Tuesday, January 6, 2015

January Outlook: Thaw Gives Way to Final Winter Punch

This is the long range January outlook. In this post, we'll discuss the reasoning behind my expectation for a mid-month thaw, then followed by a return to wintry weather to close January and open February.

Paul Roundy
The above image shows a Hovmoller diagram of forecasted Outgoing Longwave Radiation (OLR) anomalies between 7.5 degrees North and 7.5 degrees South latitude, on a global longitude scale. The blue colors indicate negative OLR anomalies, which depict enhanced convection in that latitude slice, at a given longitude alignment. Similarly, yellow colors indicate suppressed tropical convection, also known as positive OLR anomalies. The MJO waves are shown by solid red lines, with more lines indicating a stronger MJO wave. Dashed lines highlight the suppressed phase of an MJO wave.

Taking a look at this chart, we currently see our Madden-Julian Oscillation wave progressing at a somewhat slow rate eastward, now located around 140 degrees East longitude. Using our MJO OLR composite, with blue and yellow colors having the same meaning as shown in the paragraph above, we can confirm that we are currently in a Phase 5 MJO, just about to switch to Phase 6.

Now, as the Hovmoller diagram shows, we expect our wave to push into that Phase 6 mark before it begins dissipating, and a new wave begins forming way off to the west. The dissipation of our current wave and generation of the new wave should happen around January 21st, meaning the current wave will be free to push through into Phase 6 (possibly Phase 7), generally a phase favoring warmer than normal temperatures in the US.

In late January, the other shoe drops.

The new MJO wave looks to form in time for the final week or so of January, pushing east at a slower rate than our ongoing wave. It will form and strengthen at around the 65 degree East longitude line at this date, which correlates to Phase 1 or Phase 2 on our chart directly above.

The chart above shows 500mb geopotential height anomalies during February, in a Phase 2 MJO wave. Notice the pattern encompassing the Central and Eastern US; strong negative height anomalies are present from south-central Canada into the Northeast. The strength of this anomaly tells me it's more than a simple trough. The longwave pattern here says this may be a piece of the tropospheric polar vortex being shunted south into North America due to blocking high pressure east of Greenland. Luckily, the MJO doesn't drive the whole pattern, so it doesn't automatically mean the vortex will be down to visit again. However, it does give an idea of what late January could be like.

As the MJO wave moves further east in February, the pattern will once again turn warm. But for now, late January and early February are looking wintry across the US.

To summarize:

- A warm pattern is likely in the middle of January.
- It is possible a final burst of wintry weather strikes the Central and Eastern US in the final days of January into early February.



Anonymous said...

Is it possible another wave could develop later in February, or the current waves could dissipate at that time, and temper the early spring idea?

Anonymous said...

Weather bell - Joe Bastardi has been putting out the different models of January - March!! Going to be cold !! His words winter is goi g to go on and on!!

Anonymous said...

By final you mean last cold of winter? Thank goodness I can't wait for spring

Unknown said...

GOOD FORECAST matches what I have been saying for 10 + days

DT wxrisk.com

ps BUSTARDI is a fool.. how is that 1976-77 analog woeking out joe ?

Anonymous said...

I to would like to know if you are meaning the last cold for the winter?? Wouldn't that be a "Merry Christmas"!!
Its so cold here now I'm having a hard time staying warm. Doesn't matter if I turn up the heat, when I look outside I instantly freeze! I feel so sorry for all the cows, horses, any live stock that has to endure this cold!
We have a stray cat that hates me but doesn't mind trying to get inside every time I open my glass sliders, poor thing, I do feed it & have made a cozy bed(out of a dog house) with hay (or straw, I cant tell the difference) in it to help keep the thing warm.
Hopefully you meant winter will be short lived Andrew, we wont hold you to it, we know its always changing, just hope this time for the best!

Frank-o said...

October was a very warm month and very wet....Hence,... we have had a very warm and very rain filled winter....I see little change after this 3 day cold snap drys up.....we have had no winter...

Anonymous said...

Frank-o, you can't forget about November, also for me (northern Ohio) temps have been winter like most of the past 10 days though this week has been coldest. December had warmer temperatures in 2011 and 2012. Not convinced the year is a true loss.

Anonymous said...

What it looks like as of now, is that temps will moderate slightly next week, then the possibility of getting into the mid 30s in the great lakes, then late january to early february looks to be cold and potentially very cold and snowy to end an kickoff february.It also looks like if any "mild" spell happens, it will be very brief so only 1-3 days of moderating temps. Beyond that, it is much too hard to tell, and even this is hard to tell right now. So many models shifts have happened this winter, so I'm taking this as a grain of salt because we won't know for sure until we get within a week or less of what's going to happen.