Long-term Climate Predictions for NIDIS Pilot Projects

While the NOAA Climate Prediction Center (CPC) makes frequent use of well-known ENSO-associations with U.S. climate, their seasonal forecasts do not extend beyond 15 months. In fact, due to a lack of consensus in ENSO-prediction models beyond about six months, it is very rare for CPC to issue ENSO-based forecasts for the latter half of their forecast range. Since water managers sometimes have to make planning decisions beyond the one-year time frame, especially for large western reservoirs, this is not helpful.

Historically, there is an asymmetry in the duration of ENSO events that allows some La Niña events to outlast their El Niño counterparts. In prior research, it was found that the bigger the peak amplitude of a La Niña event, the longer it typically lasts – the two most energetic La Niña events since 1950 (1954-57, and 1973-76) also lasted about three years. In contrast, the three biggest El Niño events of the last 150 years (1877-78, 1982-83, and 1997-98) lasted 1.5 years at most.

When the 2010-11 La Niña reached a substantial peak by late 2010, it offered the opportunity to test this notion within the context of the Upper Colorado as well as the Apalachicola-Chattahoochee-Flint (ACF) NIDIS Pilot Projects. This presentation will discuss typical impacts of two-year La Niña events on runoff in the Colorado River basin, as well as long-term precipitation anomalies in the ACF region. A progress report on observed conditions will be given as well.