Saturday, March 7, 2015

Long Range Climate Models Forecast El Nino Development in Summer, Fall

After a failed El Nino prediction for this winter, despite the NOAA declaration of the phenomenon in the last few days, model guidance is once again forecasting an El Nino developing in the summer and fall.

The above image shows the sea surface temperature deviation from normal, centered over the central Equatorial Pacific, forecasted until late 2015. The red line shows observed anomalies to date, while the yellow boxes portray the range of SST anomalies in the forecast period. This particular forecast sees water temperatures warming steadily from late spring into the fall, when the average of the boxes reaches 1.0ยบ C at the very end of the forecast period.

The next forecast, from the Australian Bureau of Meteorology, shows temperatures quickly warming up from mid-spring onwards, solidly in El Nino territory by the early winter of 2015-2016. This was another model that consistently forecasted an El Nino this past winter, but never verified. It's quite possible we see this happen again this summer and fall.

The atmosphere is, right now, quite conditioned for an El Nino to develop. We have been seeing sustained negative values from the Southern Oscillation Index (SOI), an indicator of El Nino conditions in the atmosphere. This winter, it didn't come out as expected. However, if we keep a similar SST set-up across the Pacific, as well as our pre-conditioned environment for the El Nino, we could see that develop. I remain pretty skeptical, however.

To summarize:

- Model guidance is projecting an El Nino to form for the summer and fall months.
- Because the majority of model guidance was incorrect in their forecasts this past winter, uncertainty is extremely high.