Bomb cyclone, medicane, polar vortex, oh my! Wondering what these crazy weather terms mean? You are not alone. Severe weather has its own strange vernacular that is becoming more prominent in today’s headlines. Although these terms have been around for a long time, recent weather events across the United States have popularized them.
Bomb Cyclone
Named by Fred Sanders and John Gyakum in a 1980 study, “bomb cyclone” refers to an intense storm where the barometric pressure drops rapidly over 24 hours producing high winds (central pressure decreases by at least 24 millibars in 24 hours). As the storm moves over coastal waters, it picks up moisture, resulting in heavy snow. In some areas, gusts can cause flooding more like those felt during a tropical storm.
Forecasters are on high alert when a bomb cyclone is likely because they can cause harmful impacts such as blizzards, severe thunderstorms and heavy precipitation. Bomb cyclones are large and intense midlatitude storms with low pressure at the center. It gets the name “bomb” from undergoing what is termed “bombogenesis.” This is when the colder air mixes with the warmer sea air, leading to a swift drop in atmospheric pressure.
The East Coast is one of the regions where bombogenesis is most common because there is a natural contrast between the cool land and the warm Gulf Stream current. Watch this video to learn the difference between the hurricanes we get on the Gulf Coast and a bomb cyclone further north.
Polar Vortex
“Polar vortex” is a relatively new weather term for winter weather forecasting. However, meteorologists have understood the concept for much longer. A polar vortex occurs when very cold air and a large low pressure system in the northern hemisphere is pushed down the North American continent, as far south as the Northeastern United States.
A polar vortex always exists near the poles, but we only hear about it in the winter because it weakens during the summer months and we typically only receive the Arctic air in the wintertime. Polar vortex conditions are observed at high altitudes in the atmosphere and do not exist on the Earth’s surface.
However, we can still feel the extremely cold air that is associated with them. Be sure to prepare for cold weather and have your home and car emergency kit ready if you are alerted to colder temperatures in your area.
Medicane
No, this is not a term describing a health care plan. As you might guess, the term “medicane” is a combination of two words: Mediterranean and hurricane. They are much like hurricanes but are geographically confined over the Mediterranean Sea and are surrounded by land.
Medicanes are rare (1-2 form per year) and have been known to develop within water temperatures of only 59° F while hurricanes require surface water temperatures to be warmer to form (79° F). Medicanes typically occur from September to December, just as the Gulf hurricane season is winding down.
Similar to a hurricane, the clouds of a medicane swirl around a central eye-like structure where the strongest part of the storm forms. Impacts from a medicane include flooding, mudslides, uprooted trees, fallen electrical poles and building wall failure.
Regardless of your weather expertise, understanding these odd terms can help you during your next stint on Jeopardy! or trivia night at your local hangout. Maybe when you are stuck in an airport flying home, and your flight is delayed due to a blizzard caused by a bomb cyclone, you can find some comfort in knowing the science behind it (just maybe).
For more information on severe weather, contact Tracie Sempier, VORTEX-SE engagement coordinator, at tracie.sempier@usm.edu.