Both hurricanes originated from similar large-scale circulations known as “Central American Gyres,” called that due to their broad sprawling nature and propensity to develop over Central America. October is the peak season for formation of these gyres. During the past few years, we have seen several tropical cyclones develop from these large systems. They also result in widespread heavy rainfall over the regions they traverse.
The origins of Michael can be traced to Oct. 3. It was born within a broad disturbance with multiple centers in the East Pacific and Caribbean Sea. This gyre had unleashed torrential rains over Central America, producing flooding and mudslides over Honduras, Nicaragua and El Salvador that killed at least 13 people.
As the gyre moved slowly to the northwest, thunderstorms focused on its northeastern side over the northwestern Caribbean. They resulted in the development of a smaller circulation that became Hurricane Michael. Tropical cyclones forming within these gyres is a common occurrence, especially along their northeastern side. In fact, this time last year, Hurricane Nate also formed within a gyre in the Caribbean.
The evolution from a gyre to Michael is remarkably similar to the weather pattern that resulted in Hurricane Opal. Like Michael, Opal began its life as a gyre, producing flooding rainfall over Mexico and Guatemala, killing 50 people as it very slowly moved toward the northwest.
As Hurricane Opal moved over the warm waters of the Gulf of Mexico, it rapidly intensified from a tropical storm into a Category 4 hurricane. Opal then made landfall in the Florida Panhandle as a Category 3 hurricane on Oct. 4, 1995. A particularly dangerous aspect of Opal was its storm surge, with the sea rising 8 to 14 feet east of the storm center as it came ashore. As much as $4.7 billion of damage was attributed to the storm.
Michael seems destined to follow in the footsteps of Opal, both with its similar formation, and now with its probable landfall point in the Florida Panhandle.
But why is Michael taking a track toward the Florida Panhandle? Let’s try to break down the relevant features controlling Michael’s track.
Two primary features are steering Michael toward the Florida Panhandle. A large upper-level trough or dip in the stream is located over the Rockies, and this feature is pushing Michael to the east-northeast. There is also a large ridge of high pressure off the southeastern U.S. coast, and this feature is pushing Michael toward the northwest. The combination of both features results in a primarily northward track toward the Florida Panhandle with a landfall most likely Wednesday afternoon or evening.
Unfortunately, Michael is now forecast to be even stronger than the intensity of Opal at landfall at 125 mph, meaning the devastating impact from the storm surge, strong winds and heavy rains may be even greater.