Severe Weather and Heavy Rain across Northern Michigan on 5/11

A complex of strong thunderstorms slowly moved through northern Michigan last Wednesday, bringing a variety of severe weather to the area ranging from high winds to large hail to flash flooding.  It was a very long duration event, as the complex entered eastern Upper Michigan around 8am, with thunderstorms still ongoing in Manistee and Wexford counties into the evening hours.

 

The first aspect of the severe weather event came to be during the late morning hours, as very strong winds developed behind the squall line as it weakened from north to south. The following are some of the storm reports our office received as a result of the strong winds yesterday. Note the most prevalant damage just south of the Sault Ste. Marie area.

 

..TIME..    ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE.. ....MAG.... ..COUNTY LOCATION.. ST.. ...SOURCE....
1056 AM     NON-TSTM WND GST SAULT STE. MARIE        46.48N 84.37W
05/11/2011 M55 MPH CHIPPEWA MI ASOS

MEASURED AT SANDERSON FIELD.
1100 AM     NON-TSTM WND DMG 6 SSW SAULT STE. MARIE  46.40N 84.41W
05/11/2011 CHIPPEWA MI PUBLIC

26 TREES REPORTED DOWN ON SOUTH MACKINAC TRAIL...BETWEEN
6 MILE AND 9 MILE ROADS. MOSTLY PINE TREES...20 TO 30
FOOT TALL. TIME IS ESTIMATED.


1100 AM NON-TSTM WND DMG 4 SE SAULT STE. MARIE 46.44N 84.31W
05/11/2011 CHIPPEWA MI PUBLIC

3 TREES UPROOTED...ONE 12 INCHES IN DIAMETER. ALSO
DAMAGE TO A GARAGE AND BARN. DAMAGE OCCURED DUE TO THE
PASSAGE OF A WAKE LOW.
0100 PM     NON-TSTM WND DMG BOYNE CITY              45.18N  84.96W
05/11/2011 CHARLEVOIX MI TRAINED SPOTTER

SEVERAL BRANCHES DOWN...PORTABLE CANOPY BLOWN AROUND 50
FEET.
0125 PM     NON-TSTM WND DMG VANDERBILT              45.14N  84.66W
05/11/2011 OTSEGO MI PUBLIC

12 TO 14 IN. DIAMETER FIR TREE SNAPPED IN HALF.

 

While most strong winds associated with thunderstorms occur out ahead, or under a storm, these strong winds trailed behind the thunderstorm area. These winds were attributed to what is known as a "wake low," a compact area of low pressure that sometimes forms on the back side of a decaying thunderstorm complex. These smaller scale features can lead to rapid barometric pressure falls, which in turn causes the atmosphere to respond by dramatically strengthening the winds; the winds blow from higher pressure ahead of the storm, to the lower pressure following behind. In this particular case, the pressure difference was substantial enough to cause damage.

 

While most of the thunderstorm complex continued to fall apart as it rolled into northeast Lower, thunderstorms continued to gather strength over Manistee and Wexford counties. The storms continued to back build over Lake Michigan, pushing inland and over these same areas through the afternoon and evening hours. This effect, known as "training" of thunderstorms, caused some very hefty rainfall totals across Wexford and Manistee counties, with anywhere between 4 to 7 inches of rain falling in as little as 8 hours! The heaviest rain occurred over the southern half of Manistee County, where numerous road closures were reported, including portions of US-31 and M-22. Below are some of the rainfall reports received by our office for this event.

 

..TIME..    ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE.. ....MAG.... ..COUNTY LOCATION.. ST.. ...SOURCE....
..REMARKS..

0900 PM HEAVY RAIN 1 N WELLSTON 44.23N 85.95W
05/11/2011 M5.05 INCH MANISTEE MI CO-OP OBSERVER

12 HOUR TOTAL THRU 9 PM.
0915 PM     HEAVY RAIN       MANISTEE                44.24N  86.33W
05/11/2011 M4.44 INCH MANISTEE MI TRAINED SPOTTER

12 HOUR TOTAL THRU 9 PM.

1000 PM HEAVY RAIN 5 SSW BRETHREN 44.23N 86.06W
05/11/2011 M4.65 INCH MANISTEE MI TRAINED SPOTTER

24 HR TOTAL THRU 10 PM. PEA SIZED HAIL FELL AROUND 1
PM...HALF-INCH DIAMTER HAIL FELL AROUND 5 PM.
1000 AM     HEAVY RAIN       2 SW CADILLAC           44.23N 85.44W
05/12/2011 M1.85 INCH WEXFORD MI CO-OP OBSERVER
24 HOUR TOTAL THRU 8 AM.

Finally, large hail was reported with the storms over Manistee and Wexford Counties. While most of the hail reports received by our office were around one quarter to one half inch, we did receive a couple of reports of half dollar and ping pong sized hail over parts of Manistee County Wednesday afternoon.



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