La Nina: What it means for the Tri-State

The Australian Government Bureau of Meteorology announced in early August, that the Pacific Ocean was officially in the early stages of La Nina. 

Temperatures have been steadily cooling in the central and eastern sections of the tropical Pacific Ocean since January 2010. In fact, temperatures are now more than 1 degree Celsius cooler than normal for this time of year.

There is one small area near 150 W along the equator that is almost 3 degrees Celsius cooler than it typically would be. 

Last year, the Tri-State had a colder and snowier winter than normal.  We were in the midst of El Nino, which is a period of warmer than normal waters in the central and eastern tropical Pacific Ocean. 

La Nina usually lasts around a year, but it can be shorter or longer. 

You can also look at the Southern Oscillation Index (SOI) to determine if there is an El Nino or a La Nina.  A positive SOI indicates that conditions are favorable for La Nina conditions while a negative value indicates El Nino.

The SOI is a measure in the difference of pressure between Tahiti in the French Polynesia and Darwin located in the Northern Territory of Australia.

La Nina brings drier than normal conditions to the Southwest during late summer.  The Central plains sees below average precipitation in the fall and the southeast is drier than normal during the winter.  

The Pacific Northwest has above average precipitation during the later fall and early winter winter months.  During a La Nina winter, temperatures are above normal in the southeast and below normal in the Northwest.