Extreme Drought to Flood in Georgia: Weather Whiplash Strikes Again

By: Dr. Jeff Masters , 3:57 PM GMT on May 06, 2013

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The remarkable storm that brought record-breaking May snows and cold to the Midwest last week continues to spin over the Southeast U.S. The storm is unleashing flooding rains, bringing a case of "Weather Whiplash" to Georgia: flooding where extreme drought had existed just a few months ago. The storm formed when a loop in the jet stream of extreme amplitude got cut off from the main flow of the jet over the weekend, forming a "cutoff low" that is now slowly spinning down as it drifts east over the Southeast U.S. On Sunday, the storm dumped 3.4" of rain on Atlanta, Georgia--that city's sixth heaviest May calendar day rain storm since record keeping began in 1878. Remarkably, the rains were also able to bring rivers in Central Georgia above flood stage. This portion of the country was in "exceptional drought"--the worst category of drought--at the beginning of 2013.


Figure 1. The record May snowstorm that hit the Midwest U.S. on May 1 - 3, 2013, got cut off from the jet stream and was seen spinning over the Southeast U.S. on Sunday, May 5, in this image from NASA's MODIS instrument. The 3.4" of rain that fell on Atlanta, Georgia on May 5 was that city's sixth heaviest May calendar day rainfall since record keeping began in 1878.

Weather Whiplash
Weather Whiplash--a term originally coined by science writer Andrew Freedman of climatecentral.org to describe extreme shifts between cold and hot weather--is also a excellent phrase we can use to describe some of the rapid transitions between extreme drought and floods seen in recent years. I brought up a remarkable example in mid-April, when a 200-mile stretch of the Mississippi River north of St. Louis reached damaging major flood levels less than four months after near-record low water levels restricted barge traffic, forcing the Army Corp to blast out rocks from the river bottom to enable navigation. As the climate warms, the new normal in coming decades is going to be more and more extreme "Weather Whiplash" drought-flood cycles like we have seen in the Midwest and in Georgia this year. A warmer atmosphere is capable of bringing heavier downpours, since warmer air can hold more water vapor. But you still need a low pressure system to come along and wring that moisture out of the air to get rain. When natural fluctuations in jet stream patterns take storms away from a region, creating a drought, the extra water vapor in the air won't do you any good. There will be no mechanism to lift the moisture, condense it, and generate drought-busting rains. The drought that ensues will be more intense, since temperatures will be hotter and the soil will dry out more.


Figure 2. Weather Whiplash in Georgia, 2013: the center of the state was in exceptional drought as the beginning of the year, but heavy rains in February, March, and April busted the drought. Heavy May rains have now brought flooding. Image credit: U.S. Drought Monitor.

Weather Whiplash in the Southeast U.S. more likely due to an intensification of the Bermuda High
This year's "Weather Whiplash" in Georgia is the second time in the past decade the state has gone from exceptional drought to flood. In September 2007, Atlanta, Georgia was in the midst of a 1-in-100 year drought, and was just weeks away from running out of water. Yet just two years later, the drought had been busted, and a phenomenal 1-in-500 year flood ripped through the city, killing ten and causing $500 million in damage. According to a 2011 study by a Duke University-led team of climate scientists, "Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States", the frequency of abnormally wet or dry summer weather in the southeastern United States has more than doubled in recent decades, due to an intensification of the Bermuda High. The scientists found that the Bermuda High, which is centered several hundred miles to the east of the Southeast U.S., has grown more intense during summer and has expanded westwards over the past 30 years. Since high pressure systems are areas of sinking air that discourage precipitation, this has made abnormally dry summers more common over the Southeast U.S. However, in summers when the Bermuda High happens to shift to the east, so that high pressure is not over the Southeast U.S., the stronger winds blowing clockwise around the Bermuda High bring an increased flow of very moist subtropical air from the south to the Southeast U.S., increasing the incidence of abnormally wet summers. Thus, the intensification of the Bermuda High has made extreme droughts and extreme floods more likely over the Southeast U.S. Using climate models, the scientists determined that human-caused global warming was likely the main cause of the significant intensification in the Bermuda High. Thus "Weather Whiplash" between drought and flood will probably become increasingly common in the coming decades over the Southeast U.S.


Figure 3. Observed June-July-August departure of precipitation from average over the SE United States for a 60-yr period (mm day−1). Horizontal dashed lines represent 1 standard deviation of the summer rainfall. Note that summer precipitation extremes exceeding one standard deviation have more than doubled during the most recent 30-year period compared to the previous 30-year period. Image credit: Li et al., 2011, Journal of Climate.

New climate change blog at The Guardian
In these days of steadily decreasing media coverage of climate change (and all science, in general), its good to see a fresh new source of good science appear in a major newspaper. The Guardian, a prominent UK news source, has a new blog called Climate Consensus – The 97%. The primary authors are Dana Nuccitelli of SkepticalScience and John Abraham, Associate Professor at the University of St. Thomas in Minnesota. The first post at the new blog is titled “Why is Reuters puzzled by global warming’s acceleration?”

