A summary of seasonal forecasts of North Atlantic basin tropical cyclone activity issued initially in April and updated in June and August by the Tropical Meteorology Project at Colorado State University, Tropical Storm Risk of U.K. and Climate Impact Company indicate each revision is slightly more active due to less inhibiting upper shear due to a weakening El Nino (compared to early forecasts) coupled with a warmer than normal North Atlantic basin especially just north of the tropics.

Evolution of a super high latitude/high pressure blocking pattern is forecast to develop this weekend and next week in the southern hemisphere. The result is a negative Antarctic oscillation (-AAO) which goes “off the charts” to values near -6 according to some forecast models.

The polar ice cap has constricted to 80% of the 1980-2010 climatology and rivals July 2012. The European heat wave has ended however the warmth shifts north and strikes Greenland this week accelerating ice melt.

We now have 3 tropical waves in the outer tropical North Atlantic basin. Each tropical wave is located over 80-81F water which is marginally supportive for development. The upper shear axis stretches across the southern Caribbean Sea and northwest of the tropical waves. However, the shear axis is not particularly strong. Meanwhile upper shear is very light across the northern Caribbean Sea and Bahamas (where surface water is generally warmer than normal).