Columbus (WCMH) – Hermine is back over the water again, now in the Atlantic Ocean. It doesn’t look as impressive on satellite images, but it’s still packing quite a punch.
Hermine is now classified as a “post tropical cyclone” and unless you are a true weather enthusiast, you might not know what that is.
So let me explain…
- first off a closed low that spins counter-clockwise in the northern hemisphere is considered a cyclone.
- a Tropical Cyclone is a warm core system, that is not associated with a front, that forms over waters, tropical or sub-tropical waters. Tropical cyclones get their energy from heat taken from the waters below it.
- a Tropical Cyclone with winds of 38mph or less, it can be classified as a Tropical Depression
- when a Tropical Depression has sustained winds of 39mph or more, it is named and classified as a Tropical Storm
- when a Tropical Storm hits winds at 74mph that storm becomes a Hurricane
- if a Tropical Cyclone is north of the equator, but west of the International Date Line, it is a Typhoon
So what is a Post Tropical Cyclone?
When a storm starts to lose its tropical characteristics the storm may be classified as a post-tropical cyclone. Now it is important to note, this does not make the storm any less dangerous. In fact, Post Tropical Cyclones, like Hermine, can actually carry winds of Hurricane force. Hermine is forecast to have winds by Labor Day back above 74mph.
Now a Post Tropical Cyclone can be classified as two different types of lows, remnant lows and extratropical lows.
A remnant low is one that does not have the thunderstorm organization required to be classified to be a tropical storm. Also, the storm has winds less than the Tropical Storm threshold of 39mph. These occur when storms move into the North Atlantic, and appear on satellite as a swirling low, but with a lack of convection.
An Extratropical low, is a cyclone that has lost tropical characteristics, or did not have them. This type of cyclone gets its energy from the difference in temperatures between air masses vs. heat from the water as in a Tropical Cyclone. Extratropical Cyclones can possess winds in excess of 39mph (Tropical Storm force) and can have hurricane force winds as well.Bottom line:
If you are ever near the coast and any type of wind, surf, or flooding warnings are issued for a system, take the warnings seriously. No matter what the cyclone is called, it can still pack quite a wind, rain, and flooding punch.
If you have any questions about tropics, cyclones, extra tropics, or any other types of weather, send me an email dmazza@wcmh.com
-Dave
