Case Study: July 2, 1997

Some nasty summer severe weather occurred on July 2, 1997, in southwestern Ontario and there was some speculation that lake breezes may have been involved. I decided to run MC2 for this day to assess the role of lake breezes. Indeed, the model predicts the development of 'high deformation' lake-breeze circulations. This type of lake breeze set-up (moderate S or SW surface winds with lake breezes and an approaching cold front) turns out to be rather important to summer severe weather forecasting and nowcasting in SW Ontario. Take a look for yourself! 

On this day, tornadoes occurring in central and southeastern Michigan produced heavy damage and several fatalities. A line of supercell thunderstorms formed just ahead of an unseasonably strong cold front during the afternoon hours. As the line of storms, including a tornado, passed across the Detroit River to northeast of Windsor, the tornado lifted. Wall clouds were still reported as a supercell storm crossed Essex County. A few weak tornadoes are thought to have developed as storms moved into Kent County.

The conditions on this day have been modelled using MC2 on a 5 km grid. There is no convective parameterization scheme available for this grid size so there are no precip data. The following are some results:

18 UTC - thunderstorms just beginning to pop up across central Michigan

Surface divergence and 10m winds - lake breeze front segments off SW corners of lakes

Vertical motion at 750 m with cross-section arrow

Cross-section through lake breeze fronts - take a look at those gravity waves!

1.5 m temperatures

1.5 m dew point temperatures

Boundary layer heights

MSL Pressure and 1000-500 mb thickness

21 UTC - storms moving into the Detroit area

Surface divergence and 10 m winds - lake breeze front segments now joined along Michigan coast

Vertical motion at 1000 m with cross-section arrow - lake breeze front north of Lake Erie too

Cross-section through lake breeze fronts - gravity waves still hangin' in there!

1.5 m temperatures - Detroit - Windsor in the hot zone

1.5 m dew point temperatures - lots of moisture too!

Boundary layer heights - big difference downwind of the lakes in southwestern Ontario

00 UTC on July 3rd - line of storms has moved off to the east

MSL Pressure and 1000-500 mb thickness - cold front moving through