Severe Weather August 2, 2015

Overview

Multiple rounds of severe weather impacted northern Michigan on August 2nd, 2015. The first severe thunderstorm warning was issued 10:34 am with an additional 27 warnings being issued before the last warning of the day expired at 8:00 pm. 4.25" hail observed seven miles north of West Branch was the largest documented hail stone ever to impact northern Michigan since records began in 1950.

Northern Michigan experienced a complex severe weather setup, which began with a warm front lifting northward from southern Michigan toward the Straits of Mackinac and into the eastern upper penninsula. This allowed for moisture to increase across the entire lower penninsula, which was evident by mid-60 degree dew points across much of northern Lower Michigan. The following image is a depiction of deep moisture, or Precipitable Water (PWAT), analyzed by the Storm Predicition Center at 21z (5:00 pm EDT).

In addition to ample moisture, the atmosphere had become extremely unstable. One frequently used variable to assess atmospheric instability is Surface Based Convective Available Potential Energy (SBCAPE). While values greater than 1000 J/kg may be sufficient to support strong-severe thunderstorms, the following image of SBCAPE analyzed by the Storm Prediction Center at 20z (4:00 pm EDT) indicates values between 2000-3500 J/Kg across portions along and south of M-32.

In a typical severe weather scenario, an ingredient known as wind shear is needed to support long-lived convection. Wind shear is the change in wind speed and/or direction with height in the atmosphere. As one might suspect, August 2nd was no different. Values greater than 35-40 kts are most supportive of organized severe weather.


NWS Gaylord Doppler Radar Reflectivity 8:00 am - 8:00 pm	SPC Mesoanalysis: Precipitable Water (in.) at 5 pm EDT	SPC Mesoanalysis: Surface Based Convective Available Potential Energy (SBCAPE) (J/Kg)

Wind & Hail

Wind & Hail:

Wind

Thousands of downed trees and power lines were reported on Sunday as 60-80 mph (locally 90-100 mph) straight-line winds accompanied the severe thunderstorms.


Shelf cloud near Kalkaska - Courtesy of Jason Mroz	Shelf cloud over Grand Traverse Bay - Courtesy of Kimberley Hankamp-Kroupa	Damage in Glen Arbor - Courtesy of Glen Arbor Artisans / Paul May	Mammatus Clouds in Onekema - Courtesy of Edward Bradford

Hail

The largest hail reported was 4.25", or the size of a softball, seven miles north of West Branch at 4:55 pm. The large hail was reported by trained spotters and members of the public. There were several reports of damage to vehicles and other property. At the time of the event, a Severe Thunderstorm Warning was in effect for all of Ogemaw County, issued at 4:33 pm. Additional reports of 1.00" to 2.00" hail were received from law enforcement, emergency managers, trained spotters and the public across multiple locations in northern Michigan.


Large Hail	Baseball to Softball sized hail - 7 miles north of West Branch - Photo Courtesy of Shelley Evergreen	Large Hail - Moorestown - Courtesy of Brent Morey	Large Hail - South Higgins Lake - Courtesy Lori Ritter

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