Bloodstar
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Loc: Tucson, AZ
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Tropical Versus Sub Tropical
Thu Dec 01 2005 03:35 AM
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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: http://web.archive.org/web/20010813101211/www.atlantichurricaneguide.com/subtropical.html
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:
http://australiasevereweather.com/cyclones/2001/summ0106.txt
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)
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