July 2012: hottest month in U.S. history

By: Dr. Jeff Masters , 7:16 PM GMT on August 10, 2012

During the 1930s, a series of epic heat waves gripped the U.S., drying up the soil in an unprecedented drought that brought about the great Dust Bowl. The most intense heat hit during July 1936, which set a record for hottest month in U.S. history that stood for 76 years. That iconic record has now fallen, bested by 0.2°F during July 2012, which is now the hottest month in U.S. history, said NOAA's National Climatic Data Center (NCDC) this week. So far in 2012, we've had the warmest March on record, 3rd warmest April, 2nd warmest May, and warmest July. These remarkably warm months have helped push temperatures in the contiguous U.S. to the warmest on record for the year-to-date period of January - July, and for the 12-month period August 2011 - July 2012. Twenty-four states were record warm for that 12-month period, and an additional twenty states were top-ten warm. The past fourteen months have featured America's 2nd warmest summer (in 2011), 4th warmest winter, and warmest spring. The summer of 2012 is on pace to be a top-five warmest summer on record, and could beat the summer of 1936 as the warmest summer in U.S. history.


Figure 1. When the temperature peaked at an all-time high of 108° in Minneapolis, Minnesota on July 14, 1936, the want-ad staff at the 'St. Paul Daily News' was provided with 400 pounds of ice and two electric fans to cool the air in the press room. Photo from the Minnesota Historical Society.


Figure 2. Year-to-date temperature, by month, for 2012 (red), compared to the other 117 years on record for the contiguous U.S., with the five ultimately warmest years (orange) and five ultimately coolest years (blue) noted. The 2012 data are still preliminary. The year-to-date period of January - July was the warmest on record by a huge margin--1.0°F. Image credit: NOAA/NCDC.


Figure 3. For the fourth consecutive month, a new U.S. record for hottest 12-month period was set in July 2012. Five of the top-ten warmest 12-month periods in the contiguous U.S. since 1895 have occurred since April 2011. Image credit: NOAA/NCDC.

Most extreme January - July period on record
NOAA's U.S. Climate Extremes Index (CEI), which tracks the percentage area of the contiguous U.S. experiencing top-10% and bottom-10% extremes in temperature, precipitation, and drought, was 46% during the year-to-date January - July period. This is the highest value since CEI record-keeping began in 1910, and more than twice the average value. Remarkably, 83% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically during the first seven months of 2012, and 74% of the U.S. of the U.S. had warm minimum temperatures in the top 10%. The percentage area of the U.S. experiencing top-10% drought conditions was 20%, which was the 16th greatest since 1910. Extremes in 1-day heavy precipitation events were the 24th greatest in the 103-year record.


Figure 4. NOAA's U.S. Climate Extremes Index (CEI) for January - July shows that 2012 has had the most extreme first seven months of the year on record, with 46% of the contiguous U.S. experiencing top-10% extreme weather.

Little change to the U.S. drought during the past week
The great U.S. drought of 2012 remained about the same size and intensity over the past week, said NOAA in their weekly U.S. Drought Monitor report issued Thursday, August 9. The area of the contiguous U.S. covered by drought dropped slightly, from 63% to 62%, and the area covered by severe or greater drought stayed constant at 46%. The area of the country in the worst drought categories (extreme to exceptional drought) doubled from 10 percent last month to 22 percent this month. The extreme dryness and excessive heat devastated crops and livestock from the Great Plains to Midwest. During July, the area of the U.S. covered by moderate or greater drought was 57%, ranking as the 5th largest drought in U.S. history:

1) Jul 1934, 80%
2) Dec 1939, 60%
3) Jul 1954, 60%
4) Dec 1956, 58%
5) Jul 2012, 57%



Video 1. This is Not Cool: Peter Sinclair's July 2012 video from the Yale Forum on Climate Change and the Media couples historical footage with contemporary clips and news segments. In one of the latter, for instance, NBC anchor Brian Williams opens the network’s flagship news program with the words: “It’s now official. We are living in one of the worst droughts of the past 100 years.” NASA scientist James Hansen is featured testifying about risks of “extreme droughts” in the nation’s breadbasket, and I'm featured in a few clips talking about the drought of 2012.

