The MJO

It is time I talk a bit about the Madden-Julian Oscillation or the “MJO” as forecasters like to refer to it.  The Madden-Julian Oscillation is a tropical disturbance that moves clouds, winds, precipitation, and pressure changes eastward around the global tropics about every 30-60 days.  Typically,  in the Northern Hemisphere the late fall, winter, and early spring have the greatest level of MJO activity.

There are phases in the MJO cycle and models predict where the cycle is headed generally 14 days in advance.  Below is the MJO forecast. The numbers 1 through 8 correspond to the 8 phases of the MJO cycle. The red and purple lines are the past, the green line with black dots is the forecast for the future.  The black dots on the green line are days  You literally have to count the dots on the green line because only the past dates are listed (on the purple and red).

Right now we are transitioning from phase 6 into phase 7 (don’t worry I’ll explain the phases in a minute, I have charts!). I mentioned amplitude earlier, anything close to or in that circle means the MJO will have a very little effect on the weather. I labeled that “Null”. The further you go outside the circle the more the MJO effects our weather. I labeled those “Moderate Amplitude” and “High Amplitude”. By counting the dots on the green line you will see we are forecasted to go into a moderate phase 8 around 11/29 and into a moderate phase 1 December 3rd. The red line is the past, you can see that we have been in phases 3,4,5,6 for the last 18 days.MJOGEFS1124

The Phases change depending on what season we are in, so a phase 7 in one month can be completely different than a phase 7 in another month.  As you can see from a temperature perspective phases 8, 1 & 2 are colder and generally stormier phases for us.

MJOTempsNDJ

As I mentioned earlier the forecast shows a move into phase 8 around 11/29, so let’s look at what the model says for 11pm November 29th through 5 am November 30th.

1129

Next let’s look at the corresponding snowfall forecasted through December 8th here is what the GFS has but more importantly why it has it. It has it because of what it is expecting from the MJO. You have to be cautious with 14-day forecasts, but what I am trying to drive home is how and why the patterns are what they are.  All of this is related to pressure increases and decreases in the Indian Ocean which trigger the changes in the MJO. The long-term forecasters I follow are expecting us to spend longer periods of time in phases 8,1,2 of the MJO (the more amplified you are in a phase the longer you stay in it), and shorter periods in the other phases.

GFSsnow.png

As I said 14 days is a long time, but what we see here is the GFS MJO forecast is in sync with its operational forecast. When I have mentioned that EURO is having problems, I am referring to the fact that it is out of sync with itself.

I will start including the MJO forecast in my updates so you can track it with me.

 

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