Today NOAA put out a La Niña Advisory for conditions in the eastern Pacific Ocean. This advisory replaces the La Niña Watch that has been active on and off for the last few months. This means that colder than normal water temperatures have been present along the equator in the eastern Pacific Ocean for long enough that NOAA can say a La Niña has officially begun.
So far this event looks like a weak one, but it is expected to last for several months, which means that warmer and drier conditions than normal are more likely to happen statistically in parts of the Southeast including south Georgia and Alabama and into Florida. In a weak La Niña, effects on northern parts of the region are less certain. You can read the NOAA story at https://www.noaa.gov/news/hello-la-nina. They also describe more about the process of declaring a La Niña in their blog at https://www.climate.gov/news-features/blogs/enso/november-2016-la-ni%C3%B1a-update-hello-lady.
This La Niña follows one of the strongest El Niños on record. After past strong El Niños, La Niña has been known to reoccur for two or even three years in a row, so this will bear watching. A La Niña is one of the precursors of drought in the Southeast (and this year’s conditions have probably contributed to our current drought) so 2017 could be an interesting year.
One thing that is curious about this year’s La Niña is that while sea surface temperatures along the equator are quite cold, the water just to the north is still quite a bit above normal. This is not generally the case with La Niña and so it will be interesting to see how this affects the weather patterns in the coming months.
