Waterspout on Lake St. Clair on July 3

A waterspout was sighted between around 8:40 and 9:00 am on Lake St. Clair near the Wayne/Macomb County Line.  Waterspouts form when an updraft vertically stretches an area of cyclonic rotation or shear at the surface.  These updrafts are associated with unstable air, which results from cool air flowing over warmer waters.  Waterspouts in the Great Lakes are more common in the fall months when the lakes are at their warmest, but they can occur during the summer months.  (Click images for larger versions)


Climatology of waterspouts in the Great Lakes (from Wade Szilagyi, http://www.vos.noaa.gov/MWL/dec_04/waterspout.shtml)


The necessary ingredients for waterspout formation were in place on the morning of July 3.   First, a seasonably cool airmass was in place, with 850 mb temperatures (about 1 mile above ground level) of 9 degrees C observed on the morning sounding from White Lake, which was below the 25th percentile for June.  Meanwhile, water temperatures on Lake St. Clair were around 21 degrees C, resulting in a vertical temperature difference of 12 degrees C.  The sounding also indicated plenty of moisture in the low levels.  The 12Z (8 am EDT) surface analysis showed an east/west-oriented surface trough axis near Lake St. Clair (dashed line):

12Z (8 am EDT) 3 July 14 Surface Analysis (left) and White Lake, MI sounding (right)


Cyclonic flow was evident in the 9 am surface observations near Lake St. Clair.  Note the westerly winds at Detroit City Airport (left side of screen), and the easterly winds at Selfridge ANGB (top of screen).  Also of note is the area of cyclonic shear picked up by the DTX radar.  Red colors indicate motion away from the radar, while green colors indicate motion toward the radar.  The reflectivity image shows a shower in the vicinity of the waterspout that had developed near Detroit and intensified as it moved over the warmer waters of Lake St. Clair.


902 am 0.5 degree velocity (left) and reflectivity (right) with 9 am surface observations


The updraft associated with the shower was able to stretch a portion of the area of cyclonic shear vertically and produce a waterspout.  Here are some pictures of the waterspout submitted to us, along with links to video:


Credit: Will Cyr (left) and Cathy DeNardis McIntosh (right)

Video courtesy Scott Bedker

Video via ClickOnDetroit


By Dan Thompson, Meteorologist, National Weather Service Detroit/Pontiac


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