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Humid Subtropics


NC_Palms
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Is the humid subtropical climate of the Southeastern United States a true subtropical climate for being in temperate/middle latidutes or is a branch of the temperate climate dispite its name? 

Thank you

Zone 8a Greenville, NC 

Zone 8b/9a Bluffton, SC

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I assume your going off this map? screen-shot-2016-08-27-at-11-02-51-pm.pn

If that's the case then the answer would be "mostly true". Most of that green area in the map is indeed humid and almost tropical. However a lot of that I would personally consider borderline, if not outright temperate or tropical.  The northern edges of the green section are the most obvious. North Texas and Oklahoma are both hot and dry, while Maryland, Delaware, and Kentucky are too cold in the winter to be subtropical in my opinion.

Also the area around Brownsville Texas is pretty much tropical if memory serves me correctly. I would think a better boundary for the humid subtropics would be from Central Texas, across the deep south states, then up the coast to Virginia Beach. Nothing north of Arkansas or the Appalachian Mountains would be included. Otherwise a a general rule of them the map is pretty good as far as growing palm trees go. 

Edited by ThePalmNovice
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NC Palms, this subject is something that has intrigued me for the last several years and if you ever have time to take a look onto the City-Data weather forum, there is plenty of heated debate on this subject.

The southeastern United States exhibits a pretty unique humid-subtropical climate. As I said before, there are many different opinions on this, but I think the SE U.S. exhibits a humid subtropical climate with continental influences- although I wouldn't say it's a branch of a temperate climate. I think this subtropical area would start much further south than the map above. I like to take into account topography and eco-regions when it comes to defining subtropical climates. As for the SE U.S., I'd say the "true" subtropics start right where the piedmont ends, and the coastal plains begin. Here, humidity is oppressive in the summertime and the low altitudes (unlike piedmont areas, Atlanta, Charlotte, Birmingham, part of Columbia, Raleigh) along with the proximity to the ocean largely, if not totally contribute to this.

If I were to draw out a line of the subtropics in the southeast, it would include most, but not all of the Atlantic coastal plain from the very southeastern tip of Virginia Beach and south, widening to the boundary of the piedmont and coastal plain in North Carolina all along the southeast into South Carolina and into Georgia. Once you get into Alabama and Mississippi it gets a bit tricky due to being completely susceptible to cold shots and lack of protection from the Appalachian mountains, but I'd define the subtropics in Alabama and Mississippi starting in 8B regions and south.

Even if you look at broadleaf evergreen vegetation in the Southeast, the majority of these evergreens begin roughly at this line I speak of. It roughly starts at 8A/8B in the southeast.

 

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Pretty accurate, although the parts in the extreme north are a bit exaggerated. Once you get past Northern Virginia, that is about when the subtropics end. 

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PalmTreeDude

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On 5/21/2017, 4:49:43, ThePalmNovice said:

I assume your going off this map? screen-shot-2016-08-27-at-11-02-51-pm.pn

If that's the case then the answer would be "mostly true". Most of that green area in the map is indeed humid and almost tropical. However a lot of that I would personally consider borderline, if not outright temperate or tropical.  The northern edges of the green section are the most obvious. North Texas and Oklahoma are both hot and dry, while Maryland, Delaware, and Kentucky are too cold in the winter to be subtropical in my opinion.

Also the area around Brownsville Texas is pretty much tropical if memory serves me correctly. I would think a better boundary for the humid subtropics would be from Central Texas, across the deep south states, then up the coast to Virginia Beach. Nothing north of Arkansas or the Appalachian Mountains would be included. Otherwise a a general rule of them the map is pretty good as far as growing palm trees go. 

Brownsville Texas may just miss tropical. If we are doing this based on the latitudes where it is considered to be tropical and subtropical, we got this all wrong. But there are other factors that change weather or not a place is a certain climate. For example, in Southeast Florida it is technically not tropical, because the Tropic of Cancer does not run through it, but Floridas tropical waters regulate it so it is basically tropical. I posted a picture of the latitudes. 

IMG_0323.PNG

PalmTreeDude

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The winter-time variation in the US subtropical climates is seen as a feature of continentality, but many actual continental climates around the world don't really have much variation in winter temps either...

