Deadly winter storm grips U.S.
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A huge winter storm sweeping across the southern United States has killed at least 30 people and left millions without power
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TEMPERATURES (February 17, 07.00 EST)

-10 0 10 20 30 40 50 60 70 F
-20 -10 0 10 20 C

OREGON
States reporting deaths
OHIO MISSOURI
Dallas
KENTUCKY
NORTH CAROLINA
LOUISIANA
Houston

TEXAS: Four million without power, 1.4m in Houston alone. Blackouts in 25% of homes in Dallas

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Polar vortex: Spinning pool of cold air normally circles stratosphere over North Pole. Circulation can weaken in winter, causing surges of frigid air to splinter
off and drift south
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STABLE POLAR VORTEX
Strong jet stream
Cold air contained

WAVY POLAR VORTEX
Cold air moves south
Warm air moves north
Weak jet stream
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Sources: Reuters, National Weather Center, NOAA
Picture: National Weather Center
© GRAPHIC NEWS


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