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Summary of CFS ENSO Forecast

May 2010 update

Mingyue Chen, Wanqiu Wang and Arun Kumar

Climate Prediction Center

1. Latest forecast of Nino3.4 index (slide 2)

2. Hindcast skill of Nino3.4 index (slide 3)

3. Hindcast scatter plots of Nino3.4 index (slide 4)

4. Verification of forecast for April 2010 and FMA 2009-2010 (slides 5-14)

Outline

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The forecasts from the latest initial conditions show that the Nino3.4 near normal condition will be transitioned to cold conditions during next 2 months and maintain the cold phase afterward. The PDF corrected forecasts show smaller amplitude of ensemble means from Jul to Oct 2010. The spread of the PDF corrected forecasts is smaller throughout the forecast period..

Latest Nino3.4 SST forecast from May 2010

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RMSE (K)

PDF corrected

RMSE (K)

Hindcast skill of Nino3.4 index from May initial conditions

PDF correction shows smaller (larger) RMSE during Jul to Sep (Oct-Feb). Correlation skills of PDF corrected are slightly lower.

Correlation

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Hindcasts of JAS Nino3.4 index from May initial conditions

Raw anomalies PDF corrected anomalies

PDF correction improves JAS forecasts from May.

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Verification of CFS Forecast for April 2010 and FMA 2010

Nino34 SST: Nino3.4 SST April 2010 forecasts are too warm from initial conditions of Nov 2009 -Jan 2010 and are close to observation from initial conditions of Feb – Mar 2010 (slide 7).

Spatial SSTs: The CFS over predicted the warmth in the tropical E. Pacific and SE Pacific but under predicted the warmth over the tropical Atlantic in the forecasts from Nov 2009 – Jan 2010. The magnitude of the forecast errors were much reduced in the forecasts from Feb-Mar 2010 (slides 8-9).

Taux and subsurface temperatures: Consistent with the errors in SST, the CFS produced large westerly errors in the central tropical Pacific in April 2010 forecasts from Nov 2009 to Jan 2010. The Apr 2010 forecasts also showed warm errors in subsurface temperature east of the Date Line (slides 8-13).

Impacts of intraseasonal variability: The westerly anomalies in late Jan and early Feb 2009 in the central Pacific appeared to have led to the continued westerly anomalies in the Eastern Pacific in the forecast. Conversely, the strong easterly anomalies in the western and central Pacific around the end of Apr may have contributed to the sustained easterlies and thus colder SSTs in the forecasts (slide 7 & 14).

Analysis of forecast for April 2010 from previous initial months

FMA 2010 Nino3.4 forecast ensemble means are too warm from initial conditions of Sep to Nov 2009, and are close to observation from initial conditions of Dec 2009 –Jan 2010 (slide 6).

Verification of FMA 2010 Nino34 SST forecast at different leads

For FMA 2010 as the Target; Forecasts From Different Leads

4-month Lead from Sep

3-month Lead from Oct

2-month Lead from Nov

1-month Lead from Dec

0-month Lead from Jan

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