© 2019 Terry Swails

WINTER IS COMING BACK STRONG....

February 1, 2018

Make no mistake about it, the march is on towards the colder phases of the MJO (Madden Julien Oscillation). I've been patiently waiting for pressures to rise over Australia and the process is underway. Look at surface pressures today over the country. Still relatively low as indicated by the blue and green colors.

Look what happens by the 16th of February. Pressures are higher (yellow) over Australia and points west. This indicates an enhanced convective wave has passed Australia to the east. That indicates the MJO is soon to leave the warm phases its been touring since mid January.

Another way to measure the developing change is by monitoring the SOI (Southern Oscillation Index). When it's positive, especially over plus 10, the convective wave is to the west of Australia forcing a warm MJO phase. Look at the SOI readings since January 15th. Mostly in the range of plus 10 to 25. A maximum of 25.68 January 23rd. Today however the SOI is -0.23 indicating the wave is passing. With rising pressure in Australia, that number should continue to fall and remain negative in coming days (as it was in late December and early January). That ends the dominance of the warm phase.

You can also see the MJO is on board with this trend, as it should be. Follow the green lines below and you can see we head into the cold phases of 1, 2, and 3 by the middle of the month. You can see the February temperature anomalies associated with those phases to the right.

Here's what NCEP has to say in its MJO discussion. Notice the last paragraph.

The U.S. climate model the CFSv2 also sees the cold generating these temperature departures days 0-10:

 

Days 10-20: 

The next 45 days:

With the cold air back in place it certainly enhances the potential for snow in the next week. There's going to be a strong baroclinic boundary cutting through the Midwest that will be a battle zone ripe for storms and snow in the cold sector. I believe some part of the central or southern Midwest within the fight trench could be in line for more than a foot of snow in the next week. That is something I will address in my next post. Until then, roll weather...TS

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