Jeff Masters on Jet Stream Extremes, and Obama’s Climate Plan

July 4, 2013

Above, Weather Channel Interview with Jeff Masters on Obama’s groundbreaking climate address.

Below, commentary on jet stream patterns of the last month.

Jeff Master’s Wunderground blog:

The jet steam is exhibiting unusual behavior over the U.S., a pattern we’ve seen become increasingly common in summertime over the past decade. There’s a sharp trough of low pressure over the Central U.S., and equally sharp ridges of high pressure over the Western U.S. and East Coast. Since the jet acts as the boundary between cool, Canadian air to the north and warm, subtropical air to the south, this means that hot extremes are penetrating unusually far to the north under the ridges of high pressure, and cold extremes are extending unusually far to the south under the trough of low pressure. The ridge over the Western U.S., though slowly weakening, is still exceptionally intense.

This ridge, which on Sunday brought Earth its highest temperatures in a century (129°F or 54°C in Death Valley, California), was responsible for more record-breaking heat on Tuesday. July 2. Most notably, Redding, California hit 116°, just 2° short of their all-time record. Death Valley had a low of 104°, the second hottest night on record since 1920 (the hottest was just last summer!) Numerous daily high temperature records were set in Arizona, California, Nevada, Utah, Montana, Oregon, and Washington. It was the opposite story in the Central U.S., where the southwards-plunging jet stream allowed record cold air to invade Texas. Waco, Texas, hit 58°F this morning (July 3), the coldest temperature ever measured in July in the city. Numerous airports in Texas, Nebraska, Arkansas, Louisiana, Kansas, and Missouri set new daily record low temperatures this morning. And over the Eastern U.S., the northward-pointing branch of the jet stream is creating a potentially dangerous flooding situation, by pulling a moisture-laden flow of tropical air from the Gulf of Mexico over the Florida Panhandle north-northeastward into the Appalachians. Up to five inches of rain is expected over this region over the next few days, and wunderground’s severe weather map is showing flash flood warnings for locations in Florida, Georgia, South Carolina, and North Carolina.

Figure 1. Jet stream winds in the upper atmosphere at a pressure level of 300 mb on July 3, 2013. The jet had an unusually extreme configuration for summer, with a sharp trough of low pressure over the Central U.S., and equally sharp ridges of high pressure over the Western U.S. and East Coast. Image from the wunderground jet stream page.

Third extreme jet stream pattern of the past five weeks
This week’s extreme jet stream pattern is the third time in the past five weeks that we’ve seen a highly amplified ridge-trough pattern that has led to extreme weather. The others:

1) The end of May and beginning of June, when the $22 billion Central European floods occurred. A high pressure ridge became stuck over northern Scandanavia, causing all-time May heat records–as high as 87°F–at stations north of the Arctic Circle in Finland. The high pressure ridge blocked low pressure systems from moving north, and a series of two low pressure systems dumped record rains over Austria and Germany, creating the highest floods ever seen on portions of the Danube River. The $22 billion price tag made it the 5th most expensive non-U.S. weather-related disaster in world history.

2) June 18 – 22, when a ridge of high pressure over Alaska broke all-time heat records in the state, with unofficial readings as high as 98°F. A low pressure system became trapped over Alberta, Canada, bringing the city of Calgary a$3 billion flood disaster. This was the most expensive flood in Canadian history, and third most expensive natural disaster of any kind for the country. The only more expensive disasters were a 1989 wildfire ($4.2 billion) and a 1977 drought ($3 billion.)

As I discussed in a March 2013 post, “Are atmospheric flow patterns favorable for summer extreme weather increasing?”, research published this year by scientists at the Potsdam Institute for Climate Impact Research (PIK) in German found that extreme summertime jet stream patterns had become twice as common during 2001 – 2012 compared to the previous 22 years. One of these extreme patterns occurred in August 2002, during Central Europe’s previous 1-in-100 to 1-in-500 year flood. When the jet stream goes into one of these extreme configurations, it freezes in its tracks for weeks, resulting in an extended period of extreme heat or flooding, depending upon where the high-amplitude part of the jet stream lies. The scientists found that because human-caused global warming is causing the Arctic to heat up more than twice as rapidly as the rest of the planet, a unique resonance pattern capable of causing this behavior was resulting. According to an email I received from German climate scientist Stefan Rahmstorf, one of the co-authors of the study, unusually extreme jet stream amplitudes likely played a role in the May – June Central European flooding event.

