Midwest winters cooling

[Chinook]

In the last several years, a large part of the central US has experienced colder winters compared to several previous years previous to this.

 

I have picked the 06-07 to 13-14 time period to show that the central US winters have cooled. I also picked the eight winters previous to this (98-99 to 05-06) to show how warm it was relative to the 1950-1995 mean before that. As you can see, the greatest cooling occurred between Iowa and Wyoming.

 

Why has this happened? This is a tough question. I posted the 500mb anomalies for both of these 8-winter periods to see if we can assess the teleconnections. Now of course, teleconnections change significantly within 20-30 day time periods.

 

I think in the 98-99 to 05-06 period, the EPO was more positive, as evidenced by the abnormally low heights in west Alaska, and less arctic air made its way into the Central US. On average, the central US had slightly above normal 500mb heights.

 

in the 06-07 to 13-14 period, the eastern Pacific ridge was stronger, i.e., more negative EPO, and the NAO/AO was more negative. More arctic air made its way into the central US.  I think the persistent "warm blob" of warm water west of Seattle and south of Anchorage had a feedback with the eastern Pacific ridge since about 2012. On average, the central US had slightly below normal 500mb heights.

 

You could probably do a study on how/why several winters were cool in Eurasia recently. Perhaps the arctic air has been traveling to mid-latitude NA/Eurasia more often than average. Then the arctic air may be replaced by warmer-than-average air in the Arctic circle many of the times it travels to mid-latitudes.

 

 

 

 

 

 

[ORH_wxman]

Cohen had a study on the winter colder winters over most of the extra-tropical landmasses in the Northern Hemisphere...the study was back in 2012, and obviously that trend has gotten stronger at least for the central/eastern U.S. with the 2013-2014 and 2014-2015 winters.

 

http://web.mit.edu/jlcohen/www/papers/Cohenetal_GRL2012.pdf

[OKwx2K4]

I believe it is part of a multidecadal cycle. Most likely related to the PDO. According to the graph linked below for my state, it would appear we are entering a cool phase.

http://climate.ok.gov/index.php/climate/climate_trends/temperature_history_annual_statewide/CD00/tavg/Winter

[Drz1111]

I believe it is part of a multidecadal cycle. Most likely related to the PDO. According to the graph linked below for my state, it would appear we are entering a cool phase.

http://climate.ok.gov/index.php/climate/climate_trends/temperature_history_annual_statewide/CD00/tavg/Winter

FWIW, many researchers (including, I believe, Cohen) have interpreted this as a consequence of ACC.  Poles warm more, latitudinal temperature gradient is reduced in the winter, flow becomes more meridional, and places that are generally troughy in the winter (like the central US, which has a semi-permanent trough caused by the Rockies and, to a lesser degree, the Tibetan Plateau) get colder.

[OKwx2K4]

FWIW, many researchers (including, I believe, Cohen) have interpreted this as a consequence of ACC. Poles warm more, latitudinal temperature gradient is reduced in the winter, flow becomes more meridional, and places that are generally troughy in the winter (like the central US, which has a semi-permanent trough caused by the Rockies and, to a lesser degree, the Tibetan Plateau) get colder.

Yeah, I'm aware of that.

[michsnowfreak]

Snowfall has been on the increase for the past 15 years or so in southern MI, but couple that with colder temps of more recent years and winters overall have become noticably more severe. All things considered its like being in a different climate than the one I grew up in (and for a snow lover, thats a good thing). 

[Geos]

Winters have been definitely more snowy and colder as of late in NE IL/SE WI. Growing up in the 90s the winters I remember were not all that bad and not incredible snowy. It's definitely been a different story since the 06-07 winter here. Been averaging 64.5" since that winter! Except for the 2011-12 winter, it's been consistently snowier than normal (43.8").

[michsnowfreak]

Winters have been definitely more snowy and colder as of late in NE IL/SE WI. Growing up in the 90s the winters I remember were not all that bad and not incredible snowy. It's definitely been a different story since the 06-07 winter here. Been averaging 64.5" since that winter! Except for the 2011-12 winter, it's been consistently snowier than normal (43.8").

Agree completely. I too grew up in '90s as well and my memory echos the data. My idea of "deep snow" has changed dramatically.