Around September 20, a frontal boundary moved into eastward into the Atlantic ocean from North America. A well-defined non-tropical low formed along the boundary and passed north of Bermuda on September 23. Deep convection increased near the center over the next couple of days and the circulation separated from the front. The system was named Tropical Storm Isaac late on September 25 over the central tropical Atlantic.
Isaac rode the clockwise flow east-northeast around the north side of the subtropical ridge and encountered enough upper-level divergence and instability to support strengthening even over marginally warm sea surface temperatures. The storm reached hurricane status early on the 27th and an eye began to intermittently appear on satellite imagery.
Surprisingly, Isaac had a few more tricks up its sleeve, and intensified even further overnight. The eye became better defined and the surrounding area of convection larger and deeper. The storm peaked at category 2 strength on September 28 with peak winds of 105 mph and a central pressure of 968 mb. It turned northeast and began to pass over markedly colder water soon after. This began a period of gradual weakening, which brought Isaac back down to tropical storm strength by the evening of September 29, when it was passing northwest of the Azores. Beyond rough seas, there was no direct impact to the islands. Cold water and increasing shear brought about Isaac's transition to a post-tropical cyclone on September 30. The remnants continued northeastward until they dissipated west of Ireland.
The image above shows Isaac as a category 2 hurricane.
Isaac was impressively strong for its latitude, but did not affect any land areas.
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