What’s up with the “sub”?

Posted at 8:12 AM, May 28, 2018

Subtropical Storm Alberto formed on May 25th (2018) in the western Caribbean Sea. We have had many viewers asking, “What is a subtropical storm?”

To quote a viewer email from Kevin…

“What is this crap about a subtropical storm. It either is or isn’t. No name until it is a tropical storm. I guess you are in cahoots with insurance companies to name a storm before it is so they won’t have to pay the first 2 percent of a claim for a named storm. Shame on you.”

  • First, It’s not “crap”, it’s meteorology.
  • Yes, it is or isn’t. A tropical vs subtropical are two different things (just like depression vs storm vs hurricane).
  • False, subtropical storms do get names (a subtropical depression would get a number).
  • No, we are not “in cahoots” with insurance companies (I am here to inform and educate, not to sell you a policy).
  • Shame on me?!? Remember, we don’t make the weather…

So, what is a subtropical storm?

According to NOAA, “A sub-tropical cyclone is a low-pressure system existing in the tropical or subtropical latitudes (anywhere from the equator to about 50°N) that has characteristics of both tropical cyclones and mid-latitude (or extratropical) cyclones.”

Subtropical cyclones (depressions or storms) are typically associated with an upper-level low-pressure system and have colder temperatures aloft. Tropical cyclones are warm-core from top to bottom and upper-level high-pressure systems helping their intensification.

Subtropical storms typically have a radius of strong winds farther out (60-125 miles from the center) than what is typically observed in tropical systems.

Many times subtropical storms can transform into tropical cyclones. A recent example is Hurricane Otto in October 2010.

Prior to 2002 subtropical storms were not given names. Gustav (2002) was the first subtropical storm to be named.

Sub or not, both types of systems can bring rain, wind, storm surge, flooding, and a risk for embedded tornadoes. Different titles but similar threats.