I'll have a new post by noon Saturday.

Wunderground's weather historian Christopher C. Burt has a post looking back at the great Heat Wave of July 1936.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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1695. Patrap
94E Rainbow Loop

Member Since: December 31, 1969 Posts: Comments:
Quoting hurrtracker1994:


Not quite yet. Look at the 850 mb. I am sure we are getting very close though.




ok thanks
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94E looks like it being shear apart
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Quoting Tazmanian:




no close low with 94E?


Not quite yet. Look at the 850 mb. I am sure we are getting very close though.

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Should be classified at 2 p.m. PDT:

Member Since: December 31, 1969 Posts: Comments:
Several here, if not many, were calling for the tropical depression to weaken to a wave days ago. Certainly read several posts yesterday that predicted the demise. Was moving way too fast and had dry air and shear adversely affecting it. Not a big surprise to most of us here. NHC had to do it over, they probably would have left it an invest. During the last 48hrs. TD-07 was probably below 35mph. Koritheman did a blog two days ago predicting just what has happened to TD07.
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1688. hydrus
West Caribbean.
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Quoting hurrtracker1994:


There is still an elongated center. It will need to consolidate a bit first before being classified.




no close low with 94E?
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Quoting wunderkidcayman:

no he is correct he is using the ATCF data and NHC data and if you look most time both data never add up




thats ture
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Quoting MAweatherboy1:
So this is a depression (Gilma)



But this isn't? (94E)



There is still an elongated center. It will need to consolidate a bit first before being classified.
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Quoting Tazmanian:




you need too go look at the nhc site be for you start doing that


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.3N 58.9W
ABOUT 40 MI...65 KM E OF BARBADOS
ABOUT 170 MI...275 KM SE OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.85 INCHES


no he is correct he is using the ATCF data and NHC data and if you look most time both data never add up
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1683. KEEPEROFTHEGATE (Mod)
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So this is a depression (Gilma)



But this isn't? (94E)

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1681. Patrap
Member Since: December 31, 1969 Posts: Comments:
Quoting VR46L:


I dont know Wonderkid there is a lot of dry air in the southern Caribbean it has to combat before it could possibly regenerate


I think it will just give it time and watch it closely
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Quoting aspectre:
11August06amGMT's 13.8n53.1w-13.9n55.1w was re-evaluated&altered
11August12pmGMT's 13.7n53.2w-13.6n55.6w-13.3n57.9w are now the most recent positions
(Vectors and straightline projections have been corrected from the previous mapping)
Derived from (NHC) ATCF data for TropicalDepressionSeven for 11August12pmGMT:
MinimumPressure decreased from 1009millibars to 1008millibars
MaxSusWinds held at 30knots(35mph)56km/h
Vector changed from 267.8°West@26.9mph(43.3km/h) to 262.7°West@26mph(41.8km/h)

POS-Trinidad :: GND-Grenada :: BGI-Barbados :: SLU-St.Lucia :: []-Mustique

The easternmost dot on the connected lines is where 92L-AL07 became TD.7
The easternmost dot on the longest line is TD.7's most recent position

The longest line is a straightline projection through TD.7's 2 most recent positions to its closest approach (within 18miles or 29 kilometres) to a coastline
10August12pmGMT: 10August12pmGMT: TD.7 had been headed for passage over LittleBay,St.Lucy (topBarbados)
10August6pmGMT: TD.7 had been headed for passage over LinnisPoint~Dennery(town) (bottomSLUdumbbell)
11August12amGMT: TD.7 had been headed for passage TD.7 was heading for passage 10.5miles(16.9kilometres)South of St.Lucia
11August6amGMT: TD.7 had been headed for passage 2.8miles(4.4kilometres)North of Barbados
11August12pmGMT: TD.7 was heading for passage over GrantleyAdamsInternationalAirport in ~1hour, then pass over PetiteMustique in ~5&1/2.hours
from now

