© 2019 Terry Swails

THE REST OF WINTER, WHAT MY CRYSTAL BALL SHOWS....

February 9, 2019

There's some important things happening in the south Pacific and Indian Ocean that are likely to have significant implications on the coming weather in the Midwest. In the graphic below you will notice that over the last 4 weeks surface pressures have been higher in Tahiti than in Darwin, Australia. Compare the column in yellow to the pink on the right.

 

That's an important distinction because its produced a southern oscillation index (SOI) that's been primarily neutral to positive during that period. The 30 day SOI average 0.04

 

What I'm seeing now is a change in that trend as modeling indicates rising pressure in Australia and lowering values in Tahiti. Below is the surface pressure anomalies out 7 days. Note the higher pressures over Australia and the Indian Ocean (in orange) indicating sinking motion. East of Australia in Tahiti pressures have lowered (in blue).

This reversal is underway and the way you can tell is by observing today's SOI value below. It has dropped to (minus) -10.33. 

What this tells me is that the SOI is likely to continue making a very significant decline in the days ahead signaling the MJO (Madden Julien Oscillation) is making its move into the coldest phases of winter. Sure enough the EURO is sensing the transition and is showing the MJO getting more and more amplified as it travels through phase 8 and into phase 1. You can see the progression from now through February 22 by following the green dots on the phase diagram below

Notice how the Midwest is cold in phase 1 during January, February, and March. One thing I would change I would argue for is less cold in the east with the mean trough centered more in the central U.S.

Aside from having temperature ramifications, the big drop in SOI levels will mean an energetic pattern with an active southern jet stream across the U.S. This all leads into my theory that winter is far from over and the coming weeks will be somewhat colder than normal with above average snowfall over much of the central Midwest.

 

To that end the ensembles of the EURO and the GFS are showing a healthy pattern for snow over the Midwest the next 2 weeks. Here's the mean snowfall for the next 15 days on the EURO EPS, comprised of 51 members.

The control run of the EPS is even more bullish.

The mean snowfall on the GEFS (more than 20 members) is just as aggressive as the EURO EPS.

Because the snowfall forecasts you've seen are ensembles, it means some members are further north while others are further south on storm tracks during the forecast period. In other words, you are looking at the mean of all the solutions (51 total on the EURO EPS). It's impossible to say which members will win out in the end, The heaviest snows could shift north or south so keep that in mind. Whatever happens, it's a very good bet that some part of the central Midwest is going to do more than its fair share of shoveling during the final weeks of winter. More on the specifics with each passing storm. Roll weather...TS

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