Are Super-Storms Meteorologically Possible?

Many of today's sci-fi and disaster films include plots where hurricanes merge into one super-storm. But what would happen if two or more storms actually did collide? Believe it or not, this can and does occur in nature (although not on a scale that impacts the entire globe) and albeit rare. Let's look at several examples of these types of interactions.

The Fujiwhara Effect

Named for Dr. Sakarei Fujiwhara, the Japanese meteorologist who first observed the behavior, the Fujiwhara effect describes the orbiting of two or more weather features that are in close proximity to each other. Ordinary low-pressure systems typically interact when they're 1,200 miles or less from meeting. Tropical cyclones and hurricanes can interact whenever the distance between them is under 900 miles. This can happen when they form very near to each other or are steered on an intersecting path by upper-level winds. 

So what happens whenever storms collide? Do they merge into one big super-storm? Do they damage each other? In the Fujiwhara effect, the storms "dance" around the common mid-point between them. Sometimes this is as far as the interaction goes. At other times (especially if one system is much stronger or larger than the other), the cyclones will eventually spiral in towards that pivot point and merge into a single storm.

Examples include:

• During the 1995 Atlantic hurricane season, Hurricane Iris interacted with Hurricane Humberto, then interacted with and absorbed Tropical Storm Karen.
• In the fall of 2005, Hurricane Wilma absorbed Tropical Storm Alpha shortly after crossing south Florida and the Florida Keys. 

The Fujiwhara effect tends to involve systems that rotate, but cyclone s don't only interact with other cyclones. 

The Perfect Storm

One of weather history's most famous examples of weather features joining together is the East Coast's 1991 "Perfect Storm," the result of a cold front that exited the U.S. East Coast, a large low just east of Nova Scotia, and Hurricane Grace   

Superstorm Sandy

Sandy was the most destructive storm of the 2012 Atlantic hurricane season. Sandy merged with a frontal system just a few days before Halloween, hence the name "superstorm." Just days earlier, Sandy had merged with an arctic front pushing south across Kentucky, the result of which was over a foot of snowfall in the eastern part of the state and 1-3 feet across West Virginia. 

Since the merging of fronts is how nor'easters are normally born, many began calling Sandy a nor-eastercane (nor'easter + hurricane). 

Updated by Tiffany Means

Resource

Annual Summary of the 1995 Atlantic Hurricane Season