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Late August Heat Wave


Chicago Storm
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Temp went from 77 to 78 at ORD... at 3 am central time.
A tidbit about Wed night/Thu morning for Chicago.  Since records began, there have only been 6 occurrences of 80 degree lows in August and none after 8/21.  Will #7 happen and make it the latest day in the year with a low of 80?  Stay tuned.

Low of 78 at ORD.


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2 hours ago, Chicago Storm said:


Low of 78 at ORD.


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Ties the daily record high min, set in 2018 (!).  Also, there has never been a min of 79+ after today's date.  Normal low at ORD is 61, although that's also been a joke the past 5-10 summers, as ORD seems to have above-average mins in summer on 75%+ of days.  It's like grade inflation; "every day is above average".

I know it's beating a dead horse, but the UHI at ORD is crazy and just keeps getting worse.  RFD, not exactly a rural paradise, had a low of 72 this morning.  Same air mass, yet 6 degrees cooler than ORD.  FEP hit 70.  There was no easterly component to the wind, so the warm lake had nothing to do with it.

UHIs are so unfortunate anywhere they occur, as it's indisputable evidence that humans are messing with nature.

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43 minutes ago, beavis1729 said:

Ties the daily record high min, set in 2018 (!).  Also, there has never been a min of 79+ after today's date.  Normal low at ORD is 61, although that's also been a joke the past 5-10 summers, as ORD seems to have above-average mins in summer on 75%+ of days.  It's like grade inflation; "every day is above average".

I know it's beating a dead horse, but the UHI at ORD is crazy and just keeps getting worse.  RFD, not exactly a rural paradise, had a low of 72 this morning.  Same air mass, yet 6 degrees cooler than ORD.  FEP hit 70.  There was no easterly component to the wind, so the warm lake had nothing to do with it.

UHIs are so unfortunate anywhere they occur, as it's indisputable evidence that humans are messing with nature.

I agree about UHI

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1 hour ago, Hoosier said:

Today might be warmer than yesterday at ORD. :sun:

Half joking

I agree that it has been surprising how high the DPs have been around here during this heat wave, even with the very dry ground.  That has made it challenging to predict the high temps each day.  The dew never dropped below 61, and was 65-70 most of the time.  Maybe it's because the air is advecting over wetter ground/corn fields...or that late August is generally a climatologically humid time of year, especially if the air isn't coming directly out of Canada?

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the UHI at ORD is crazy and just keeps getting worse.  RFD, not exactly a rural paradise, had a low of 72 this morning.  Same air mass, yet 6 degrees cooler than ORD. 

No doubt it’s UHI and RFD is conveniently located to help genuinely to compare and contrast.

That said, RFD proper is 5% the size of Chicago proper in terms of population (150k vs 2.7m). Assuming land area is somewhat linear then it really isn’t much of a comparison.

This is a foolish, non science based comparison - putting that aside - with these figures you could say that for every 400k in population concentrated in an “area” the average temperature of that area will rise by 1 degree Fahrenheit, if building / land use is comparable (eg I would compare a million population third world city to a million population developed city as the amount of concrete will be wildly different). With that, RFD with its 150k population only raises temp by 1/3 of a degree F.
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50 minutes ago, luckyweather said:


No doubt it’s UHI and RFD is conveniently located to help genuinely to compare and contrast.

That said, RFD proper is 5% the size of Chicago proper in terms of population (150k vs 2.7m). Assuming land area is somewhat linear then it really isn’t much of a comparison.

This is a foolish, non science based comparison - putting that aside - with these figures you could say that for every 400k in population concentrated in an “area” the average temperature of that area will rise by 1 degree Fahrenheit, if building / land use is comparable (eg I would compare a million population third world city to a million population developed city as the amount of concrete will be wildly different). With that, RFD with its 150k population only raises temp by 1/3 of a degree F.

Yep, understood.  Of course there is no "one size fits all" rule, and it depends on the season and the antecedent conditions on a given day.  But, anecdotally, I'd suggest the average UHI impact is a bit greater than what you noted. 

This morning, RFD (72F) was 2F warmer than "baseline"...namely FEP, a very small nearby rural town that dropped to 70F.  Overall, from what I've seen over the years, RFD will check in at 1-2F warmer than nearby rural areas.  Probably 2-3F higher at night (especially in winter), and 0.5-2F higher during the day.  Just estimates, of course...but significantly greater than 1/3 of a degree F.

Another example - the MSP metro area (3.5 million population) has a huge UHI problem...amplified further in the winter when the rural vs. urban differences in radiational cooling become apparent.  I've seen many winter mornings were it will be -10F to -15F in areas outside (and even south of) the metro area, but MSP will be much warmer, around 0F.

And, sometimes, it can come down to the very microscale detail of the exact location of the ob site.  You always hear about the joke of DCA (one of the Washington DC airports), where the thermometer is right on the tarmac and right by the river.  DCA also records much lower snowfall totals due to this.  Same idea with BDL - Bridgeport CT. I know airports have historically been a convenient place to record wx obs, but it's probably not the most representative when jet exhaust and concrete can be even more intense than a "regular" urban area.    

Not meaning to argue about this, of course...just a good discussion. :)

Back to the heat wave - looks like ORD hit 94/70/100 today.  While I'm on a roll with pet peeves, it's still shocking to me how there have been no heat advisories in the Chicago metro area all week, when we've had 5 (?) consecutive 90+ days...especially noting that it's late August and can be considered "out of season" heat.  I would even suggest there should've been heat advisories if this were June/July...but especially for late August.  A heat index of 95+ is pretty miserable, especially with full sun, the cumulative effects day after day, and little nighttime relief in the metro/urban core (heck, ORD had a low of 78 this AM...and it was probably similar in Chicago proper with 2.8 million people).  But I digress... 

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On 8/22/2020 at 12:16 PM, Hoosier said:

Suppose I will take a crack at highs for ORD.

Who cares about today/tomorrow.  Let's get to the good stuff.

 

Mon:  93 (actual:  97)

Tue:  97 (actual:  91)

Wed:  99 (actual:  94)

Thu:  96 (actual:  95)

 

Wednesday is the only day I see that has a realistic shot at hitting 100.  Tuesday would be about as likely as making a halfcourt shot while blindfolded.

 

Well, this was not a very good performance overall, with the exception of today which was only a 1 degree miss at 5 days lead time.  Was too cool on 1 day and too warm on 3 days.  Tuesday was affected by that outflow situation which I had not factored in at the time, but I am skeptical that it would have made it into the upper 90s even without that.  Better luck next time.

I am starting to think that the only way to get to 100 is if a regional drought sets in early enough to take out a sig amount of the crops upstream.  8 years and counting for Chicago.

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9 hours ago, hawkeye_wx said:

Last day of the heat wave, thankfully.  You don't realize how important a backyard/patio shade tree is until it's gone.

If you have enough room plant an Autumn Blaze Maple back there.  Fantastic tree, and extremely fast growing.  

Made it to 94 at MLI, and 93 here today.  25 days AOA 90 at MLI for the year, and 24 here.

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