Weather Blog: A 'tropical storm' in April?

By Brian McClure, Bay News 9 Meteorologist
Last Updated: Friday, April 21, 2017, 12:19 PM EDT

On Thursday, a sub-tropical depression way out in the northeast Atlantic was declared “Tropical Storm Arlene."

Before anyone gets carried away and starts worrying, this storm is not a threat anywhere.  

Secondly, it's formation has no relevance to the upcoming tropical season. 

Really a "tropical storm"?

Honestly, it’s debatable if "Arlene" is even a “tropical storm”.  It formed in an area where there is a larger non-tropical regular low pressure area that has a cold front and warm front attached to it.  

The other issue is that it formed in an area of the cool north Atlantic where the current water temperature is only 64 degrees.  Research done by numerous scientists over the years has proved that a purely tropical system needs warm water to a certain depth in the ocean of about 78 degrees and above, and for a strong tropical storm to survive the water actually needs to be 80 degrees.  



And yet another issue: Arlene formed in a region that never had satellite coverage until very recently in the modern era. Quite honestly, our satellites weren’t even that great at detecting high resolution features like this until really recent times.  

Therefore, don’t stress too much when you hear someone yell loudly and hype that “this is only the second time ever that an April tropical storm has formed!!”   

That statement should really come with a huge asterisk that states: “this is the second time in the past 20 years that our modern-day satellites have detected a low pressure in the Atlantic that had the appearance of a tropical storm, but isn’t purely tropical”.  

For example, the other time we made record of this was in 2003 when Sub-tropical storm Ana formed east of Bermuda.  It also had a nice swirl, but just didn’t have the pure characteristics of a tropical storm.  

Nobody made a big deal about it because it was before the onslaught of social media, where things now spread like wildfire.

Effect on records

The main problem with naming these odd storms is that our historical records will now be skewed.  Before modern-day satellites, we didn’t see any of these odd little low pressures out in the middle of nowhere.  

With that in mind, we can’t realistically compare our records over the past 100 years, because this is the type of storm that never would have been on the record books.  

On any given day, we see things on our new satellites that are really cool and unique.  

We discuss these interesting things during our weather casts and sometimes show them on our website and social media sites.

We believe in stating facts and showing everyone what we’re seeing, but we don’t believe in hype and blowing things out of proportion.