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Is another big La Nina on the way?

Another big La Nina could mean another cold winter for the Northern USA, and another wet flooding summer with potentially nasty cyclones for Eastern Australia (and the rest of the Eastern Pacific nations). La Ninas even affect the Indian Monsoon Season. If only we could predict them accurately.

Frank Lansner on HideTheDecline has noticed that one set of models (NCEP/CFS) is predicting a large La Nina brewing, while most of the others are still forecasting “neutral” conditions. The NCEP/CFS models were more accurate last year. If they are right now, we could be in for a large La Nina. On the other hand, Australia’s Bureau of Met is predicting only that “La Nina remains possible in 2011”.

Guest Post: Frank Lansner

Another Large La Nina Imminent?

For months the NCEP/CFS has been predicting a stronger second La Nina dip. Prior to the last La Nina, the NCEP/CFS was much better at predicting the La Nina — and personally I feel confident with the NCEP/CFS Prediction. It does seem to suggest that a La Nina will be upon us in a very short while. If so, global cooling is likely to shift into a faster gear.

Cooler water is appearing in the Eastern Pacific:

fig 1. A quick look at the Unisys SST shows the beginning of potential La Nina signs.

fig2. The blue runs are the newest, the red the oldest. This means that NCEP/CFS is shifting to forecasts of stronger La Ninas. But look at how fast things are moving. Below: The July – August – Sept forecasts are dropping as a La Nina becomes more likely.

Fig 3: A look under the Pacific equator reveals more cold from beneath. This cold area does not seem to import cold water from west (as for the last La Nina dip), the cold area just grows bigger, apparently being supplied with cold water from elsewhere.

Franks original post has a few more details on HideThe Decline.


Post Note from Jo

The Australian BOM forecast is very different and decidedly neutral. It will be interesting to see which way this goes.

The Australian BOM August 31, 2011:

Trends over the past fortnight include further cooling of the central Pacific Ocean, persistent positive Southern Oscillation Index (SOI) values and stronger than normal trade winds. However, cloud patterns are currently close to normal, and all indicators remain well short of the strong La Niña conditions evident at the same time last year.

“It’s worth noting that since 1900, about half of all La Niña events re-emerged in the second year. Further cooling of the central Pacific Ocean coupled with persistent positive SOI values in the next few months would further increase the chance of a La Niña event at the end of 2011.”

The latest SOI figure is only 2.8 (it needs to be above 8 to indicate a La Nina.)

The Sea-Sub surface graph at the BOM site shows the cold water increasing in the Eastern Pacific.

May 2011 (top) - August 2011 (bottom): Cooler water is appearing in the Eastern Pacific

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