La Nina’s back. Here’s what it will do to your weather this winter

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What You Need To Know: La Nina

This week, weather officials announced that the  La Nina climate pattern has arrived.
If you are not sure how to react to that news, you are not alone.

Officials with the National Oceanic and Atmospheric Administration said Thursday a weak La Nina has formed and is expected to stick around for several months.

La Nina is a natural cooling of parts of the Pacific, and the phenomenon is a major factor in weather around the world as we move into late fall, through winter and into spring.

Here’s what the return of La Nina means.

How is it formed?

According to National Geographic, La Nina is formed "by a build-up of cooler-than-normal waters in the tropical Pacific, the area of the Pacific Ocean between the Tropic of Cancer and the Tropic of Capricorn. Unusually strong, eastward-moving trade winds and ocean currents bring this cold water to the surface, a process known as "upwelling."

What does “La Nina” mean?

  • La Nina means "the little girl"
  • La Nina's full name is El Nino-Southern Oscillation (ENSO)
  • It is the counterpart of El Nino – a pattern that warms waters in the Pacific

What happens in La Nina years?

  • During periods of La Nina, sea-surface temperatures across the equatorial eastern central Pacific Ocean will be lower by 3 to 5 degrees centigrade.
  • La Nina brings warmer-than-normal sea-surface temperatures to the southern Pacific Ocean around northern Australia, New Guinea and the islands of Indonesia.
  • The pattern generally lasts around five months.
  • La Nina causes above-average precipitation across the northern Midwest, the northern Rockies, Northern California, and the southern and eastern parts of the Pacific Northwest.
  • It will be dryer in the Southwest and Southeast.
  • It triggers stronger-than-average hurricanes in the Atlantic and fewer hurricanes in the Pacific.
  • The Southeast and Mid-Atlantic will see warmer-than-average temperatures during a La Nina winter.
  • In Canada, La Nina brings more cold and more snow.
  • This is the second consecutive La Nina winter.
  • Last year's episode lasted only from November to February which was unusual.
  • Texas A&M University agricultural economist Bruce McCarl told USA Today that La Nina years are often bad for agriculture in Texas. The same goes for other parts of the United States during a La Nina year.

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