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It Really Was a Heat Wave II (unless it wasn't, in which case it was weak sauce)- - Obs and Disco Late June/Early July 2012

HoarfrostHubb

By HoarfrostHubb,
in New England

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HoarfrostHubb

HoarfrostHubb

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I'm not sure the high dews can hang around as long as they say...EEN already has dropped to a 46F dew. ORE down to 60F. BAF down to 62F...we'll see how the 7pm obs go. Dew will climb again in the radiational cooling spots overnight, but that will also cause the actual temp to drop quite a bit.

How does that happen? Why do the dews go up? Thermodynamics is not my specialty

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ORH_wxman

ORH_wxman

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The air feels nice this evening. Perfect summer's eve.

Good night for some Summer Shandy ad the Two Towers

Pretty sweet dewpoint drop for you sarting shortly before 7pm...showing up nicely on the meso station near you.

23krs3n.jpg

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Ginx snewx

Ginx snewx

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BTV just posted this on their Facebook Page...impressive!

"It's a hot day across Northern New York and Vermont today, but we aren't the only ones! As of 4PM, 26 states have at least one reporting station with temperatures of 100 degrees or higher, and all but 3 states in the lower 48 (Maine, Washington, and Oregon) have temperatures 90 degrees and above."

RI?

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Logan11

Logan11

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It wasn't bad here today. 84.5 was the warmest as the cooler air blew in on nw winds. Atrocious in the HV where they got downsloped and it was low/mid 90's.

Yeah pretty cool watching that track across the region. We dropped quickly and then have since rebounded a bit back up to a Td of 56F. I think its also getting to be that time of day where they'll rise a bit here as we start to decouple when the sun goes behind the mountains.

However, you can see the real core of dry air in the southern portions of BTV's forecast area... Rutland and Springfield are both in the 40s for dews, same with SW New Hampshire.

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ORH_wxman

ORH_wxman

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How does that happen? Why do the dews go up? Thermodynamics is not my specialty

The dewpoint rises in the evening in raditional cooling spots because as the air cools rapidly without advecting dry air into it, you start to saturate it since warm air holds a lot more actual moisture than cool air. So you start to get a wetbulbing effect where the temp drops and the dewpoint rises.

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ORH_wxman

ORH_wxman

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No I was questioning wether RI hit 90 as it stated only 3 states.....

I can't find an ASOS station that hit 90F in RI...so maybe they got it wrong unless they are using weenie mesonet sites. But I"m not sure even any of those hit 90F.

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powderfreak

powderfreak

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I can't find an ASOS station that hit 90F in RI...so maybe they got it wrong unless they are using weenie mesonet sites. But I"m not sure even any of those hit 90F.

They were likely using the mesonet stations... BTV uses a lot of MADIS and the various mesonetworks from what I can tell. That's what their daily climate maps and things like that are based on... its only logical to use mesonets when there's only like 3-6 ASOS stations per NWS office.

However, who knows if they even came up with that or if it was some stat that the NWS headquarters or PR department or another NWS office came up with.

26 states with 100F or higher is pretty darn impressive. Plus, RI is really just a part of CT anyway ;) (cue Ginx)

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dendrite

dendrite

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The dewpoint rises in the evening in raditional cooling spots because as the air cools rapidly without advecting dry air into it, you start to saturate it since warm air holds a lot more actual moisture than cool air. So you start to get a wetbulbing effect where the temp drops and the dewpoint rises.

That same radiational cooling lowers your mixing heights which probably allows plant respiration (or any remaining transpiration) to add a little moisture at the sfc too since you cut off your ability to mix lower dews down.

Kevin probably notices this too on his Davis when a turbulent 10mph eddy mixes the 80F dewpoint out of his radiation shield above his watered lawn.

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scoob40

scoob40

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72/49, High DP's all night long? what is Kevin on? Just perfect here. I thought "torches" were supposed to be uncomfortable. Pfffft.

Goshen was 87/70 today and the Stump was 88.1/70. Very comfortable conditions by any standards. Even Peru at 1900' was 83/67. 2k must have been an oasis today right ?

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ORH_wxman

ORH_wxman

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That same radiational cooling lowers your mixing heights which probably allows plant respiration (or any remaining transpiration) to add a little moisture at the sfc too since you cut off your ability to mix lower dews down.

Kevin probably notices this too on his Davis when a turbulent 10mph eddy mixes the 80F dewpoint out of his radiation shield above his watered lawn.

I think we know the real reason now Kevin tries to keep a lawn on steroids...keep those dewpoints up in the summer.

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Diego

Diego

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The dewpoint rises in the evening in raditional cooling spots because as the air cools rapidly without advecting dry air into it, you start to saturate it since warm air holds a lot more actual moisture than cool air. So you start to get a wetbulbing effect where the temp drops and the dewpoint rises.

Will, I defer to you as the expert here, but intuitively, I would think that a rise in dewpoint with a correspondingly temperature drop without advection would mean an increase in absolute humidity levels. If I'm correct, where is this additional moisture coming from without advection? You referred to this as a wetbulbing effect. Can you explain this thermodynamically?

BDL dewpoint 52 now and ORH 50F...so boundary through there.

I note that at 8pm, Hartford, not Bradley, still had a dp of 69, and Pougkeepsie, 70. So it looks like the drier air will not reach the NYC metro area or coastal SNE.

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dendrite

dendrite

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I think we know the real reason now Kevin tries to keep a lawn on steroids...keep those dewpoints up in the summer.

I've been enjoying his microscale dewpoint updates though. The dewpoint over my parents' hot tub got up to 85F today...impressive.
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ORH_wxman

ORH_wxman

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Will, I defer to you as the expert here, but intuitively, I would think that a rise in dewpoint with a correspondingly temperature drop without advection would mean an increase in absolute humidity levels. If I'm correct, where is this additional moisture coming from without advection? You referred to this as a wetbulbing effect. Can you explain this thermodynamically?

The dewpoint starts rising when you get condensation on the laminar layers of the surrounding environment. Your air mass has a certain amount of moisture in it...when you lose the heat to radiational cooling, you do not lose any moisture with it for the most part, so it can only eventually condense and cause evaporational cooling which causes wetbulbing and an associated dewpoint rise since as the air cools, it can no longer hold the moisture.

There's a lot of micro-processes that go on in the environement during radiational cooling, so I'm trying to speak in as easy layman's terms as possible. I probably cannot even explain some of the weirder stuff that happens that contributes...such as what dendrite mentioned, the lowered mixing heights hold in more moisture too.

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ski MRG

ski MRG

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Goshen was 87/70 today and the Stump was 88.1/70. Very comfortable conditions by any standards. Even Peru at 1900' was 83/67. 2k must have been an oasis today right ?

Had a high of 86.4 here, 2k had a high of 82 when I left. As Wxmanmitch noted the west wind was blowing all day. Mid 80's around the 4th of July, what's the big deal? seems like quintessential summer weather to me. Certainly nothing life threatening or extreme. As much as some want to characterize this weather as some sort of intense heat episode it just isn't. The real teeth of the heat will stay far far away from here. It's the folks in the mid section of the nation that can crow about extreme heat. New england has no claim on that prize. This Summer has the feeling of one that just never quite delivers a knockout punch. It's like a Winter that never quite gels. You can sense it. The Unremarkable Summer of 2012. I couldn't ask for more. I'll look forward to watching the Olympics late this month as yet another trough sets up over us. Fantastic.

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