PM EDTSevere Thunderstorm WarningDTXMacomb, Saint Clair56 min
Apr 18, 2:54 PM EDTSevere Thunderstorm WarningDTXMonroe51 min
Apr 18, 3:00 PM EDTSevere Thunderstorm WarningDTXOakland45 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Detroit, MI (KDTX), launched 12:00Z, 2.1 hours before the alert went out and 104 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-pSkew-T log-p diagram, Detroit, MI at 12:00Z on 2013-04-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 42 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Detroit, MI at 12:00Z on 2013-04-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 476 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
42 J/kg
Mixed-layer CIN
-226 J/kg
Mixed-layer LCL
609 m above ground
0-6 km bulk shear
64 kt
0-1 km storm-relative helicity
476 m²/s²
0-3 km storm-relative helicity
516 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.9

Open this sounding in Storm Lab

The text

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

306 
WWUS20 KWNS 181408
SEL4  
SPC WW 181408
MIZ000-LHZ000-LMZ000-182200-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 124
NWS STORM PREDICTION CENTER NORMAN OK
1010 AM EDT THU APR 18 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  SOUTHERN MICHIGAN
  LAKE HURON
  LAKE MICHIGAN

* EFFECTIVE THIS THURSDAY MORNING AND EVENING FROM 1010 AM UNTIL
  600 PM EDT.

* PRIMARY THREATS INCLUDE...
  SEVERAL TORNADOES POSSIBLE
  SEVERAL DAMAGING WIND GUSTS WITH A FEW SIGNIFICANT GUSTS TO 80
    MPH POSSIBLE
  A FEW LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 95 STATUTE
MILES EAST AND WEST OF A LINE FROM 15 MILES NORTHWEST OF SAGINAW
MICHIGAN TO 20 MILES SOUTHEAST OF JACKSON MICHIGAN.  FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 122...WW 123...

DISCUSSION...AS A WARM FRONT LIFTS NORTHWARD ACROSS THE
REGION...DESTABILIZATION WILL ALLOW FOR FURTHER INTENSIFICATION OF A
PRE-COLD FRONTAL SQUALL LINE RAPIDLY ADVANCING NORTHEASTWARD INTO
REGION.  DISCRETE SUPERCELL DEVELOPMENT ALSO APPEARS POSSIBLE WITH
THE RISK FOR TORNADOES AHEAD OF THE LINE...BEFORE IT MOVES EAST OF
THE WATCH AREA BY LATE THIS AFTERNOON.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 24050.


...KERR

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 18, 8:25 AM EDTMesoscale DiscussionSPCBerrien, Cass, Kalamazoo, Saint Joseph95 min
Apr 18, 9:31 AM EDTTornado Watch PDSSPCBerrien, Branch, Cass, Hillsdale, Saint Joseph7 hr
Apr 18, 9:48 AM EDTMesoscale DiscussionSPCAllegan, Barry, Bay, Calhoun, Clinton, Eaton and 29 more27 min
Apr 18, 12:14 PM EDTMesoscale DiscussionSPCBarry, Bay, Branch, Calhoun, Clinton, Eaton and 26 more2 hr

Nearby

Tornado Watches in Michigan, 2013Every tornado watch in 2013

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.