Note: I notice that this forum gets quite dead during the warmer months, compared to the winter (at least regarding posters from the Northern Hemisphere).

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  • 3 weeks later...

My yard feels like the Epicenter of the HUMID sub-tropics right now .  

Not so much actual accumulation of rain , really , here so far , but the dew points stay at    75 + /-   .

 

 

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Pretty much anywhere south of the 35 degree North latitude mark is a warm growing zone, for example, Virginia Beach is a cooler 8a then Columbia S.C. which is South of the 35 degree and is a warm 8a. 

PalmTreeDude

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  • 2 months later...

Personally I consider the Virginia coastal plain and it's Cheasapeake coastline the start of the subtropics. Southern Delaware and the coastal plain of Maryland is very similar to the rest of the Southeast in its forest types but it's winters are no different then the northeast. I would say the subtropics would end near Martin County, Florida where it will become the tropics as Brownsville, Texas seems transitional of the tropics and subtropics due to winter freezes. 

Zone 8a Greenville, NC 

Zone 8b/9a Bluffton, SC

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  • 3 weeks later...
On 5/21/2017, 3:49:43, ThePalmNovice said:

I assume your going off this map? screen-shot-2016-08-27-at-11-02-51-pm.pn

If that's the case then the answer would be "mostly true". Most of that green area in the map is indeed humid and almost tropical. However a lot of that I would personally consider borderline, if not outright temperate or tropical.  The northern edges of the green section are the most obvious. North Texas and Oklahoma are both hot and dry, while Maryland, Delaware, and Kentucky are too cold in the winter to be subtropical in my opinion.

Also the area around Brownsville Texas is pretty much tropical if memory serves me correctly. I would think a better boundary for the humid subtropics would be from Central Texas, across the deep south states, then up the coast to Virginia Beach. Nothing north of Arkansas or the Appalachian Mountains would be included. Otherwise a a general rule of them the map is pretty good as far as growing palm trees go. 

Being a Brownsville native, I personally think that the city deserves a tropical climate classification. To be specific, a tropical savannah climate. Granted, it does get cold at times, so were the lower RGV to be given that classification, it would qualify by just a hair. Nevertheless, in my eyes, the lower Rio Grande Valley is more tropical than it is subtropical. Like mentioned, not a GENUINE tropical, but simply a borderline tropical. Data used in Wikipedia for the city of Brownsville puts the city at a mere 2 or 3 degrees short of tropical climate classification. However, it's important to note that these numbers were taken from the years of 1981-2010. While a thirty year period is more or less a good period of time to calculate climate, the data from this period of time includes numbers from historic freezes, such as those of 1989 and 1983. But they're called HISTORIC for a good reason — they're rare. Such historic events don't rightly portray the climate of a certain area. Apart from possible misleading numbers, the area has physical proof of a tropical climate. Flora is nearly non-refutable testimony of Brownsville's tropical characteristics. Wide varieties of palm trees (Cuban Royals, Queen, Washingtonia, Foxtail, Sabal, Sago, etc) exist down here, & even coconut palms can be found sporadically. Royal poinciana (Flamoyant / Flame trees) and Ficus are widely seen as well. Apart from these, fruits can be grown like crazy too. I've personally seen the following fruits in properties within southern Cameron county: lime, aloe, pomegranate, pineapple, papaya, tamarind, mango, guava, banana, fig, watermelon, orange, grapefruit, corn, sugarcane, and sometimes avocado, grape, and apple. Certainly such fruit require warmth to flourish, and evidently Brownsville has enough of it to offer. For these reasons I believe that the lower Rio Grande Valley should properly be considered borderline tropical.  

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I agree, the Rio Grande Valley along with northern Tamaulipas is a transitional zone. Many plants of tropical origin (Cordia, Leucaena, Acacia, Amyris, etc) reach their northern limit in the area. But the area falls short of a tropical climate because hard freezes can and do occur from time to time. The 2011 winter wrecked all the tree sized Ficus benjamina in the area and caused most other Ficus, Delonix regia, etc to freeze back. It was a miracle that some coconuts survived. In fact, I don't think you are in the tropics until about 23*N in Tamaulipas...there is just nothing to stop the arctic air. 

 

 

 

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Jonathan

Katy, TX (Zone 9a)

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