The Northeast Heatwave

By: Dr. Jeff Masters , 9:08 AM GMT on July 07, 2010

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Hi, Dr. Rob Carver, filling in for Jeff while he's on vacation.

The most significant weather event in the US on July 6, 2010 didn't show up on any radar. The geostationary satellites didn't see it in their constant watch over the Earth's atmosphere. Instead, the tale of this event was told by the thermometers, because the heatwave in the Northeast was the most significant event for July 6, and it will likely be the most important weather story for July 7.

The heat wave covers Pennsylvania to Maine, but Tuesday's worst was centered over New York City. All six of the stations used by the New York NWS office for climate reports (Central Park, La Guardia, JFK, Islip, Bridgeport, and Newark) set or tied the daily high temperature record. Newark and Central Park both reached 103 degrees F.

How unusual is this heat wave?
Figures 1 and 2 show how warm the highs and lows are compared to 30 year averages. Unless you were at the Great Lakes, the Midwest and Northeast have highs well above normal, with 10-15+ degree F differences over the coastal cities of the Northeast. Using my gridded temperature data, the low for New York City was 6 degrees F above normal, which should happen 30% of the time (1.1 standard deviations away from normal). The high was roughly 20 degrees above normal, which should happen only 0.29% of the time (3.04 standard deviations away from normal). This is an unusually strong heat wave.

Why it's hot
Basically, it's because there is "the Bull of a high pressure ridge [over the NE US]" to quote the Mount Holly NWS office forecast discussion. The large ridge of high pressure is forcing air to slowly descend across the Northeast, preventing clouds from forming. Without no clouds and plenty of daylight, the Sun heats the ground which then heats the air.

When will it cool down?
That's an excellent question. A trough of low pressure off the coast will bring onshore winds to the Tri-State area and MA by Thursday, so they should cool down a bit. The southern part of the heat wave, DC and Philadelphia, will have to wait for a cold front to arrive from the Great Lakes sometime Saturday to get relief.

Population affected
As Figure 3 shows, heat advisories covered most of the urban areas of the northeastern US. By my calculations, over 32 million people were under a heat advisory. Different offices have different guidelines for heat advisories. The NWS office responsible for New York issues a heat advisory if the heat index will be above 95 deg. F for two or more days or if the index will be above 100 deg. F for any length of time.


Fig.1 Plot of the difference between maximum temperature (the high for the day) and average maximum temperature in degrees F for July 6.


Fig.2 Plot of the difference between minimum temperature (the low for the day) and average minimum temperature in degrees F for July 6.


Fig.3 Plot of the active heat advisories across the northeastern US for July 6.

Heatwave impacts
The predominant impact from heat waves is increased mortality. CDC estimates that over 8,000 people died during heat waves from 1979 to 2003. That's more than all of the deaths due to lightning, flooding, tornadoes, hurricanes, and earthquakes. The elderly, sick, poor, and very young face the worst of the effects of the heat. Wikipedia has an interesting article describing the Chicago Heat Wave of 1995, a modern heat wave with a large number of fatalities due to the heat.

Heatwave coping strategies
The Centers for Disease Control have some tips for dealing with the heat. In summary, drink plenty of water, spend time in air-conditioned buildings, and wear light-colored clothing.

Is this heat wave due to global warming?
Ah, the $64,000 question. In the absence of detailed analysis, it's hard to specify the exact cause for this heat wave, from a meteorological or climatological view point. However, events like this are consistent with research showing that heat waves are more likely with
global warming
. I like the metaphor of loaded dice, global warming is not specifically responsible for any heat wave, but it will make them happen more often.

Tropics
My thinking on Invest 96L is unchanged from this blog entry. In summary, I believe that 96L has a <50 % chance becoming a tropical cyclone before it makes landfall. If it does so, it will likely be near the coast when that happens. In any event though, the winds and waves it generates will likely disrupt oil spill recovery efforts. Also, I would expect a broad area of showers and 20+ mph winds will affect the Gulf coast somewhere from south Texas to Louisiana.

