Severe winter weather in parts of the US

[Summer Sun]

Polar Vortex To Plunge US Temperatures to -60C

 

Windchills of nearly -60C (-70F) are threatening to turn states in the north and northwest US into an icy deep freeze. A phenomena described as a polar vortex is set to suck super-chilled air from the Arctic into North and South Dakota, the Great Lakes states and New England, sending temperatures plunging. Washington DC has already seen its coldest temperatures for 20 years and several Mid Western states have recorded their lowest mercury readings for more than a decade. Weather Bell meteorologist Ryan Maue described current weather conditions as a once in a generation event. "If you're under 40 (years old), you've not seen this stuff before," he said. But with much of the north east of the country already under thick snow and well below zero, a newly emerging weather system is threatening to cause further misery.

 

The 'polar vortex' is an anti-clockwise rotating pool of cold, dense air that forms close to the North Pole, but typically hangs over Canada. Meteorologists say that unusually, this year, it is heading south and moving towards the north and eastern United States. Fargo in North Dakota is expected to dip to -31C (-25F), International Falls, Minnesota will fall to -35C (-31F) and Indianapolis, Indiana and Chicago, Illinois, will reach -26C (-15F).

 

Meanwhile, in Brazil, soaring temperatures in Rio de Janeiro set off fire sprinklers in shopping malls as the thermometer topped 40C (102F). Thousands headed to the beach as temperatures rose to more than 50C in the sunshine.

 

http://news.sky.com/story/1190455/polar-vortex-to-plunge-us-temperatures-to-60c

[Summer Sun]

US cold plunge continues

 

Some parts of North America could see their lowest temperatures in years over coming days. Matt Taylor has more.

 

http://www.bbc.co.uk/weather/feeds/25605106

[mike Meehan]

Never mind, perhaps it will be our turn 2014/15

[SLEETY]

crazy cold,maybe our turn soon

[Summer Sun]

Polar Vortex: 187 Million Hit By Big Freeze

 

http://news.sky.com/story/1191336/polar-vortex-187-million-hit-by-big-freeze

[Summer Sun]

All 50 US states, including usually balmy Florida, see sub-zero temperatures as the record-breaking cold spell spreads.

[Beverley Lass]

Hi all,

I wondered if Niagara Falls might freeze and I see it is

doing so ..

 

http://www.mirror.co.uk/news/world-news/pictures-niagara-falls-frozen-polar-3003781

[Richard Lake]

Probably late in posting this one, but here is a recent video from the USA in the last few days.

https://m.facebook.com/story.php?story_fbid=10203136384594199&id=1344562217&_rdr

Very unusual. Discuss.

[Vorticity0123]

It seems like the western part of the United States has seen a major change in weather during the past few days! 5 days ago, the maximum temperature recorded was below -10*C. Yesterday, the maximum temperature almost hit 16*C, which is a difference of 26*C in just 5 days! The historical temperature data of New York can be seen in the link below:

 

http://www.wunderground.com/cgi-bin/histGraphAll?day=12&year=2014&month=1&ID=KNYC&type=1&width=614

 

Moreover, the 16*C almost broke the daily maximum record for the 12th of January (16.3*C)¹

 

Synoptics change

 

The reason for the drastic change in weather was a change in the overall weather pattern. For an analysis, look at the GFS chart of 8th of January below:

GFS 8 January 500 hPa geopotential heights and surface pressure

 

The white contour lines are the surface isobars, the black contours lines are the lines of equal geopotential at 500 hPa. The colors on the map also indicate geopotentials, but then corrected for topographical influences (correct me if I'm wrong on the last)

 

What can be seen is a very distinct surface low pressure area (as well as at 500 hPa) over Northeastern Canada. Moreover, there is a surge of very low geopotentials (purple colors) flowing toward New York from the east. The low pressure area was very well stacked from the surface all the way to 100 hPa (that is where the connection to the polar vortex lies, will be discussed later). 

 

The low pressure area sent an area of very low 850 hPa temperatures from the pole toward New York (as the low pressure was in place for quite some time by then), resulting in the severe cold, as shown below:

 

GFS 8 January 850 hPa temperatures

 

The 850 hPa temperatures at New York were around -20*C around that time.

 

4 days later, the situation was quite different. Take a look at the GFS 500 hPa chart for 12 January:

GFS 12 January 500 hPa geopotential heights and surface pressure

 

A marked trough (noted in surface as well as in 500 hPa, it can be seen with the low geopotential heights dipping southward) can be seen extending all the way down to the Gulf of Mexico. The very low geopotential heights associated with the polar vortex moved nortwesttward away from Northeastern Canada. As a result of the trough to the (south)east of New York, the flow turned to the south, sending very warm air from the Gulf of Mexico toward the city. This can also be seen at the 850 hPa temperature charts:

 

GFS 12 January 850 hPa temperatures

 

Note the pool of very warm 850 hPa temperatures extending from the Gulf of Mexico toward the southeastern tip of Canada. New York had 850 hPa temperatures of about 10*C at that time, which is a 30*C increase in about 4 days.

 

Stratospheric connection

 

As the low pressure area the 8th of January was so well stacked, it was also visible at 100 hPa, as the polar vortex. This can be seen below:

ECMWF stratosphere (100 hPa) geopotential heights of 8 January.

 

Note the main center of the polar vortex was being located over Northeastern Canada, almost exactly where the low surface and (more important) 500 hPa heights were. This means the polar vortex was (in)directly connected to the cold in many parts of the US.

 

Now take a look at the 100 hPa heights on the 12th of January:

ECMWF stratosphere (100 hPa) geopotential heights of 12 January.

 

The main lobe of the polar vortex has moved northwestward away from the east of the US. Still, the polar vortex hasn't moved that much, compared to 4 days ago. This indicates that the situation of a polar vortex being perfectly alligned with low surface heights at the bottom is not a very common situation. Therefore, 100 hPa heights shouldn't be used as a direct indicator wheather cold is coming or not.

 

Concluding, it has been an impressive temperature swing in the west of the US. It is a nice example of how quickly the weather can change from the one extreme to the another. It will be interesting to see how the weather will develop in the western part of the US during the next week or so. For now, it seems like a return to normal temperatures will be the most likely, finally.

Sources:

http://www.wunderground.com/history/airport/KNYC/2014/1/12/MonthlyHistory.html#calendar

http://www.weather.com/weather/wxclimatology/daily/USNY0996 ¹

http://www.wetter3.de/Archiv/ (for the GFS charts)

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/winterdiagnostics/

http://www.weeronline.nl/Noord-Amerika/Verenigde-Staten/New-York/3931993 (for the future weather prediction)

Edited January 12, 2014 by Vorticity0123

[keithlucky]

Extreme cold to hit the midwest and east USA again as USA met man  said Wow f------g wow

Edited January 21, 2014 by keithlucky

[keithlucky]

And its stuck there for at least ten days.

[picog]

And its stuck there for at least ten days.

That might be ominous for the UK if it's cold and snow you're after.