Copy&paste pos, 10.595n61.023w, bgi, gnd, 12.191n61.602w, slu-13.89n60.883w, ptp, 13.7n50.9w-13.7n53.2w, 13.7n50.9w-13.555n60.942w, 13.708n60.947w-13.555n60.942w, 13.7n53.2w-13.6n55.6w, 13.7n53.2w-13.375n59.616w, 13.335n59.613w-13.375n59.616w, 13.6n55.6w-13.3n57.9w, 13.6n55.6w-13.085n59.462 into the GreatCircleMapper for a larger-scale map and other information
The previous mapping for comparison




you need too go look at the nhc site be for you start doing that


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.3N 58.9W
ABOUT 40 MI...65 KM E OF BARBADOS
ABOUT 170 MI...275 KM SE OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.85 INCHES

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Quoting TropicalAnalystwx13:
Invest 93L still has the potential to develop into a tropical cyclone. It's in cool SSTs and surrounded by a lot of dry air now, but it will enter a favorable environment in about 72 hours, where organization may occur. This is going out to sea though.


I agree, I still think this has a good chance at becoming a hurricane.
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11August06amGMT's 13.8n53.1w-13.9n55.1w was re-evaluated&altered
11August12pmGMT's 13.7n53.2w-13.6n55.6w-13.3n57.9w are now the most recent positions
(Vectors and straightline projections have been corrected from the previous mapping)
Derived from (NHC) ATCF data for TropicalDepressionSeven for 11August12pmGMT:
MinimumPressure decreased from 1009millibars to 1008millibars
MaxSusWinds held at 30knots(35mph)56km/h
Vector changed from 267.8*West@26.9mph(43.3km/h) to 262.7*West@26mph(41.8km/h)

POS-Trinidad :: GND-Grenada :: MQS-Mustique :: BGI-Barbados :: SLU-St.Lucia ::

The nearest dot east of BGI is TD.7's most recent position

The 2 westernmost lines are part of a straightline projection through TD.7's 2 most recent positions to its closest approach (within 18miles or 29 kilometres) to a coastline
10August12pmGMT: TD.7 had been headed for passage over LittleBay,St.Lucy (topBarbados)
10August6pmGMT: TD.7 had been headed for passage over LinnisPoint~Dennery(town) (bottomSLUdumbbell)
11August12amGMT: TD.7 had been headed for passage TD.7 was heading for passage 10.5miles(16.9kilometres)South of St.Lucia
11August6amGMT: TD.7 had been headed for passage 2.8miles(4.4kilometres)North of Barbados
11August12pmGMT: TD.7 was heading for passage over GrantleyAdamsInternationalAirport in ~1hour, then pass over PetiteMustique in ~5&1/2.hours from now

Copy&paste pos, 10.595n61.023w, mqs, bgi, gnd, 12.191n61.602w, slu-13.89n60.883w, ptp, 13.7n50.9w-13.7n53.2w, 13.7n50.9w-13.555n60.942w, 13.708n60.947w-13.555n60.942w, 13.7n53.2w-13.6n55.6w, 13.7n53.2w-13.375n59.616w, 13.335n59.613w-13.375n59.616w, 13.6n55.6w-13.3n57.9w, 13.6n55.6w-13.085n59.462w, 13.6n55.6w-12.834n61.193w into the GreatCircleMapper for a larger-scale map and other information
The previous mapping for comparison
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ok guy I know you want to hear it from me so here it is TD7 has officaly by the NHC and also MY SELF degenerated to a Tropicl Wave

however look out for possible regeneration in the Central Caribbean in a couple of days

I also expect it forward movements to slow down when it reaches the area
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1675. VR46L
Quoting wunderkidcayman:
well advisory is out TD7 is now a tropical wave however they now make it seem that it could regenerate which I think it could and would once it has entered the Central Caribbean

"THE WAVE WILL BE MONITORED FOR SIGNS OF REGENERATION...AND
ADVISORIES WOULD BE RE-INITIATED IF NEEDED."

