Weather Blog

Overall La Nina forecasts unchanged, but there are subtle hints

Overall La Nina forecasts unchanged, but there are subtle hints

NOAA released its weekly update on the status of the whole La Nina/El Nino cycle Monday, and are sticking with the recent forecast that neutral conditions are going to remain through November, but it's 50/50 whether we'll then stay neutral or go toward La Nina.

But other signs remain that La Nina's odds might soon trend a bit higher and with it, the odds of another cooler and wetter than normal fall and winter.

* The current temperature anomaly in the area of the Pacific Ocean where La Nina/El Nino's average is calculated is currently at -0.6C, after reading -0.7C last week. A La Nina reading is considered anything below -0.5C, but to be classified as a true La Nina event, the running three-month average has to average -0.5C or lower for three consecutive months -- as in a May-June-July would be one period, then June-July-August would be a second -- get three of those in a row under -0.5C and it's a La Nina.

The last running average posted in May-June-July and it was smack dab average at 0.0C difference so we are officially neutral at the moment. That comes off a -0.2C reading for April-May-June. But the trend is heading down and it'll be interesting to see when the June-July-August number gets posted whether it is trending negative again -- an ominous sign of La Nina if so.

And check out this graph, which shows the trend of the past year, also suggesting a cooling trend.

* A spread of 25 forecast models still have a majority predicting neutral conditions, but more are starting to lean toward La Nina starting in November. The July spread had just four predicting averages of -0.5C or lower, but in August, now eight models are predicting -0.5C or lower starting in November.

* Another new "Climate Forecast System" model that was built and put into action in March, with predicting the El Nino cycle in mind, is solidly predicting La Nina conditions -- some of its forecasts even have it on par to perhaps even a little stronger than last winter's version.

* Some of the longer 30 and 90 day forecasts are beginning to believe it as well. The latest versions issued a little earlier this month are now predicting a better chance of a wetter than normal autumn, and a better than even chance of a wetter and cooler than normal winter - both hallmarks of La Nina:

90 day forecast for September, October and November:

90 day forecast for January, February and March:

So while officially, NOAA is sticking with neutral through November, then "50/50 neutral or La Nina", if I were betting, I'd perhaps put my chips down on the La Nina's side.