Is the climate of the southeast really an inferior/not a true subtropical climate? (perfect, northern)

[Can't think of username]

Originally Posted by Phil75230

Humid Subtropical (Cfa) is just a catch-all category: Too cold to be tropical, too warm to be continental.

Somebody tried the Jaunary 50F (10C) isotherm, would would be at the northern boundary of the FL Panhandle, but even this has problems.

Going east, it continues on that line to just west of the Okefenokee Swamp, then slants NE, hitting the Atlantic around Charleston. Going west, it basically follows latitude 31N (the N boundary of the "toe" of the Louisiana boot) and continues westward to -- somewhere between Waco and Austin.

Still, this puts Dallas and central Georgia in the same category as NYC and St Louis (on the Miss River, the January 32F(0 C) line. This also is absurd.

The best I can come up with is "3 months from 32-50F / 0-10C". That puts the line at about 100 miles north of Dallas, then going east to Little Rock and Memphis. BTW St Louis has either 4 or 5 months from 32-50F / 0-10C.

On the East Coast, I think, but not sure, that would put the boundary somewhere around Norfolk.

This is the best I can come up with: Split Cfa into three zones. Subtropical, mild-to-cool winter temperate, cool-but-not-cold winter temperate.

The thing about Cfa is that it works because the climates all tend to have comparable air flow from nearly continental Wichita to quintessential Dallas to nearly tropical Brownsville. Uniting them allows us to recognize how comparable air flow can give us a wide range of climates.

Even beyond that, you can see another generally similar pattern in all 3. In one of the many gone threads I listed, the user pdw made a comment that these Cfa climates all seem to follow a pattern dominated towards one thing but being able to see some notable changes the other way, like their poleward counterpart the subarctic climates.
That domination is warmth/heat compared to the equal, 4 season nondominant continental climates to the north and the always warm/hot tropical climates to the south. Wichita-Dallas-Brownsville are all warm-hot dominated but of course can see notable deviations from that, as you might expect from climates with comparable air flow.

[Can't think of username]

I am in the process of making some 2014-2023 climate normals for FSU Tallahassee (and they will be annually updated when fully ready).
Compared to the 'artificial Archbold' airport, they lack a ton of things that lead a lot on this thread to consider the Southeast US inferior. It can basically be summarized as their clay soil simultaneously reducing extreme heat at the same time as reducing cool and cold on clear, calm nights and their cold air drainage doing nothing to increase heat, which gets right to the heart of the matter of those on the inferior side.

A climate box is worth a thousand descriptive comments, so I won't say much more until those normals are ready. But this is the preview!

[Can't think of username]

In the meantime of making those FSU Tallahassee normals, I think I will reflect on how this past winter has caused me to refine my Southeast US priorities.

-First and foremost, I think I prioritize first and last frost monitoring over winter heat monitoring. Not only do I like monitoring for a big unbroken streak more than some hot days that will never realistically come in such a streak no matter how numerous they are, I have seen plenty of it during the 3 winters I have under my belt despite the comparative lack of good frost monitoring, so I've already had a good taste of it.

-This also extends to a usual lowest temperature of the season being at or above the usual minimum for the same applicable reason (comparative lack of seeing it in person, as all 3 winters under my belt had very unusual cold lows despite their heat).

-Tallahassee airport itself is a great example of a case where a sacrifice of monitoring heat allows me to have good frost and seasonal low results, if we compare this infamously warm February 2023 to infamously cold February 2015.
This February was 24.5C/10.8C (+5.3C) with a maximum of 31C (+4.1C) and minimum of 1C (+5.2C), while February 2015 was 17.4C/4.1C (-1.7C) with a maximum of 24C (-2.9C) and minimum of -6C (-1.8C).

But boy was the sacrifice worthwhile! February 2015 of course was the coldest air of the season (giving Tallahassee airport a +0.6C for the usual winter minimum), and the fact that it happened in February allowed the cold-following-blowtorch phenomenon typical of the Southeast allowed a fabulous February 20 last frost followed by a +3.4C March with the warmest March minimum on record (+3.6C).

