"Explain briefly the ENSO pattern and its impact on US winter weather thus far."

ENSO stands for El Niño-Southern Oscillation, a climate pattern that occurs in the tropical Pacific Ocean and influences weather around the world, including the US winter weather. ENSO has two opposite phases: El Niño and La Niña.

• El Niño is characterized by warmer-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. This can lead to more moisture in the atmosphere, influencing the jet stream and often causing warmer temperatures and increased rainfall in the southern parts of the United States during winter. The northern regions may experience drier and milder conditions.
• La Niña, on the other hand, is marked by cooler-than-average sea surface temperatures in the same area of the Pacific. It tends to have somewhat opposite effects on the US winter weather compared to El Niño, bringing cooler and wetter conditions to the northern US and drier, warmer weather to the southern part.

ENSO also varies in intensity, which means its impacts on US winter weather can be stronger or weaker depending on the strength of the El Niño or La Niña event.