Blocking high-pressure Over Ontario/Quebec Ahead of North Atlantic TC Activity Has Serious Implications

Problem…Blocking high-pressure over Ontario/Quebec ahead of North Atlantic TC activity. West-turning storms and storm stalls.

Fig. 1: GFS upper air forecast for August 30, 2022 indicates a high-pressure ridge block over Ontario/Quebec which will influence western North Atlantic TC’s.

Discussion: In late August, GFS indicates a titanic upper-level high-pressure ridge extending from the Great Lakes region to Quebec (Fig. 1). The upper-level ridge is well-correlated to very warm SSTA in the northwest North Atlantic basin (Fig. 2). The GFS indicates the tropical cyclone season finally gets underway the last week of August featuring a Cape Verde storm near Bermuda on Aug. 30^th and a second storm moving inland on the north-central Gulf of Mexico Coast. GFS projects 959 MB for the Bermuda event which indicates a potential major hurricane. The Gulf system is likely to reach hurricane strength moving across warm waters prior to reaching the coast. The GFS is a highly variable forecast model and these long-term storm projections are made with below average confidence. However, the more reliable concern here is evolution of the blocking ridge pattern which would provide steering currents to turn tropical cyclones into the East Coast (possibly as major hurricanes) and the stalling influence on Gulf Coast systems causing a deluge of heavy rain. Close monitoring of a potentially dangerous uptick in tropical cyclone activity is ahead.  

Fig. 2: The very warm ocean surface across the northwest North Atlantic basin is well-correlated to high-pressure aloft centered on the Great Lakes for late August.