Next update
I'll have an update this afternoon to talk about the tropics.

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1337. oakland
Quoting TropicalAnalystwx13:
I say that the 8 PM percentage for 96L will be between 0 and 100%


LOL You can't possibly be wrong.
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I say that the 8 PM percentage for 96L will be between 0 and 100%
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Quoting StSimonsIslandGAGuy:
And I think the heatwave header is entirely appropriate, since the 1980 heatwave killed over 1,000 people in the USA, and another heatwave killed over 700 in Chicago in 1995. 96L has no chance of a death toll like that.


Heat wave?? ... its hotter than that everyday here in SE Texas from May - Sept and it never makes national news..

Its summer time so it does happen to get hot!! You'll never see the triple digits here reported on the E coast ever... makes zero sense...
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1334. Levi32
Quoting TexasHurricane:


Hi Levi, any changes in your thinking on 96L?


Nope, no changes from my blog entry earlier this afternoon.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting Levi32:


Depends on how you define "center". All invests are given coordinates but they do not necessarily represent a low pressure center of any kind or the center of any kind of circulation. In disorganized disturbances the "center" is given as just the approximate center-point of the area of disturbed weather.
It was sorta meant in a sarcastic way, like the center point of a system, not necessarily the circulation.
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I would say yes to code red.
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Quoting Levi32:


Depends on how you define "center". All invests are given coordinates but they do not necessarily represent a low pressure center of any kind or the center of any kind of circulation. In disorganized disturbances the "center" is given as just the approximate center-point of the area of disturbed weather.


Hi Levi, any changes in your thinking on 96L?
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Quoting hunkerdown:
60.1%
LOL. Ok, that's it.
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Quoting bakers:


Oh really?





If that doesn't have a center, then neither does the Houston Rockets. ;)


Member Since: September 7, 2007 Posts: 1 Comments: 937
1327. Levi32
Quoting MiamiHurricanes09:
All systems have a center.


Depends on how you define "center". All invests are given coordinates but they do not necessarily represent a low pressure center of any kind or the center of any kind of circulation. In disorganized disturbances the "center" is given as just the approximate center-point of the area of disturbed weather.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
1326. Dakster
Are we getting a red alert for the 8pm??
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Quoting MiamiHurricanes09:
LOL! Ok I'll take your prediction. But that's it.
60.1%
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I think a 60 percent.... or maybe 50 but all these people saying 70 and 80..... i think is an overstatement
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Quoting KarenRei:


It comes right before the THREE. ;)

(j/k -- Tropical Weather Outlook)


But isnt it also found after the one??? or even between the 1 and the 3??

LOL
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Quoting hunkerdown:
does that mean I miss out on the chance for a cookie ? Probably was stale and out of date anyway :)
LOL! Ok I'll take your prediction. But that's it.
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A TD a 8:00
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Quoting bakers:
All systems have a center.
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1318. Patrap
96L has now and to the Coast to make a run on Lowering the Central Pressure and becoming all she can be.

That H to the NE is gonna scoot things along.

W to WnW.

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Quoting earthlydragonfly:
Evening everyone...

ok it is driving me crazy now.... What is the "TWO" everyone is talking about? I assume short for something...


Tropical Weather Outlook. The product the NHC releases four times per day, once every six hours. It can be found here (just look below the image of the Atlantic, and it will say "Tropical Weather Outlook").
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Quoting Levi32:


Tropical Weather Outlook....from the NHC.


AAAAAaaaahhhhhhh.... Thanks Levi
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Quoting earthlydragonfly:
Evening everyone...

ok it is driving me crazy now.... What is the "TWO" everyone is talking about? I assume short for something...


It comes right before the THREE. ;)

(j/k -- Tropical Weather Outlook)
Member Since: September 7, 2007 Posts: 1 Comments: 937
Quoting KarenRei:
Stron

Yep. Nothing more than a big ball of warm-core convection with a surface circulation over tropical waters in low to moderate shear with increasingly sustained convection over its center and an anticyclone overhead. Who ever heard of something like that developing?

