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

[Can't think of username]

Originally Posted by memph

Southern Ontario gets seasonal lag but I guess early April/mid November would be better comparisons in terms of vulnerability to extreme cold. At that point the average low is above freezing, you can expect freezes once or twice a week but they're typically light, anything below -5C would be possible but rare.

Downtown Toronto has something like a 0.2% likelihood of -10C temperatures on any given mid-November or early April day, which would translate to -10C temperatures being a once a decade event in Dallas winters if the winter days in Dallas have a comparable likelihood of -10C temperatures. Even in the last two weeks of March, only about 1/10 days drop below -5C and 1/100 to 1/50 drop to -10C based on the last 3 decades of records.

I would stick with Oshawa to compare with Dallas as it keeps the consistency between a quintessential humid continental climate and a quintessential subtropical climate.

Unlike Oshawa, downtown Toronto makes the Dfa margin by a bit, whereas the quintessential humid continental climate would be a Dfb within a degree or two C of being Dfa. There seems to be a bit smaller transition from hot summer continental to subtropical than from warm summer continental to subarctic, so one would need to account for this with a humid continental climate a bit towards Dfb.

A slight Dfa would need a slightly warmer end subtropical climate like New Orleans. The coldest temperature of the year there between the various airport, Audubon, and Lakefront stations averages to about -2C, which would be much more in line with what Downtown Toronto would be getting in April and/or October (maybe average the 2 out?).

I will say though that your guess is right on the money. -10C has only happed at Love Field 3 times in 1991-2020, so exactly 0.2% chance.

Originally Posted by memph

This is only a comparison of vulnerability to harsh cold though, Dallas will still get a lot more warmth on an average winter day than Toronto would in Mid-Nov/early Apr.

Yep, Dallas gets a lot more warmth than either (particularly Oshawa).

For what it's worth though, conversely Dallas gets a median of 9 days (29% of days) below freezing in January for 1991-2020. I wonder how this stacks up to April and October in Oshawa, presumably it is comparable based on what I have experienced in those months in Oshawa.

[Can't think of username]

Originally Posted by memph

That's probably right actually. Delhi did have a few times when the diurnal range was 18-20C which I guess were the rare times it had clear skies day & night for rapid warming & cooling.

Ex Oct 4-5 and Oct 23-24.
https://www.timeanddate.com/weather/...h=10&year=2022

However, Waterloo Airport's clay dominated soils seem to have experienced equally large diurnal variations on those clear days/nights.

So we have
-UHI effects
-water body moderation
-soil moisture
-soil type
-cloud cover
-daylength/sun angle

All as possible factors impacting diurnal range.

I would be curious at which point the evapotranspiration at Bush Field drops to significant enough degree that the soil is moist. Here in the sandy Lake Ontario waterfront, the soil is moist from about mid-late October to early-mid April. This year I actually even had to water my leafy greens with the warm late Oct/early Nov weather.

Usually temperatures of 15-20C are enough to cause the sandy soil here to dry out after a few days without rain.

I think it doesn't drop enough, the rainy season is summer but of course that's going to be directly counteracted by higher temperatures summer brings. That's why even July in Augusta is no July at like St. Simons Island

[memph]

Originally Posted by Can't think of username

I think it doesn't drop enough, the rainy season is summer but of course that's going to be directly counteracted by higher temperatures summer brings. That's why even July in Augusta is no July at like St. Simons Island

Oh for sure summer is going to have periods of dry soil, especially at the upper 2-5cm. My assumption was that the best chance for long term wet soil would be in the winter, when rainfall is still significant (90-100mm is still more than we get in fall) and evapotranspiration rates are much higher. The "transpi" part can be pretty important by the way - with the peppers I'm overwintering in my basement, the ones that are dormant have pots where the soils stays moist for months without watering while the ones that have full foliage and are ripening fruit need about 1-2L of water (for 2-3 gal pots) per week. If they were outside in the summer they might need 3-4L per week. And in a cool 10C greenhouse in the fall, maybe only 0.5-1L per week.

That means the pepper plants are pumping something like 70mm/month of rain equivalent out of the soil and into the air at 18C room temperature in the basement (it would probably be less in humid outdoor air but still).

[Can't think of username]

We've got ourselves a pattern change on the 13th-15th which I think showcases very nicely the variations in cool season weather the Southeast US gets.
Obviously some users have a real problem with it but I think it's extra fun for my weather monitoring. I've said this before in this thread and can't say it enough now that it's ongoing.

Albany Georgia is one of the best examples of this fun. Today it has a hot 26C high but will get a bit cold with this pattern change, 3 frosts are forecast for the January 13-15 window as low as -3C.
As a matter of fact, since January 13 is tomorrow, it will be going from hot to cold in a day. Such fun variety to see when it doesn't interfere with frost monitoring!

