El Nino & La Nina Explained

In normal years, trade winds blow from

• 
  

• north to south

• east to west

• south to north

• west to east

During normal or non-El Nino years, 

• • warm surface waters are pushed eastward in the tropical Pacific Ocean by the trade winds

• • warm surface waters are pushed westward in the tropical Pacific Ocean by the trade winds

During an El Nino,

• 
  

• • the trade winds weaken or reverse direction and warm water flows eastward in the Pacific, reducing upwelling of cold water along South America.

  
  

• • the trade winds blow stronger moving warm water westward towards Indonesia, increasing downwelling along Indonesia.

  
  

How does El Nino affect weather in the United States?

• 
  

• • More rain and flooding in the eastern U.S. and warmer, drier conditions in the western U.S.

  
  

• • More flooding in the southern U.S. and warmer, drier conditions in the Pacific Northwest and northern U.S.

  
  

What happens to warm surface water in the Pacific Ocean under normal conditions?

• Moves eastward

• Stays in the center

• Moves westward

• Disappears

What is El Niño characterized by?

• Stronger trade winds

• Colder ocean temperatures in the Eastern Pacific

• Weakened trade winds and eastward movement of warm water

• Increased upwelling of cold water

How does El Niño typically affect weather patterns in the Southern United States?

• Cooler and drier conditions

• Flooding

• Drought

• Heavy snowfall

What is a key characteristic of La Niña?

• Weakened trade winds

• Warmer ocean temperatures in the Eastern Pacific

• Stronger trade winds and increased upwelling of cool water

• Southward shift of the Jet Stream

What weather condition is typically associated with La Niña in the Southern United States?

• Flooding

• Heavy rains

• Drought

• Warmer temperatures

La Nina causes

• • more upwelling of cold water in the eastern Pacific near South America

  
  

• • more downwelling of warm water in the eastern Pacific near South America

  
  

• • More upwelling of cold water in the western Pacific near Indonesia