I think that when it does enter the central caribbean it will be in good enough conditions for quick redvelopment and strengthening so all in the central and western Caribbean keep you eye on Tropical Wave 7/EX-TD 7

models should keep on running through out its "zombie" period


I dont know Wonderkid there is a lot of dry air in the southern Caribbean it has to combat before it could possibly regenerate

Member Since: December 31, 1969 Posts: Comments:
dont say bye bye too TD 7 yet it may come back later
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Quoting SLU:
RECON heading home. Good job guys.



As I was saying earlier the system was almost open when the HH got there and deteriorated rapidly thereafter. They certainly did hunt around a lot at low altitude and gave it the best shot they could.
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1672. hydrus
Here is the other Katrina I remember..Formed November 3, 1981
Dissipated November 8, 1981
Highest winds 1-minute sustained:
85 mph (140 km/h)
Lowest pressure 980 mbar (hPa); 28.94 inHg
Fatalities 2 direct
Areas affected Cuba, Bahamas, Cayman Islands
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1671. Patrap
Gulf Of Mexico - Rainbow Loop
Member Since: December 31, 1969 Posts: Comments:
Invest 93L still has the potential to develop into a tropical cyclone. It's in cool SSTs and surrounded by a lot of dry air now, but it will enter a favorable environment in about 72 hours, where organization may occur. This is going out to sea though.

Member Since: December 31, 1969 Posts: Comments:
also this was a first

"WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR
THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING."
well its either that or they haven't been thanking them in recent times so might as well do it now

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ULL over the NW Caribbean may be an interesting feature to watch today. Looked like a little surface spin was trying to form yesterday just south of Western Cuba. Not saying a LLC is going to form but I think the area will blob up again and one may try to form. Disturbed area of weather just east of Florida may get interesting too.
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1667. SLU
RECON heading home. Good job guys.

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What's next down the pipe line?
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Well, goodnight all. stay well, stay safe.
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1664. VR46L
Bye bye TD7



even in rainbow

Member Since: December 31, 1969 Posts: Comments:
well advisory is out TD7 is now a tropical wave however they now make it seem that it could regenerate which I think it could and would once it has entered the Central Caribbean

"THE WAVE WILL BE MONITORED FOR SIGNS OF REGENERATION...AND
ADVISORIES WOULD BE RE-INITIATED IF NEEDED."

I think that when it does enter the central caribbean it will be in good enough conditions for quick redvelopment and strengthening so all in the central and western Caribbean keep you eye on Tropical Wave 7/EX-TD 7

models should keep on running through out its "zombie" period
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Quoting AussieStorm:
SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.3N 58.9W
ABOUT 40 MI...65 KM E OF BARBADOS
ABOUT 170 MI...275 KM SE OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.85 INCHES

I'm guessing this is the main reason why TD-07 is now an open wave. it's hauling a big time.


Yes that, a little wind shear, and some dry air all contributed.
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Quoting Tribucanes:
TD7 officially going to be reclassified as an open wave soon? Was beautiful as a wave about a week ago, many here commented that it was a great looking invest. Been sad and piddly since and not getting any healthier. Wonder if the NHC is second guessing ever upgrading it to TD7?



TD 7 is dead in the water right now
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1660. msphar
Geat news! Dead on the doorstep! I will sleep well tonight.
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Quoting hurrtracker1994:


Oh wow called it. lol


mmmm a lot of us have been calling it for the last 12hrs.
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1658. Skyepony (Mod)


TRMM 3B42 Rain Rates (shaded) overlaid with 200 hPa Velocity Potential Anomalies (contoured)
Negative 200 hPa Velocity Potential Anomalies (Divergence) are cool-colored contours
Positive 200 hPa Velocity Potential Anomalies (Convergence) are warm-colored contours
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1657. SLU
Excerpt:

WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR
THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING.


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1656. SLU
Excerpt:

WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR
THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING.