;)


Yep. Never heard of it.
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Quoting MiamiHurricanes09:
Polls are now closed and no more predictions will be received.
does that mean I miss out on the chance for a cookie ? Probably was stale and out of date anyway :)
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1312. bakers
Quoting KarenRei:
if it had a center it would be classified and it is not going to be.
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1311. Levi32
Quoting earthlydragonfly:
Evening everyone...

ok it is driving me crazy now.... What is the "TWO" everyone is talking about? I assume short for something...


Tropical Weather Outlook....from the NHC.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Polls are now closed and no more predictions will be received.
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1309. USSINS
Imminently landfalling tropical system/depression (maybe more) and we've a heatwave header still. Yup, lots of heatwave posts today. ;)

Seems to more accurately reflect AGW politics rather than the nature of severe weather itself.

Yup, it's hot alright, but there's at least substantial, serious dangerous, life-threatening flooding coming to a large portion of the western GoM. Thanks out to the tropical posters here, staying abreast of the current conditions and possibilities.

Let's hope 96L doesn't it get its act together.
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Evening everyone...

ok it is driving me crazy now.... What is the "TWO" everyone is talking about? I assume short for something...
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Quoting KarenRei:
Stron

Yep. Nothing more than a big ball of warm-core convection with a surface circulation over tropical waters in low to moderate shear with increasingly sustained convection over its center and an anticyclone overhead. Who ever heard of something like that developing?

;)
C-L-A-S-S-I-C
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1303. Levi32
I say 60% from the NHC...it should be a "high" chance in any case.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting MiamiHurricanes09:
Last call!

What percentage will the NHC give 96L of tropical cyclone formation in the next 48 hours on the 8PM TWO?

The person that guesses correctly gets a cookie. Lol.

By the way I went with a 70% chance.


I'll play, I'll say 80% just to be different.
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Stron
Quoting bakers:
96L will not develope. it is nothing more than a big ball of convection.


Yep. Nothing more than a big ball of warm-core convection with a surface circulation over tropical waters in low to moderate shear with increasingly sustained convection over its center and an anticyclone overhead. Who ever heard of something like that developing?

;)
Member Since: September 7, 2007 Posts: 1 Comments: 937
Quoting TxMarc71:
Heavy topical rain here in Houston for the last couple hours..

almost no thunder and lightning.. very little wind .. just flat out heavy tropical rain


Really? Pearland here I have heard plenty of thunder..including now...but not while the rain is pouring...weird.
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1298. Drakoen
I say the NHC gives it a 70% chance
Member Since: October 28, 2006 Posts: 57 Comments: 29886
1297. Jynni99
I say 65% they have been conservative lately...IMO
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Quoting MiamiHurricanes09:
Last call!

What percentage will the NHC give 96L of tropical cyclone formation in the next 48 hours on the 8PM TWO?

The person that guesses correctly gets a cookie. Lol.

By the way I went with a 70% chance.


70%.
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1294. bakers
96L will not develope. it is nothing more than a big ball of convection.
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Quoting Drakoen:
Nicely developed low pressure system is 96L.

Very impressive on satellite.
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Last call!

What percentage will the NHC give 96L of tropical cyclone formation in the next 48 hours on the 8PM TWO?

The person that guesses correctly gets a cookie. Lol.

By the way I went with a 70% chance.

Everything will close at 7:30 PM EDT.
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Quoting Hardcoreweather2010:
Looks less organized than it was a couple of hours ago and not nearly the man that 95L was. I expect 96L to go poof overnight but the effects will still be the same for Texas and MX.


Then it is fair to state that you believe it will stay orange or go down to yellow at 8:00 p.m.?
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1290. Drakoen
Nicely developed low pressure system is 96L.

Member Since: October 28, 2006 Posts: 57 Comments: 29886
1289. Patrap
Click FRONTS and MSLP

Gulf Of Mexico - Water Vapor Loop
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Quoting reedzone:
Over the past few hours, it seems that the structure is starting to improve fast.. Got my crow defrosting for tomorrow.


LMAO. Takes a real man to eat crow! Impressive.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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