Aside from the brief shot of cold, arctic air late last month that dropped temperatures well below average, dry and mild conditions have prevailed across much of the Gulf Coast (and Southern U.S.) for much of the fall season thus far.
La Niña: the reason for the dry, mild conditions
This is not unprecedented, as there is an ongoing La Niña event in the Pacific; it was officially declared yesterday. During a La Niña, warmer than average temperatures and dry conditions typically dominate the South.
Though the La Niña was officially declared yesterday, the atmosphere has been in a La Niña state for some time, which is reflected by the aforementioned dry and mild conditions that have prevailed across the Gulf Coast, and Southern half of the country as a whole.
Cold and stormy for Thanksgiving Week?
Even in a La Niña event, there can be periods of stormy and cold weather, as well as below normal temperatures, across the Gulf Coast and Southern Tier of the U.S. in the fall and winter driven by atmospheric teleconnections. And it appears just such a period could occur around Thanksgiving week.
As of the latest forecasts (see image above), both the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expected to go into negative phases late next week. If this occurs, it would favor below normal temperatures and stormy conditions returning to the Eastern third of the country, as well as portions of the Central part of the country, around the week of Thanksgiving.
Model guidance has already begun to pick up on this, with the ECMWF advertising a rather potent storm system to bring cold, arctic air and stormy weather to the Eastern and Central U.S. (including parts of the Gulf Coast) between the 17th – 20th time frame.
ECMWF is beginning to latch on to the idea of a rather potent storm system bringing cold, arctic air and stormy weather to the Eastern and Central U.S. in the 8-10 day time frame. Not unrealistic, as the NAO and AO are expected to be negative. pic.twitter.com/hO45zYcb9E
— Gulf Coast Storm Center (@GCSCWX) November 9, 2017
The GFS is also advertising a storm system to bring cold, arctic air and stormy weather to the Eastern and Central parts of the country, but slightly later, during the 20th – 23rd time frame.
Uncertainty
While it is fairly certain at this point that at least some colder and stormy weather will return Thanksgiving week, some uncertainty remains, and it is too early for specifics.
This is because it is too early to ascertain the exact timing and potential strength of any storm systems, as well as the strength and extent of any outbreaks of frigid arctic air that might spill south out of Canada.
___
For future updates follow us on our social media:
