Scientists are carefully monitoring sea-surface temperatures in the tropical Pacific Ocean for a potential El Niño event. An El Niño occurs when warmer-than-average waters start to form in the eastern Pacific Ocean, specifically near the equatorial latitudes. Easterly winds (blowing from the east) typically move warmer water to the western Pacific (near Indonesia), permitting cooler water to upwell to the surface in the east (near South America). When these winds are weaker, or if they reverse direction, the warm water stays in the eastern Pacific. This difference in sea surface temperatures and winds creates a new dynamic between the ocean and atmosphere, distinctly affecting weather patterns across the world. No two El Niño events are alike; they vary in magnitude and location of the largest temperature anomalies. El Niño events can be classified as Strong, Moderate or Weak.