Related Links
Don't miss the summary post on last week's remarkable snow storm by wunderground's weather historian, Christopher C. Burt, The Phenomenal May Snowstorm of May 1-3, 2013

Extreme Drought to Extreme Flood: Weather Whiplash Hits the Midwest: my April 19, 2013 blog post.

Southeast U.S. drought: another Tropical Storm Alberto needed: my April 2012 post describing how 20% - 50% of all droughts in the Southeast U.S. are broken by tropical storms or hurricanes.

Study: Global warming is driving increased frequency of extreme wet or dry summer weather in southeast, so droughts and deluges are likely to get worse: October 2010 post by Joe Romm at climateprogress.org.

Jeff Masters

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Quoting MississippiWx:


We've had something to watch in the Western Caribbean in late May/early June the past 3 years. I have been watching with interest the long range GFS which has been hinting at tropical stirrings in this area of the world around that time. It will be something to keep an eye on for sure.


The 12-15 day GFS has had "something" in the western Caribbean literally almost every run for the last 3 weeks. It is next to useless in the early season because it has a bias of allowing the monsoonal circulation to invade the Caribbean.

If it shows a robust cyclone that leaves the Caribbean Sea, then that might be a clue to the future, but "rumblings in the deep" at the end of the GFS run almost never mean anything this time of year.

All of that said, ever since the twin Indian TCs were forecasted back in late April, I've been saying it could set up the EPAC / Caribbean in late May or early June, so I think we will have to watch that region soon enough.
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CPC 5/6/13 update=Nino 3.4 at 0.0C
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Quoting Gearsts:
Funny because i live in the wettest part of the islands but the pattern for rain has been different from last couple of years for the start of may.


Yeah your afternoon thunderstorms are getting pulled NE toward San Juan.
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Just some random storm pictures I took between Mid-April to yesterday:







This one is looking straight up to a 45,000 foot storm. Looks are deceiving!

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Skew-T of one of those clusters in Africa.



Its a wave alright.
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Quoting StormTrackerScott:


Western side of the island has been left high and dry.
Funny because i live in the wettest part of the islands but the pattern for rain has been different from last couple of years for the start of may.
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Quoting SouthernIllinois:

It's called Climate Change now.
That would be incorrect. Global warming is one facet--or symptom, if you will--of climate change. The two terms are not interchangeable by scientists, nor have they ever been; while some may be confused about the terminology, climatologists certainly aren't.

I'm very pleased to see that the Guardian is filling in where other outlets, swayed by perhaps by a lazy desire to provide "balance" where none truly exists, have become lax in their journalistic duties. Kudos to them for providing an invaluable service...
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Quoting Gearsts:
Not a single drop here since May 1.


Western side of the island has been left high and dry.
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Quoting Gearsts:
Not a single drop here since May 1.


Yeah I have some friends in PR that are praying for some rain as it has been dry for the last 6 months.
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Quoting sunlinepr:
Seems like a billion gallons of rain over us.... just a typical month of may...



Rainy season kicking into high gear for u guys.
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Quoting sunlinepr:
Seems like a billion gallons of rain over us.... just a typical month of may...

Not a single drop here since May 1.
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Quoting Grothar:
Quoting Grothar:


Lots of those tracks criss cross Orlando.
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Seems like a billion gallons of rain over us.... just a typical month of may...

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Quoting LargoFl:


An occluded front. Havent seen one of those in a while.
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Member Since: August 6, 2011 Posts: 4 Comments: 37084


Link
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A Degree of Difference


So, the Earth's average temperature has increased about 1 degree Fahrenheit during the 20th century. What's the big deal?

One degree may sound like a small amount, but it's an unusual event in our planet's recent history. Earth's climate record, preserved in tree rings, ice cores, and coral reefs, shows that the global average temperature is stable over long periods of time. Furthermore, small changes in temperature correspond to enormous changes in the environment.

For example, at the end of the last ice age, when the Northeast United States was covered by more than 3,000 feet of ice, average temperatures were only 5 to 9 degrees cooler than today.
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Even though it's still a week out, it looks like I'll be getting my first significant dose of warm weather starting early next week:

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Quoting FLGatorCaneNut:


Started Today !!!


It actually appears to be retrograding today.

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Quoting Grothar:


They are not speaking of a direct strike, but of estimated times a hurricane coming within 50 miles of a given area based upon historical estimates.



Todays globes? :D
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Quoting Jedkins01:


The hurricane return period for the Tampa Bay area and northeast Florida/South Georgia should be in the 25 to 50 year color coding.

That just doesn't seem right, there is absolutely no way the hurricane return period here around Tampa Bay is shorter than western Louisiana and is supposedly the same as the western Florida panhandle/Alabama/Miss coastline...


