GLAAM Can Be Very Important Factor In Winter Pattern Shaping

Few things we want to look for as we get closer to the winter season...

If we take a look at last years mid and late winter turn around we notice some very interesting trends from the GWO, FT and global MT's. 

Last winter's 250mb height pattern from Dec 1 to Jan 15th had a fairly strong belt of positive heights between 60 and 90N with some lower heights over the mid latitudes and a -AO/NAO/PNA pattern. Strongest blocking was focused over siberia/N Europe with GWO/PDO forcing helping drive a -PNA. This was not a very wintry pattern for the east.

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A strong positive momentum transport in NOV/ early DEC meant very warm conditions for most in the east and central CONUS. If we examine the FT chart we notice a transition to negative anomalies between 40 and 60 north in time for the second half of winter with positive momentum transport between 60 and 70 N. This was a major driver that helped the winter turn around to colder along with 2 SSW event's. 

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During the second half of winter and early spring their was a large increase in lower heights over the 30 to 60N area with stronger blocking over western greenland.

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If we take a look at our current Surface torque anomalies we are picking up similar to where we left off last winter with negative anoms near 50N and positive anomalies further North. Overall global Surface torque is positive as well. Lets see how this evolves as we move towards winter. 

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Current H5 pattern has been pumping higher then normal heights over the tropics with a fairly broad hadley cell. With our expected solar drop off in the next few weeks we should see this pattern slowly reverse. 

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