Member Since: Posts: Comments:
SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.3N 58.9W
ABOUT 40 MI...65 KM E OF BARBADOS
ABOUT 170 MI...275 KM SE OF MARTINIQUE
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.85 INCHES

I'm guessing this is the main reason why TD-07 is now an open wave. it's hauling a big time.
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Quoting hurrtracker1994:
Good morning everyone! To me it looks as though TD7 has degenerated into an open wave. HH haven't really found a center, and 850 mb vorticity shows an elongated structure which is indicative of an open wave and the LLC falling apart.



Oh wow called it. lol
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WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING.

Love how Dr. Avila slips in the human touch to so many of his discussions over the years.........
Member Since: December 31, 1969 Posts: Comments:
1652. sar2401
Quoting sar2401:


It has a slight chance of reaching TS category before it dies, but I doubt it. I asked several days ago if a TD has ever been reclassified back to an invest (other than the obvious error we had on 07), so it might be interesting


Never mind! It's now officially "Remnants of TD7". I guess that rules out an invest.
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1936and 1934 had warmer high temperatures, but 2012 had warmer minimum temp (thanks to in large part by UHI)

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000
WTNT42 KNHC 111438
TCDAT2

REMNANTS OF SEVEN DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL AL072012
1100 AM AST SAT AUG 11 2012

AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE DEPRESSION
HAS OBSERVED SHARP WIND SHIFTS AT AN ALTITUDE OF 1000 FT...BUT IT
HAS BEEN UNABLE TO LOCATE A PERSISTENT AND WELL-DEFINED CENTER OF
CIRCULATION. THE DEPRESSION HAS THEREFORE DEGENERATED INTO A
TROPICAL WAVE...AND ADVISORIES ARE BEING DISCONTINUED AT THIS TIME.
THE WAVE WILL BE MONITORED FOR SIGNS OF REGENERATION...AND
ADVISORIES WOULD BE RE-INITIATED IF NEEDED.

THE WAVE CONTINUES TO MOVE RAPIDLY TO THE WEST AT AN ESTIMATED SPEED
OF 22 KT. THE AXIS OF THE WAVE SHOULD MOVE ACROSS THE LESSER
ANTILLES THIS EVENING AND THEN CONTINUE WESTWARD ACROSS THE
CARIBBEAN SEA DURING THE NEXT FEW DAYS. HEAVY RAINS AND WIND GUSTS
TO TROPICAL STORM FORCE ARE STILL POSSIBLE ACROSS PORTIONS OF THE
LESSER ANTILLES LATER TODAY AND TONIGHT.

WE WOULD LIKE TO THANK THE AIR FORCE RESERVE HURRICANE HUNTERS FOR
THEIR HARD WORK INVESTIGATING THE SYSTEM THIS MORNING.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 13.3N 58.9W 30 KT 35 MPH
12H 12/0000Z...DISSIPATED

$$
FORECASTER BERG/AVILA
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Lightning Strike Digs Trench

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1648. SLU
Quoting SLU:
...TROPICAL DEPRESSION DEGENERATES INTO A TROPICAL WAVE...SQUALLY WEATHER STILL LIKELY ACROSS PORTIONS OF THE LESSER ANTILLES LATER TODAY AND TONIGHT...


Can't say I disagree with that.
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1647. sar2401
Quoting Tribucanes:
TD7 officially going to be reclassified as an open wave soon? Was beautiful as a wave about a week ago, many here commented that it was a great looking invest. Been sad and piddly since and not getting any healthier. Wonder if the NHC is second guessing ever upgrading it to TD7?


It has a slight chance of reaching TS category before it dies, but I doubt it. I asked several days ago if a TD has ever been reclassified back to an invest (other than the obvious error we had on 07), so it might be interesting
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1646. SLU
...TROPICAL DEPRESSION DEGENERATES INTO A TROPICAL WAVE...SQUALLY WEATHER STILL LIKELY ACROSS PORTIONS OF THE LESSER ANTILLES LATER TODAY AND TONIGHT...
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Good morning everyone! To me it looks as though TD7 has degenerated into an open wave. HH haven't really found a center, and 850 mb vorticity shows an elongated structure which is indicative of an open wave and the LLC falling apart.

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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather