The big news out of the El Niño update for August is that the odds of a fall or winter event has dropped to 65% (from 80%). Australia’s Bureau of Meteorology even lowered their prediction to 50%. Several headlines I saw seemed to focus on that numerical change. Yes, 65% is indeed lower than 80%, but the odds still are pointing to a coming El Niño event. Plus, the odds remain about double that of any given year.
More importantly, the forecast is for a weak or moderate event (“a strong El Niño is not favored in any of the ensemble averages”). On the plus side, you can probably stash away your gold bullion and dehydrated food packets for the next apocalypse. But, there still are plenty weather-related crises to fret over: California drought, Detroit flooding, or Hawaii tropical cyclones.
In short, an El Niño event is slightly more likely this summer (70% chance vs. 65%) or fall/winter (80% chance). The models currently predict a moderate strength event (+1.0°C to +1.4°C), but Dr. Ventrice is expecting the higher end at +1.5°C. For comparison, the lower limit of an El Niño event is +0.5°C and the “Super” El Niño of 1997-8 was +2.5°C. But, everyone put lots of caveats on these modeled results as estimating the strength of an event is much more difficult than the likelihood of one.
Regardless, Dr. Ventrice emphasizes, “Regardless of what amplitude the ENSO 3.4 Index [ed. El Niño strength] achieves, it only matters if the atmosphere responds.” (Emphasis in original.) His point is that while the Pacific Ocean is highly likely show El Niño-like temperatures, the impact on North America and the Atlantic hurricane season may not appear until August or later. That means there could be heat waves in the central and eastern continental US, continued drought in California, or regular Atlantic hurricanes until the atmosphere “feels” the effects.
* I recommend the Australian website as the easiest to read and understand. CPC’s updates are also good, but can take a few weeks or months to get the hang of the lingo. Dr. Ventrice’s posts are probably the most technical, but also provide excellent coverage into how an El Niño develops and what to watch for in the data.
NOAA’s Climate Prediction Center (CPC) has issued their monthly El Niño diagnostic discussion for May 2014 (permalink). The summary has increased the probability of an event from “exceeding 50%” to “exceeding 65%”. The CPC and International Research Institute (IRI) provides a quick look at the longer term forecasts, which peak at 78% to 79% for Nov or Dec of 2014. The Australian Bureau of Meteorology also issued their bi-weekly update on Tuesday, which cites the likelihood of an El Niño at least at 70%. As the more detailed discussion at Real Climate notes, even with an 80% prediction, there still is a 20% chance that an El Niño will not form.
At this point, however, the more interesting discussion is the forecast intensity. Currently, the average of all the models have the event peak at around 1°C (with the highest model at 1.5°C). This is significantly less than the record-breaking El Niño events in 1983 and 1997-8 of nearly 3°C. The expert discussions are careful to note that strength forecasts at this point are highly unreliable, so there is no guarantee that this will either be an especially mild or strong event.
Like NOAA in the US, Australia’s Bureau of Meteorology periodically provides status updates on El Niño conditions and related climate conditions. Today’s update is similar to NOAA’s weekly update, so there isn’t much to add. However, their graphical summary of ENSO models is a little easier to read than NOAA’s. The exact underlying data is different, but the trend and forecast is similar.