Current Radar or Satellite Image - Central Florida Hurricane CenterHurricanes Without the Hype! Since 1995

The 2019 Atlantic Hurricane Season begins on June 1st, 2019 and ends on Nov 30th, 2019.
Days since last H. Landfall - US: Any 104 (Michael) , Major: 104 (Michael) Florida - Any: 104 (Michael) Major: 104 (Michael)
Login to remove ads


General Discussion >> Hurricane Ask/Tell

Jump to first unread post. Pages: 1

Reged: Mon
Posts: 441
Loc: Georgia Tech
Tropical Versus Sub Tropical
      #64113 - Thu Dec 01 2005 03:35 AM

Just because I want to, I am going to try to clarify Tropical Versus Sub-Tropical. If I have the facts off, would some of the mets please step in and correct, but here goes.

Firstly, A subtropical storm is one that encompasses both Tropical and non tropical aspects of the storm. Specificly, Subtropical storms are quantatively defined as being from a formerly nontropical Upper level low (hence the cold, versus Warm core). Additionally Subtropical storms have VERY large windfields that are strongest out hundred(s) of miles from the center.

Subtropcal storms can also spin up from Frontal boundries, but are typically smaller in size and scope (Mezoscale features is how they are referred to)

Tropical Storms are defined by their presistant convection near the center, a windfield that is strongest at the center. The storms get their energy from as a heat engine (which is the driving force behind warm core systems).

I remarked the night before Epsilon was upgraded that it looked like a small Tropical system in a larger subtropical environment. It probably would have been more precise to say that it was embedded in a Upper level Low. (though it's feasible to have 2 maxima, one near the center and one futher away, particularly since there could be both the warm core driving the center winds and the cold upper level winds driving the windfield at large distances from the center, but that's ambling futher and further off topic.

Storms don't have to 'look' tropical to be tropical. we use Satellite imagry as a guide, and they're a great help since ships and planes can't be everywhere. But just because a storm doesn't look like the 'classic' warm core tropical storm/hurricane doesn't make it not one. Certain tell tails do exist, when you see cloud formations associated with a cold core system (stratocumulus for one) wrapping into a tropical system, that's a good tell that the storm is transistioning into a cold core (extratropical) system.

Late season storms are a bit of a head scratcher. They tend to form in odd places, and when they do form, they're forming in typically marginal conditions. Don't let them fluster you.

An interesting read, and something for people who are curious about subtropical systems:

which details the case for 2 possible subropical systems to have affected Spain and Portugal in 2000.

here's some more information on tropical versus subtropical storms, in particular how some of the NHC/HPC view the differences:

I find it fascinating that evidently shallow warmcore systems qualify as a tropical rather than subtropical by the NHC. the quote that implies this: "In David's
opinion, the (usually) small cyclones sometimes seen in the Atlantic
(and also often in the Mozambique Channel) which may contain eye
features but have shallow convection and shallow warm cores with
cold cores aloft should be classed as subtropical rather than as
tropical cyclones."

Chances are this post has utterly lost everone, so I'll stop here, but I hope it helps clarify things a little

(Post moved to a more appropriate Forum)

Edited by Ed Dunham (Thu Dec 01 2005 08:41 AM)

Post Extras: Print Post   Remind Me!   Notify Moderator  
Senior Storm Chaser

Reged: Fri
Posts: 1191
Loc: Twin Cities
Re: Tropical Versus Sub Tropical [Re: Bloodstar]
      #64114 - Thu Dec 01 2005 09:47 AM

Well you know how to cruise the web! That was very revealing. And, it shows that the things that are question marks to us today were settled a long time ago at NHC; they are being consistent with their internal standard.

I'm trying to work out how this is justified. How about this reasoning. Because the storm is shallow, as long as it it warm-core up to the heights of the cloud tops, then it does not matter if it is still cold-core, higher up, because it is embedded in the larger low? It is embedded in a three-dimensional sense. However that doesn't seem totally logical.

Someone just pointed out to me something that can be demonstrated most clearly by a quote from the most recent discussion:


This is clearly IMHO code for subtropical cyclone. And I am ok with that as long as it works out everyone is on the same page.

Katrina's Surge:

Post Extras: Print Post   Remind Me!   Notify Moderator  

Reged: Mon
Posts: 441
Loc: Georgia Tech
Re: Tropical Versus Sub Tropical [Re: Margie]
      #64119 - Thu Dec 01 2005 03:09 PM

Good point. I think what is going on is based on windfield. I think if they're seeing a central area of high winds they're going ahead and declaring it a tropical system, despite the hybriid aspects that exist. Some of the forecasters there don't think that's entirely accurate, but they're going along with it for the sake of consistancy.

I'm just hypthosizing, but I think we're also having trouble with these storms because they are in a cyclonic envelope, which ruins a storms appearance, as the outflow has real issues getting developed in such an environment.

Anyway, hopefully this helps


M. S. Earth and Atmospheric Sciences, Georgia Tech - May 2019.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1

Extra information
0 registered and 6 anonymous users are browsing this forum.

Moderator:  CFHC, Ed Dunham, Colleen A., danielw, Clark, RedingtonBeachGuy, Bloodstar, tpratch, typhoon_tip, cieldumort 

Print Topic

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled

Topic views: 4686

Rate this topic

Jump to

Note: This is NOT an official page. It is run by weather hobbyists and should not be used as a replacement for official sources. 
CFHC's main servers are currently located at in Orlando, FL.
Image Server Network thanks to Mike Potts and Amazon Web Services. If you have static file hosting space that allows dns aliasing contact us to help out! Some Maps Provided by:
Great thanks to all who donated and everyone who uses the site as well. Site designed for 800x600+ resolution
When in doubt, take the word of the National Hurricane Center