This didn't just end with winter on March 20 either. It was so well timed that on its heels came a +4.2C record warm April which mind blowing could not begin to describe. The average low was +6.7C up from April and 1.5C up from May, with the monthly minimum of 13C being 1.6C higher than the average low, 4C warmer than the May minimum, and as warm as the average low on April 23!
For reference that would be like Toronto (known for its crappy Aprils) having an April with an average low of 8.5C and never getting below 3.5C the whole month followed by a May with a -0.5C frost!

Considering how garbage the Tallahassee airport's performance was this season (which being a very artificially cold microclimate won't change) like I outlined in the frost thread, I'd take a cooler 2015 analogy for my Southeast US list that didn't do well this season over a warmer 2023 analogy any day.

-This season has also helped me refine my ideal for places on my list (save for the cooler ones usually north of I-20). I monitor them November through March, but the bare minimum good first and last frosts I'd like are December 1 and February 28/29 (to give me a month of safe monitoring for first and last frosts), and the ideals are December 20-23 or later first frost (to be on or after the winter solstice) and February 20-23 or earlier last frost (so my winter solstice criteria can give me a total of at least 3 months of safe monitoring, also inspired to an extent by Tallahassee airport's February 20 2015 last frost).

-Last but not least, the final thing this season has taught me is to appreciate Gainesville even more, I think the airport will take Tallahassee airport's monitoring place. It has almost all of the same allure Tallahassee has of being a non stereotypical Florida location with much cooler winters compared to say Key West, but unlike Tallahassee airport the average frost dates (February 24 and December 4) are actually good and they have performed spectacularly both seasons I monitored them.

Last season was January 18 first frost with a lucky 1C on March 13 meaning a February 15 last frost, and this season will be December 23-January 28. And it was actually pretty close to the usual seasonal minimum of -5.1C too (-5C this winter and -6C before), likely due to the fact that it is not as prone to radiational cooling as other cold holes (January 30 2022 and March 16+20 this year show that) while also having a low latitude that lets it be 2C or so warmer than say Jacksonville during advective cold (March 13 and December 24 2022) and get off easy.
As a matter of fact it seems to be the only place on the entire Southeast list that met ALL the criteria of above average temperatures all around and good frost monitoring this season

[Can't think of username]

I finished those FSU normals! For comparison here are the 2014-2023 normals of KTLH to compare.

One thing that immediately stands out is KTLH being 1.2C warmer for the 2014-2023 normals than it is for 1991-2020. This a) makes me glad that I made 2014-2023 normals because comparing 1991-2020 normals to 2014-2023 would be misleading due to the difference, and b) makes me wonder what full 1991-2020 normals for FSU would be if we had them, given how much KTLH warmed up.

For further comparisons that can't be made with the boxes only, here are first and last frosts within that time period with total number of frosts:

2014-15:
KTLH November 2-February 20, 25 frosts
FSU November 19-February 20, 7 frosts

2015-16:
KTLH December 20-February 28, 14 frosts
FSU January 24

2016-17:
KTLH November 20-March 16, 11 frosts
FSU January 8-9

2017-18:
KTLH December 9-March 15, 23 frosts
FSU January 2-18, 8 frosts

2018-19:
KTLH November 28-March 6, 15 frosts
FSU no frost

2019-20:
KTLH December 3-February 28, 13 frosts
FSU January 21-22

2020-21:
KTLH December 1-March 9, 21 frosts
FSU December 1-27, 4 frosts

2021-22:
KTLH November 23-March 13, 17 frosts
FSU January 30

2022-23:
KTLH October 20-March 21, 13 frosts
FSU December 23-26

And frost free season length by full calendar year:

2015: KTLH 302 days, FSU 337 days
2016: KTLH 266 days, FSU 349 days
2017: KTLH 267 days, FSU 357 days
2018: KTLH 257 days, FSU 732 days
2019: KTLH 270 days, FSU 732 days (ongoing from 2018)
2020: KTLH 276 days, FSU 313 days
2021: KTLH 258 days, FSU 399 days
2022: KTLH 220 days, FSU 326 days

FSU beats out KTLH so bad it's just plain comical. The winter with the most frosts has 3 less than KTLH's least, and the shortest frost free season is longer than KTLH's longest by 11 days.

