Can two tropical cyclones merge to become a much bigger storm?

 

Laura and Marco are generating a lot of attention; not only about their development and track; but also, about what could happen to Laura and Marco if they meet and merge?

The press has been talking about it, many times not correctly. Social Media is flooded with talk about them becoming a giant hurricane, which is not true. It’s true there have never been two hurricanes in the Gulf at the same time; there is a good reason for this and that has to do with the size of the Gulf and available energy. While the Gulf of Mexico is very large, it’s small when talking about oceans. The gulf is about 930 miles wide. So, two hurricanes would have to stay well away from each other (like on opposite ends of the Gulf) If they were closer, they might compete for energy resources and kill off one or both of them. Being that far west or east would make for a lot of land interaction, which would be very detrimental for a hurricane to survive. While Marco’s and Laura’s tracks overlap in the Gulf possibly making landfall within miles and around 24-48 hours of each other, this doesn’t mean a super hurricane is going to happen.

As far back as the record goes, there hasn’t been two hurricanes in the Gulf of Mexico at the same time. But that doesn’t mean there haven’t been two tropical cyclones in the Gulf at the same time. In early September of 1933, two hurricanes were tracking toward the U.S. -- one dubbed the 1933 Cuba-Brownsville Hurricane (Hurricane 8) in the Gulf of Mexico headed toward Texas and the other (Hurricane 11) near the Bahamas, the Treasure Coast Hurricane, tracking toward the east coast of Florida. On Sept. 4, the Treasure Coast Hurricane made landfall as a Category 3 near the border of Palm Beach and Martin counties in Florida at the same time, the Cuba–Brownsville hurricane was slowly tracking toward Texas. Here is an old U.S. Weather Bureau weather map that shows this (courtesy of Philip Klotzbach). The storms made landfall within 24 hours of each other, But the Treasure Coast Hurricane weakened to a tropical storm over Florida before entering the Gulf. The other time was on June 18, 1959, during a brief time there were two tropical storms spinning over the Gulf simultaneously. One was Tropical Storm Beulah, the other was a newly formed tropical storm that would later develop into Hurricane Three.

Anyway, back to 2020, the year of the strange and unexpected….

Here is my latest answer on the idea of these two merging….

Laura and Marco won't as you say merge and combine forces to form a single larger and more powerful storm.

There are three scenarios that occur when tropical cyclones get close to each other. By close I mean within 190 miles of each other. That spacing will be hard to do in the Gulf, given it’s about 930 miles wide. But that be as it may.

The first scenario is, if they are around the same strength, and if Laura and Marco come in close enough proximity, they will dance and rotate counterclockwise around a common midpoint, otherwise known as the Fujiwhara effect. I covered the Fujiwhara Effect a couple of weeks ago during Friday weather school.

The second scenario is, if you have two hurricanes of the same relative strength in close proximity, then their respective sinking air can weaken both storms simultaneously.

The third scenario is, if one tropical cyclone is significantly stronger than the other tropical cyclone, then the weaker of the two can rotate into the stronger storm and weaken even more as it does so. The larger tropical cyclone absorbs the leftover moisture from its dying counterpart, though this absorption could make the parent larger, it does not make the larger parent storm any stronger.

So if any of y’all are thinking Category 6 out of some kind of collision, don’t hold your breath.