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Probabilistic Predictions of ENSO Indices Using Statistical Models

The forecast probabilities averaged across 7 models are presented in the graphs and tables below. The graphs show the probabilities for "cold" (blue), "neutral" (green), and "hot" (red) conditions, and the horizontal lines indicate the climatological probabilities (25% each for "cold" and "hot", and 50% for "neutral"). The forecasts were produced using April 2003 observed sea-surface temperatures, and with version 4.01 of the SPEP (Statistical Probabilistic ENSO Predictions) model.
NINO1&2
Month lead-time cold neutral hot
May 2003 0 68% 21% 11%
Jun 2003 1 97% 2% 0%
Jul 2003 2 97% 3% 0%
Aug 2003 3 98% 2% 0%
Sep 2003 4 94% 6% 0%
Oct 2003 5 69% 21% 10%
Nov 2003 6 80% 20% 0%
Dec 2003 7 91% 8% 1%
Jan 2004 8 35% 55% 10%
Feb 2004 9 41% 48% 11%
Mar 2004 10 25% 59% 16%
Apr 2004 11 18% 60% 22%


NINO3
Month lead-time cold neutral hot
May 2003 0 57% 14% 29%
Jun 2003 1 58% 26% 16%
Jul 2003 2 57% 13% 31%
Aug 2003 3 58% 8% 34%
Sep 2003 4 71% 20% 9%
Oct 2003 5 63% 21% 16%
Nov 2003 6 72% 14% 13%
Dec 2003 7 68% 29% 3%
Jan 2004 8 42% 32% 27%
Feb 2004 9 16% 54% 30%
Mar 2004 10 60% 23% 17%
Apr 2004 11 37% 39% 23%


NINO3.4
Month lead-time cold neutral hot
May 2003 0 43% 53% 4%
Jun 2003 1 87% 13% 0%
Jul 2003 2 73% 26% 1%
Aug 2003 3 79% 20% 1%
Sep 2003 4 78% 21% 1%
Oct 2003 5 68% 27% 5%
Nov 2003 6 69% 28% 3%
Dec 2003 7 64% 34% 3%
Jan 2004 8 54% 39% 7%
Feb 2004 9 41% 53% 6%
Mar 2004 10 55% 43% 3%
Apr 2004 11 42% 47% 11%


NINO4
Month lead-time cold neutral hot
May 2003 0 44% 53% 3%
Jun 2003 1 63% 34% 3%
Jul 2003 2 74% 25% 0%
Aug 2003 3 76% 23% 1%
Sep 2003 4 78% 21% 1%
Oct 2003 5 74% 24% 3%
Nov 2003 6 68% 30% 2%
Dec 2003 7 66% 34% 1%
Jan 2004 8 62% 36% 2%
Feb 2004 9 39% 53% 9%
Mar 2004 10 42% 52% 6%
Apr 2004 11 42% 51% 6%