Now for how I believe this will help solve the 'inferior' dilemma some users have that this thread is all about.
Just as I was outlining in older comments, it has much warmer lows and seasonal minima in the cool season due to that wet clay soil and cold air drainage. It also has colder average highs, usual monthly maxima, and record highs in every single month because that wet clay is poor for heating up compared to sand - which helps solve the problem of excess heat that is also behind the inferior premise.
In short, the 2 main features behind the inferior premise are reduced notably compared to the airport.

One final thing I think is interesting to note is that just like those studies have found, the disparity between the 2 is nearly nonexistent during the warm/wet summer season (June-September). Looks like they were pretty spot on about the wet season eliminating the radiational cooling and soil moisture differences.

All things considered I find this a fascinating comparison between 2 polar opposites in a climate that gets almost all its heating and cooling from radiation during a substantial portion of the year. During the sunny day the solar radiation heats up the dry sand of KTLH more because the cold-reducing wet clay and cold air drainage of FSU is either inferior for or does nothing to help KTLH-style solar heating, but during night the opposite is true - almost all nights being clear and calm and almost all frost being produced by radiational cooling means the significant topography differences have a chance to consistently shine.

Bonus fun fact: the October 20 2022 freak KTLH frost that got me on the hunt for better stations actually lead me to put 2 and 2 together with regards to some things.
Before March 29 1961, records for Tallahassee were taken outside of KTLH. And with regards to October frosts is where the difference is most glaring - there were literally none recorded before the switch to KTLH, the lowest being 1C in 1952! It seems like the ones that were recorded after that were only because of radiational cooling, which not only makes sense for an artificially cold Archbold analogue but explains just why there weren't any before - outside KTLH obviously isn't very prone to radiational cooling.

I think it is fairly safe to say that outside of artificial KTLH, Tallahassee is completely frostproof during October. Just as it should be for being the capital of Florida.
https://www.weather.gov/tae/extremes

[Ed's Mountain]

Originally Posted by Can't think of username

I finished those FSU normals! For comparison here are the 2014-2023 normals of KTLH to compare.

Ten-year averages are not normals. They are just ten-year averages.

Originally Posted by Can't think of username

...

Now for how I believe this will help solve the 'inferior' dilemma some users have that this thread is all about.
Just as I was outlining in older comments, it has much warmer lows and seasonal minima in the cool season due to that wet clay soil and cold air drainage. It also has colder average highs, usual monthly maxima, and record highs in every single month because that wet clay is poor for heating up compared to sand - which helps solve the problem of excess heat that is also behind the inferior premise.
In short, the 2 main features behind the inferior premise are reduced notably compared to the airport.

...

Markedly inferior in my opinion. Still has killer freezes despite being far too hot in the summer.

[Can't think of username]

Originally Posted by Ed's Mountain

Ten-year averages are not normals. They are just ten-year averages.

Thanks, I'll amend my statement to the 10-year averages of each. I guess there will be no normals proper for FSU until 2043.

Originally Posted by Ed's Mountain

Markedly inferior in my opinion. Still has killer freezes despite being far too hot in the summer.

You're definitely entitled to this opinion since one member's F- climate is another's A+. Presumably though other members will find it a big step up, since FSU's present averages are very similar to very uncontroversial 1991-2020 New Orleans normals.

I do think it might improve Space_League's opinion if they show up, going by this comment. 5.2C record low in October is one hell of a step up from -1C record low in October (and 2 other Octobers with <5.2C temperatures) within the same 10 year averages.

Originally Posted by Space_League

The forecasted cold snap is a great example of why many posters here are reluctant to consider much of the SEUS to be subtropical. Not that this is normal but it's an example of how unpredictable things can get down here.

[veshyvonny]

Most of it would. I'd say those places in Florida and Texas that get 80F in winter are just tropical though.

[Teegurr]

Originally Posted by veshyvonny

Most of it would. I'd say those places in Florida and Texas that get 80F in winter are just tropical though.

Averages or on occasion? My location hits 80F nearly every winter but it's decidedly subtropical.

[Can't think of username]

Originally Posted by veshyvonny

Most of it would. I'd say those places in Florida and Texas that get 80F in winter are just tropical though.

For an even better example of what Teegurr mentioned, look at Archbold Biological Station! The usual coldest monthly max is 29.6C and it is most definitely not a tropical climate.