They are not speaking of a direct strike, but of estimated times a hurricane coming within 50 nautical miles of a given area based upon historical estimates.
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Quoting hurricanes2018:



That image is what i look at every day, really useful :D
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FLOOD ADVISORY
NATIONAL WEATHER SERVICE RALEIGH NC
209 PM EDT MON MAY 6 2013

NCC063-183-061930-
/O.NEW.KRAH.FA.Y.0009.130506T1809Z-130506T1930Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000 Z.OO/
DURHAM NC-WAKE NC-
209 PM EDT MON MAY 6 2013

THE NATIONAL WEATHER SERVICE IN RALEIGH HAS ISSUED AN

* URBAN AND SMALL STREAM FLOOD ADVISORY FOR HEAVY RAINFALL AND MINOR
FLOODING IN...
DURHAM COUNTY IN CENTRAL NORTH CAROLINA...
WAKE COUNTY IN CENTRAL NORTH CAROLINA...

* UNTIL 330 PM EDT

* AT 206 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS WITH HEAVY RAINFALL OVER WAKE AND DURHAM COUNTIES.
DOPPLER RADAR ESTIMATED A HALF INCH TO AN INCH OF RAIN HAS FALLEN
SINCE 100 PM. ADDITIONAL RAINFALL AMOUNTS OF UP TO AN INCH WILL BE
POSSIBLE THROUGH 300 PM.

* RUNOFF FROM THIS HEAVY RAINFALL WILL CAUSE MINOR FLOODING TO
OCCUR...ESPECIALLY ALONG SMALL STREAMS...IN LOW LYING AREAS...AND
AREAS OF POOR DRAINAGE. SOME LOCATIONS THAT WILL EXPERIENCE MINOR
FLOODING INCLUDE...CARY...DURHAM...RALEIGH...FUQUAY-VARINA. ..
GARNER...RDU INTERNATIONAL...ROUGEMONT AND WAKE FOREST.
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Quoting SouthernIllinois:

It's called Climate Change now.


Yep. The climate is always changing. Global temps go up and down. Right now they are going up. In the future they will go down.
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BBC weather video: Floods hit France
6 May 2013 Last updated at 17:01

The weather guy is mentioning a healthy tornado in Northern Italy in the evening of May 3rd. It might have already been mentioned here; sorry then for posting it again:



Maybe the US has exported their usual tornados to Europe this season? ;-)

Another youtube video of this event.
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Enjoy this low while you still can, because it is begining to lose its form, and I predict it to look like a sloppy mess as it weakens overnight.
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137. VR46L
Quoting FLGatorCaneNut:


Started Today !!!


just a little but its gonna take its sweet time to get out of that area...





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Quoting VR46L:
This swirl has hardly moved in days..







Started Today !!!
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Quoting MississippiWx:


We've had something to watch in the Western Caribbean in late May/early June the past 3 years. I have been watching with interest the long range GFS which has been hinting at tropical stirrings in this area of the world around that time. It will be something to keep an eye on for sure.

quite right mate
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Quoting StormTrackerScott:
MJO increases across the Caribbean come late May.





We've had something to watch in the Western Caribbean in late May/early June the past 3 years. I have been watching with interest the long range GFS which has been hinting at tropical stirrings in this area of the world around that time. It will be something to keep an eye on for sure.
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Quoting wunderkidcayman:


this also contributes to why the Western Caribbean generally gets the most storms than anywhere else in the Atlantic Basin Western Caribbean this mainly includes Cayman Islands Cuba Honduras and Jamaica

also area like S Florida Yucatan and Bahamas thought these are more like secondary targets for most storms
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Quoting MississippiWx:


You can? Hmmm. Interesting. :-)


Stupid work computer. It's a little jumpy today:)
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Quoting StormTrackerScott:


In May it is common for an area of low pressure to get drawn north off Panama or South America into the SW Caribbean. That is why the western Caribbean can be active at times in Late May.


this also contributes to why the Western Caribbean generally gets the most storms than anywhere else in the Atlantic Basin Western Caribbean this mainly includes Cayman Islands Cuba Honduras and Jamaica
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Quoting nrtiwlnvragn:


Tampa area would include storms striking the East Coast of Florida and exiting on the West Coast.


Interesting as to the reasoning why the return period is higher in Western and Central LA...I guess it is the way the synoptic patterns usually set up with the semi-permanent pressure systems
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Quoting Gearsts:
Can the MJO cause warming in the El nino regions as it moves east?


Yes because of the warm westerlies it brings with it.
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Quoting StormTrackerScott:


I can at times.


You can? Hmmm. Interesting. :-)
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Quoting Gearsts:
Can the MJO cause warming in the El nino regions as it moves east?


It can at times.
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Quoting StormTrackerScott:
MJO increases across the Caribbean come late May.



Can the MJO cause warming in the El nino regions as it moves east?
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MJO increases across the Caribbean come late May.



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At first it was blaming human caused global warming because the globe was warming. Now we're blaming human caused global warming on extreme cold, warmth, drought, floods etc.... So I guess we can blame human caused global warming on just about every weather event that happens. Temps are below normal here in Florida today. I blame global warming.
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Quoting Gearsts:
Isn't that area of low pressure always there?


In May it is common for an area of low pressure to get drawn north off Panama or South America into the SW Caribbean. That is why the western Caribbean can be active at times in Late May.
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Quoting Gearsts:
Isn't that area of low pressure always there?


Monsoon trough
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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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