Initial investigation of observed stable-season Great Lakes sensible heat fluxes and cyclone evolution

Considerable research has been conducted on the tendency for cyclogenesis to occur over the Great Lakes during cold air outbreaks. Atmospheric instability generated by the relatively-warm lakes can result in considerable upward fluxes of sensible heat and moisture which, in turn, increases upward motions, cloud and precipitation development and ultimately the cyclone. Much less is known about the influences of the Great Lakes on passing cyclones during the stable season; the mechanisms for the observed increase in forward speed and intensification of cyclones during the stable season are not understood.

This study seeks to understand the relationships between surface sensible heat fluxes over the entire Great Lakes region and storm development during the months of May to July over a 10-year period. During those months, a total of 38 cyclone centers were found to move into the Great Lakes region and remain for at least 18 hours. For each of these cyclones, surface sensible heat fluxes were calculated from water and atmospheric observations taken at a total of eight buoys on the lakes, from 24 hours before the cyclone moved into the Great Lakes region to the time period when the cyclone departed the region.

Our preliminary investigation found that the central pressure of the cyclones tended to decrease with increasing total positive sensible heat fluxes and tended to increase with increasing total negative heat fluxes. Interestingly, there were greater increases in the forward motion of cyclones with increasing total positive OR negative sensible heat fluxes. Hypotheses for these findings and relationships between the fluxes and locations of storm movement through the Great Lakes region will be discussed.