(WLNS) – An El Nino is a teleconnection (a forecasting tool to link a circulation or pressure difference to a longer range forecast). Typically in the winter, you may hear a meteorologist mention the NAO (north american oscillation or the AO (Arctic Oscillation) to predict cold weather and storms. These oscillations use pressure differences to give an idea what the jet stream will look like in the near future. The jet stream is an important factor on where warmer or cooler air sets up and in what direction storms track.
The ENSO (El Nino Southern Oscillation) uses water temperature anomalies around north western South America to decide the phase; either warm waters (El Nino) or cool waters (La Nina).
You can see the warmer water “tongue” in NW South America. This indicates an El Nino is taking place. The warm waters in the east towards South America lowers the pressure and water flows W to E from Australia in a strong current. This causes the jet stream to shift and affects weather around the world. Below is a map by NOAA describing typical changes in in temperatures and moisture from an El Nino. Notice the drier, warmer air here in Michigan. Also, the shifts in jet streams as the polar jet ( the one that typically dips south and brings cold shots of weather from Canada) has trouble making it south and a warmer, moist tropical jet extends through the southern half of the country.
*The fact that it is considered a strong El Nino, you notice the typical conditions (warm temperatures) are more likely:
Here is a statement from the Climate Prediction Center issued yesterday: CPC Synopsis: There is a greater than 90% chance that El Niño will continue through Northern Hemisphere winter 2015-16, and around an 80% chance it will last into early spring 2016.