Case Study: July 14, 1997Synoptic BackgroundOn July 14, 1997, the Toronto area was located in the warm sector of a weak surface low pressure system centered over Northern Ontario. A cold front extended from the low center southwest to the southern Plains. Through the day, the low and the cold front moved slowly eastward ahead of a 500 hPa trough centered over Minnesota. The cold front was just entering southern Ontario by early next day. Weak but broad regions of high pressure were centered over the central and south-eastern US. Air in the warm sector over southern Ontario was very warm and unusually moist. Maximum surface temperatures in the region reached 34°C while surface dew points locally exceeded 27°C at times. Surface winds were moderate from the southwest but veered to westerly above the boundary layer. A weak anticyclonic vortex was present at the 250hPa level over the Toronto area. Upper level winds were relatively light and variable with height. Lake BreezeA moderate westerly gradient wind was observed at the surface and resulted in the development of distorted lake breeze in the Toronto area. However, the true nature of the lake breeze has been difficult to characterize due to a sparseness of observational data, ambiguous satellite images and suspected urban frictional effects in the area. High-resolution MC2 modelling results are used here to illustrate the flow features. See section Output. |
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For problems or questions regarding this web site contact Xin Qiu [xinqiu@yorku.ca].Last updated: April 06, 1999. |