8/14/2019 Arctic Cold and Louisville

1/1

Pacific

Ocean

CANADA

MEXICO

Air pressure and winds around the Arctic that switch between two phases help determine weather in Januarythrough March. The current pattern has brought colder than normal weather for much of the country.

Atlanticsto

r

mss

keepepEuropeurope w

ettwith mildith mild

tempeemper

aturetures

Atlanticstorms keepEurope wetwith mild

temper

atures

Mild weatherdominates eastof the Rockies

Strong windscircling the

arcticcold air

Winds aroundarctic are

weak and thecold air canmove south

he main culprit behind this winters snow andcold is a natural change in an arctic windpattern.

Some years it blows strong and tightaround the top of the Earth, holding in muchof the cold air. This year, the pattern has been

looser, and more of that cold air has slipped free and

ridden a jet stream directly into the Louisville area anddeeper south.Meanwhile, barreling in from the west below us was the

jet stream from El Nio and the moisture it picked up inthe Pacific.

When the upper edge of that warm, moist air from thewest met the frigid arctic air, snow fell from the sky. WhileEl Nio took much of its moisture south of Louisville, theair was cold enough to make more snow than normal.

Why allthe weirdweather?

Frigid arctic air

Frigid arctic air

The main cause: Arctic oscillation

Other factors: El Nio and the jet stream

Louisville weather: By the numbers

Warm phase

Cold phase(what happened this winter)

Wiae

co

Frigid arctic air

Cold

In the warm phase, higherpressure at mid latitudesdrives ocean storms farthernorth. Changes in thecirculation pattern bring

wetter weather to Alaska,Scotland and Scandinavia,as well as drier conditionsto the western UnitedStates and theMediterranean.Frigid winter air doesnot extend as far intothe middle of NorthAmerica as it wouldduring the coldphase of theoscillation.

Relatively high pressure over the polar regionand low pressure at mid latitudes. Weatherpatterns in the cold phase are, ingeneral, "opposite" to thoseof the warm phase.

El Nios cycle of warming up the equatorial waters in the eastern Pacific occurs every three to sevenyears and affects weather around the globe. In the United States, a moderate El Nio makes winterwetter and cooler across the southern third of the country and warmer and drier across the North.

Cold

Warm

Dry

Strcir

rigid arctic air

SUNDAY PRINT EXCLUSIVE

Sources: National Snow and Ice Data Center.; NOAA; University of Washington;National Weather Service; the University of Louisville By Steve Reed, The Courier-Journal

+3 +4+2+10-1-2-3

Unusual temperaturesHow temperatures differed from normal over the last three months

Celsius

P ci c

cean

years and affects weather around twetter and cooler a ross the south

Atlantic

Ocean

Frigid arcticair with

snow

Cold blastsbring snowand ice to

Europe

toe

Atlantic

Ocean

Atlantic

Ocean

0 +1-1 +2-2-3-4-5 +3 +4 +5

More snow ... ... less liquid precipitation

Colderolderthanhan

normalormal

Colderthan

normal

Warmerarmerthanhan

normalormal

Warmerthan

normal

Warmerarmerthanhan

normalormal

Warmerthan

normal

Dry here,wet there

Percentof normal

forJanuary

2010Wetteretter

than normalhan normal

Wetterthan normal

Wetteretterthan normalhan normal

Wetterthan normal

Wetteretterthan normalhan normal

Wetterthan normal25%

50%

75%

125%

150%

175%

In inches In inches compared with normal

Dec. December 2009 January February

0.37.1

12.7

20.1

2.85 2.851.86

14.6

Jan. Feb . Total Normal

2009 2010

2009 2010

0.84 0.43 0.5

The global picture

Temperaturedifference

fromnormal for

January 2010

In inches

15.5

5.7

10.6 10.7

19.8

11.1

19.8

3.6 4.8 4.55

Calendar year

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010*

Annual snow history

*Through Feb. 23

Winter temperatures

Dec. Jan. Feb.

36.630.1 29.9

43.829.9

24.9 28.536.6 36.2

Average temperature, and departure from normal

All day average High Low

-1.0 -2.9 -7.7 -1.6 -4.4 -9.4 -0.5 -1.4 -6.0

2009 2010

Dec. Jan. Feb.

2009 2010

Dec. Jan. Feb.

2009 2010

Annabelle Ott, 5, left, and Lizzy Tiano, 10, roll a huge mound of snow as they build the trunk ofsnowman at the Westport Village.

By Sam Upshaw Jr., The Courier-Journal

Drierrierthan normalhan normal

Drierthan normal

Drierrierthan normalhan normal

Drierthan normal

Though climate-change skeptics have pounced on the cold weather, scientists point out that a fewweeks of snow in one area of the globe have nothing to do with the long-term climate changesaround the world . And while it might have been frigid locally, it's been unusually warm in many otherparts of the world.

Warmer and drier

Warmerand drier

Colder anddrier

Colder andwetter

Colder andwetter

Colderand

wetter

Pacificjetstream