JACKSONVILLE – Another subtropical cyclone formed today marking the fourth time this season a tropical system acquired hybrid structures.
Ernesto developed over cool water about 700 miles southeast of Newfoundland Wednesday with all the hallmarks of classic subtropical systems which have been so common this year.
Dry air, cool water and high upper level winds have hindered pure tropical low pressure systems only to favor types of storms that resemble mid-latitude or extratropical storms.
Hurricane Chris bucked the trend but Alberto, Beryl, Debby, and now Ernesto all acquired a mix of upper level cold core temperatures along with low level warm center.
This characteristics will also include winds reaching farther from the center than a typical tropical system and this often prevents subtropical storms from rapidly intensifying.
Subtropical systems can transition into full blown tropical cyclones like Debbie did off west of the Azores in early August or as we saw with Hurricane Beryl, fall apart into remnants only to regenerate with the help of upper level upper energy. This was the case when Beryl reformed as a subtropical storm south of Bermuda in July.
Often upper-level troughs prevent hurricanes due to hostile shear but can contribute enough energy to the system to overcome cool surface water in higher latitudes.