Outstanding Operational Forecast Challenges Board

Predicting 2011/12 La Niņa onset by models  — Where was the early warning?

In CPC Sanity Check of November 2011, the failure of Nino 3.4 SST forecast from June initial condition by almost all models was brought to attention with two exceptions of good forecasts by ESSIC Intermediate Coupled Model (ICM) and by Japan Frontier Research Center for Global Change Coupled General Circulation Model. Looking at individual model performance, a common problem of phase delay in prediction of ENSO transition is clearly shown.

Question:  What key physical processes were missed or misrepresented?

CPC Ocean Monitoring Group made a quick examination on some key ocean and atmosphere conditions and provided some clues as follows.

i)    "Most of models forecast ENSO-neutral conditions in summer/fall 2011 from spring 2011, probably due to unrealistic response to positive heat content anomaly in the tropical Pacific and failure in capturing the persistent easterly wind anomalies in the central Pacific."

ii) "Although the tropical Pacific returned to ENSO-neutral conditions during May-Jul 2011, persistence of easterly wind anomalies in the western-central Pacific and the enhanced (suppressed) convection persisted in NW Pacific (south central Pacific) probably were related to the persistence of horse-shoe pattern of negative SSTA. To be able to forecast the onset of La Niņa from spring, models need to be able to maintain the horse-shoe SSTA and eastern wind anomalies."  

The above plots and analysis are taken from the CPC's Monthly Ocean Briefing PPT (http://www.cpc.ncep.noaa.gov/products/GODAS). The CPC makes a monthly assessment of how the state of the global ocean evolved recently; what was the interaction with the atmosphere; and how model predictions verified. This assessment is disseminated using a PPT presentation and conference call around the 7th day of each month. Contact Yan Xue if you wish to be added to the Monthly Ocean Briefing listserv.

ESSIC ICM represents an intermediate coupled model (ICM) developed by the Earth System Science Interdisciplinary Center (ESSIC), Univeristy of Maryland. For more information about ESSIC ICM , contact Rong-Hua Zhang at rzhang@essic.umd.edu