NOAA - La Nina Returns; Continued SW Drought, Cold Across The North, More Spring Tornado Activity

[hatrack]

After a months-long period of relative atmospheric balance between El Niño and La Niña, the National Oceanic and Atmospheric Administration announced Thursday that La Niña has returned. It’s expected to stick around in some capacity through the winter and relax toward spring.

The intensifying La Niña should peak in magnitude, or strength, by the end of 2021, having bearings on the drought in the West, the end of hurricane season and the upcoming winter. La Niña also plays a role in shaping how tornado season pans out in the spring. It’s one of many drivers in our atmosphere, but it is often among the most important given the extent to which it shuffles other atmospheric features key in determining how weather evolves over the Lower 48.

EDIT

https://www.washingtonpost.com/wp-apps/imrs.php?src=&w=916

La Niña begins with a cooling of waters in the eastern tropical Pacific. The basin alternates between El Niño and La Niña every two to seven years on average. That pocket of cooler ocean water chills the air above it, inducing a broad sinking motion. It’s that subsidence, or downwelling of cool air, that topples the first atmospheric domino. During La Niña winters, high pressure near the Aleutian chain shoves the polar jet stream north over Alaska, maintaining an active storm track there. The Last Frontier often ends up cooler than average. The confluence of the polar and Pacific jet streams, as shown in the image above, helps drag some of that cold air across the Pacific Northwest and adjacent parts of the northern Plains.

That keeps the northern United States anomalously wet, while the South is left largely warm and dry. This is bad news for California and other parts of the Southwest, which are enduring a historic drought. The persistence of warm, dry conditions would cause the drought to worsen and potentially prolong the fire season.

EDIT

https://www.washingtonpost.com/weather/2021/10/14/la-nina-winter-forecast/

[AllaN01Bear]

1. interisng that we in sonora have 88% chance of rain tonite.