But if you meant average highs of 27C+, those places definitely are tropical. Everglades City has 27C+ highs in February and March, and lo and behold it's a tropical savanna climate.

[Can't think of username]

It's also time to do what I mentioned a while back in the Last Frost thread and make some appropriate comparisons with Burlington Pier and FSU Tallahassee now that the new normals are ready. I'm also thinking back to some older conversations on this thread about how Burlington compares to the Southeast US in that regard.

Originally Posted by memph

It was a bit of a freak event yeah, but even if the "freak event" was happening in Toronto, Toronto would not be getting a freeze at a time of year when average daily highs are in the mid 20s, which is like mid-late August here. The earliest Downtown Toronto has ever had a freeze was September 22, all the way back in 1840... In the past two decades, the earliest freeze was October 18 at Downtown Toronto, that's a long way from mid August, in fact average daily highs in that part of October are only 13-14C.

Even somewhere that doesn't get as much lake and UHI moderation, like Hamilton Airport, the earliest freeze (1960-2022 records) was Sept 21, 1991, a date for which the average high is 19.7C.

It actually looks like downtown Toronto and Tallahassee would be pretty close in this respect. The same excess radiational cooling that is eliminated by the elimination of cold hole airport sites also reduces the daytime highs, as mentioned, so that alone helps bridge the gap when the stations are apples to apples.

As was also mentioned, the Tallahassee records were taken outside KTLH before March 29 1961, and before 1940 were taken downtown. The period of record-1939 earliest first frost for downtown Tallahassee is November 10, on which date the period of record-1939 average high is 22.6C.
Meanwhile, downtown Toronto's average September 22 high is 20.7C according to Ed's normals. Less than a 2C difference, and fully apples to apples it might be even less because it's possible those older records were not taken in the vicinity of the 62m high Capitol Hill with the best cold air drainage that is most analogous to downtown Toronto.

Originally Posted by memph

2015
Burlington Pier: Nov 21

2016
Burlington Pier: Nov 20

2017
Burlington Pier: Nov 9

2018
Burlington Pier: Nov 10

2019
Burlington Pier: Nov 7

2020
Burlington Pier: Oct 31

Here's how Burlington Pier compares to FSU Tallahassee in those years.

2015: November 21 vs January 24 first frost, 64 days apart
2016: November 20 vs January 8 first frost, 49 days apart
2017: November 9 vs January 2 first frost, 54 days apart
2018: November 10 vs no frost until January 21 2020, 437 days apart
2019: November 7 vs January 21 first frost, 75 days apart
2020: October 31 vs December 1 first frost, 31 days apart
2021: November 23 vs January 30 first frost, 68 days apart
2022: November 15 vs December 23 first frost, 38 days apart

It looks like in these years, FSU Tallahassee puts Burlington Pier to utter shame, normally outlasting it in the ballpark of 2 months for first frost. Just like it should for being the capital of Florida compared to somewhere in the capital of Ontario.

I've said this before and I'll say so again: I do not live here to watch the all-important Southeast US list get put to shame. Glad to see here rightfully gets put to shame when apples to apples are compared, an appropriate comparison to cold hole Southeast US airports that Burlington can put to shame would be frost hollow Peterborough.
That plays into this older comment too. It would have gotten frost a month before them, which although not in the all-time-record-early ballpark the Southeast US frosts were is much more in line with an apples to apples place.

Originally Posted by memph

Others are might be more sensitive to sudden extreme freezes, especially if they occur while the plants aren't dormant. For example, some plants in the US South may not have been dormant in Oct 18-20 when the first freeze occurred in much of the region, since average daily highs are still around 21-27C at that time of year. Not such a problem in Toronto where average highs at that time of year were only 12-13C and most plants were already hardened off to cooler temperatures and ready for their first freeze.

One final thing to bear in mind is that places like Burlington Pier outlasting cold hole Southeast US airports is often based on 0.1C or similar readings for Burlington etc, and/or exact 0C readings for the US airports. The problem here is that unlike ECCC's precision, weather.gov rounds to single digits, so a 0C at a Southeast US airport could easily be a 0.1C or similar that was just rounded.
Unfortunate, but it does have to be borne in mind.