Final Winter 2011-2012 Outlook

Even though we are still in the 2011 Hurricane Season it is that time of the year where we have to start talking about the Winter of 2011-2012 and its likely outcome.

In order to get a proper perspective on the Winter of 2011-2012 we have to look at some important teleconnections. These teleconnections drive our weather across the globe.

The Pacific Decadal Oscillation

The above image shows the warm phase and the cool phase of the PDO and we are currently in the cool stage or negative phase. Most recent PDO reading was negative 1.86 (click here)

Southern Oscillation Index

Sustained negative values of the SOI often indicate El Niño episodes. These negative values are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in rainfall over eastern and northern Australia.

Positive values of the SOI are associated with stronger Pacific trade winds and warmer sea temperatures to the north of Australia, popularly known as a La Niña episode. Waters in the central and eastern tropical Pacific Ocean become cooler during this time.

As you can see from the image above we are currently experiencing positive SOI which is indicative of a La Nina.

Global Atmospheric Angular Momentum

GLAAM above is negative which is also very indicative of a La Nina. This should also lead to a – QBO for the winter of 2011-2012 as well.

Now moving on to the other teleconnections:

North American Oscillation

You can see that overall thru August the NAO has been running negative. Though the NAO will fluctuate and at times go positive the overall trend of a Negative NAO should continue..

On the 500mb level, the most common influence of the NAO occurs over Greenland. A low pressure area nearby supports a piece of the Polar Vortex getting cutoff over the region in a positive NAO. The displacement of the PV makes it a lot easier for ridges to develop and amplify north over the US and Europe. Below is a map showing a typical pattern associate with a positive NAO.

During a negative NAO, a piece of the ridge gets cutoff, and creates a block over Greenland. This makes it easier for arctic air to move south, and over the US and Europe. Below is a map showing a typical pattern associated with a negative NAO.

As you would imagine, a negative NAO greatly increases the odds of east coast snows.

The Arctic Oscillation or the AO

Again when it comes to the Arctic Oscillation you can see by the image above that it has been mainly negative and we are expecting that to continue as well.

Thus far we have a – PDO – GLAAM –AO – NAO + SOI and a QBO going negative based on the –GLAAM.

Pacific North American Oscillation

As you can see via this image for the most part the PNA has been positive but it has its times of fluctuations. We expect no different for the upcoming winter where we will have times of positive and times of negative PNA.

Now lets look at winters that have featured a Negative Nao & Negative AO and Negative ENSO (La Nina)

Based on all the above information and that anticipation of a LA NINA equal to the 2010-2011 ..we have come up with the following maps for the winter of 2011-2012..

Winter 2011-2012 Temperatures

 

Winter 2011-2012 Precipitation Outlook