1. El Nino and La Nina An important atmospheric variation that has an average period of three to seven years. Goes between El Nino, Neutral, and La Nina (ENSO cycle, El Nino Southern Oscillation) Has large influence both in the tropics and midlatitudes. Main source of forecast skill beyond a few weeks.

4. An Important Measure is the Temperature in the Tropical Pacific

5. Niño Region SST Departures ( o C) Recent Evolution The latest weekly SST departures are: Niño 4 -0.6ºC Niño 3.4 -1.1ºC Niño 3 -1.2ºC Niño 1+2 -1.3ºC

6. Why do we care? The circulations in the midlatitudes are substantially different in El Nino, Neutral, and La Nina years. Since the temperature of the tropical Pacific changes relatively slowly, this gives some meteorologist some insights into the weather over the next several months.

7. El Nino – weak Aleutian High

8. La Nina – strong Aleutian High

11. Great Web Site on ENSO: Climate Prediction Center http://www.cpc.ncep.noaa.gov/p roducts/precip/CWlink/MJO/ens o.shtml http://www.cpc.ncep.noaa.gov/p roducts/precip/CWlink/MJO/ens o.shtml