For reference it has a January average of 9.1C, making it not only a middle ground subtropical climate but also very similar to my April/October weather in a quintessential humid continental climate. And those extremes are exactly what I experience in those months, making monitoring the weather all the more fun and relatable.

I can see why some people would have a problem with 26C to 0C-3C in 1-4 days, but I can't ever see myself being among them.

[Space_League]

pattern change is playing out in real time here. Heavy storms rolling in and tornado watch for Atlanta metro



spoiler it just keeps dropping after 11pm and keeps dropping until 9am tomorrow, stays where it lands all day (5-7c) then drops again tomorrow night to around freezing.

Next week will still be warm again though. This January has basically been like March normally is for, both in the temps and the storm activity

[Can't think of username]

Originally Posted by Space_League

pattern change is playing out in real time here. Heavy storms rolling in and tornado watch for Atlanta metro



spoiler it just keeps dropping after 11pm and keeps dropping until 9am tomorrow, stays where it lands all day (5-7c) then drops again tomorrow night to around freezing.

Really not all that bad tbh. This reminds me of the January 22 2020 cold front JUST like I suspected it would, South Florida will be very close to its normal seasonal minimums but North Florida northwards will be let off comparatively very easy.
Areas as far north as Cape Hatteras are forecast for no frost, and if Atlanta had the South Florida forecasts you would be forecast for perhaps -7C to -8C at your house/Bobby Dodd and -9C at Hartsfield-Jackson.

Originally Posted by Space_League

Next week will still be warm again though. This January has basically been like March normally is for, both in the temps and the storm activity

You're right, both on the big warmup next week and March-January. Atlanta has been nearly identical to March so far.

I can't say this enough either: going to have to keep a close eye on the March or later backloading from warm December-February that ruins last frost tracking, unless this is a highly desirable 2020 repeat where the backload didn't come until May and my list was safe. 2017, 2018, and 2022 all taught me that the hard way.

[Can't think of username]

Originally Posted by Can't think of username

If I had to guess I think January will be good for both of them. They were quite above normal in the January 1990 analogue, probably because the Christmas outbreaks of both 1989 and 2022 used up cold air that otherwise would have come.

Halfway point of the month and lo and behold I ended up right on the money so far! Some aspects of this are quite similar to December.

Charleston Int'l is currently at 13.6C for January, 3.9C above normal. Monthly extremes so far are 26C/-2C.
Downtown Charleston is currently at 13.3 for January, 2.9C above normal. Monthly extremes so far are 22C/1C.

Dallas Love Field is running 5.3C above normal at 14.1C compared to the normal of 8.8C. Monthly extremes so far are 28C/1C.
Dallas Arts District is probably running a similar amount above normal, or possibly slightly more since it seems to have benefitted from radiational cooling given its extremes. Monthly extremes so far are 28.4C/4.5C(!)

What's quite similar to December is, as Space League pointed out with that fabulous summary, Dallas beats Charleston out where it's completely unexpected to do so.
Contrary to what you would expect, not even Love Field has recorded any frosts while Charleston Int'l has gotten a hard frost - in fact Love Field ties for the minimum with downtown Charleston(!) and the Arts District blows even downtown Charleston out of the water (pun intended) by a full 3.5C.

Looks like in this case the Appalachian protection didn't do squat for Charleston. It's more common than one would expect for that to be the case, March 2017 and 2018 are 2 back to back great examples.
Can't wait to see whether the whole month ends up like this, it would be fun if it keeps going this way with no backload.

As a matter of fact, like I said in the last frost thread, Dallas Love Field might stand a chance of breaking the all time earliest last frost record set on January 8 2017. It just needs to be as lucky as it was from today-onward in 2017.
And that's lovely compensation for getting left in the dust for 33 days by Charleston Int'l in the first frost contest.

[hunters1212]

It is rather continental, but still less so than similar latitudes in east Asia. So no, it's quite nice even in most of the winter. In the Deep south. The bit of cold weather can be nice. I really enjoy some cold, and wish we had a bit more

[GraniteStater]

Originally Posted by hunters1212

It is rather continental, but still less so than similar latitudes in east Asia. So no, it's quite nice even in most of the winter. In the Deep south. The bit of cold weather can be nice. I really enjoy some cold, and wish we had a bit more

Most of the US is much too far south in latitude for the cold to have staying power in the winter. You have to be at least 43N latitude to have four well defined seasons with more substantial changes in daylight between summer and winter.

[Space_League]

Originally Posted by GraniteStater

Most of the US is much too far south in latitude for the cold to have staying power in the winter. You have to be at least 43N latitude to have four well defined seasons with more substantial changes in daylight between summer and winter.

Chicago has pretty well defined four seasons