8 Responses to “Jeff Masters on Jet Stream Extremes, and Obama’s Climate Plan”


  1. […] Jeff Masters on Jet Stream Extremes, and Obama's Climate Plan … […]


  2. […] Above, Weather Channel Interview with Jeff Masters on Obama's groundbreaking climate address. Below, commentary on jet stream patterns of the last month. Jeff Master's Wunderground blog: The jet st…  […]


  3. […] (h/t Michigan native and guy behind Climate Denier Crock of the Week Peter Sinclair.) […]


  4. “… research published this year by scientists at the Potsdam Institute for Climate Impact Research (PIK) in German found that extreme summertime jet stream patterns had become twice as common during 2001 – 2012 compared to the previous 22 years.”

    I had written an email to Dr. Jennifer Francis.

    In it I posted the main thesis:

    „The claim that the melting – a changing Arctic ice extent – mainly responsible for the change in the jet stream, is based on a very low degree of correlation (virtually none – not statistically significant) between the both parameters.”

    “Significant changes in the jet stream occurred after 2008 and are strongly correlated with extremely low solar minimum and the current very weak solar cycle 24. In addition, at that time strongly indicated the negative phase of the PDO, AMO entered a positive phase, there were essential – the natural changes in the index and the oscillation of Arctic, oscillations associated with the Arctic.”

    I received this reply:

    “You are correct that sea ice loss alone is not enough to affect the jet stream appreciably. We link jet stream changes to Arctic amplification, which is caused by a number of factors. Sea ice loss is only one of those factors that affects mainly fall and winter, and mainly the lowest layers of the atmosphere. Earlier loss of the snow cover on high-latitude land contributes to Arctic amplification during late spring and summer, while increasing water vapor content warms upper layers of the atmosphere in all seasons. Other studies have also found that the atmospheric response to sea ice loss alone has not yet been statistically significant as well, but recent analyses of model simulations for the future when ice loss is more dramatic do show a robust response.

    Our work also suggests that the same types of extreme conditions will not be experienced year after year in the same location, only that the jet stream will assume a more amplified trajectory. Other atmospheric features likely dictate where ridges and troughs will set up, such as the natural fluctuations of ENSO, PDO, AO, etc.”

    I will fill it with these observations and conclusions:

    Rigor (2002, http://seaice.apl.washington.edu/AO/ ): “Here it is shown that the memory of the wintertime AO persists through most of the subsequent year: spring and autumn SAT and summertime sea-ice concentration are all strongly correlated with the AO-index for the previous winter.”

    Or maybe memories some positive of winter AO phase (occurring several consecutive years – 1990 to 1996 – a phenomenon never seen before – enhanced resonance) lasts longer?
    (http://www.arctic.noaa.gov/detect/detection-images/climate-ao_nov-mar_2011-600.png)

    Other oscillations:

    Swingedouw (2010. http://www.springerlink.com/content/g589501544320529/):
    “Changes in wind stress, notably due to the NAO, modify the barotropic streamfunction in the Atlantic 50 years after solar variations. [XIX solar cycle: we have extremely – very high solar activity, probably not recorded for at least seven thousand. years …].”

    Matei (2012., http://www.mpimet.mpg.de/nc/en/news/single-news/article/multi-year-prediction-of-the-atlantic-meridional-overturning-circulation-at-265-n-possible.html):
    „Multi-year prediction of the Atlantic Meridional Overturning Circulation at 26.5°N.”
    “The results of the study demonstrate that the skill of climate prediction arises not only from the large ocean thermal inertia, but also from the LONG TIMESCALES of internal ocean dynamics.”


  5. OK, Arctic ice is in transition. The Jet Stream is in transition. Our weather is in transition.

    Does anyone have any idea what will happen when the Arctic and the Jet Stream settle down into a stable pattern for the next thousand years, and what this will mean as far as the advanced forecast rainfall maps that have already been published?

    I would sort of like to have a good idea where the family might want to resettle.


  6. […] our recent experience argues for caution. The kind of caution that should encourage us to support President Obama’s foray – at long last – into the climate policy debate. And this caution must lead to action to curb […]


  7. […] 2013/07/04: PSinclair: Jeff Masters on Jet Stream Extremes, and Obama’s Climate Plan […]


  8. […] 2013/07/04: PSinclair: Jeff Masters on Jet Stream Extremes, and Obama’s Climate Plan […]


Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: