THE MJO, IT TOLD ME SO...

June 4, 2020

The Madden Julien Oscillation is a great tool to use when trying to establish trends. By defining areas of convection in the tropical Pacific, it then depicts temperature and precipitation trends based on analogs with similar convective set-ups.

 

What's neat about the MJO is that it often foretells a pattern before the models see it. That's a valuable tool to have as a forecaster. Here's a good example of how the MJO has had me very leery of a prolonged stretch of warm weather the GFS was indicating. Note how the 18Z run on May 29th had highs in the 80s and 90s in the Quad Cities June 2nd through June 14th. 

 

When I see a 13 day stretch of weather without a single high cooler than 80 this time of year, the first thing I do is see if that's in line with the MJO phase analogs for temperatures during that period. On May 27th you can see by way of the dotted green lines the MJO, June 2nd through the 10th was moving through phases 1 and 2.

The phase 1 and 2 temperature analogs are not conducive to widespread warmth around my area and most of the central Midwest. That is a huge red flag and I have been pushing the idea since late last week that while we would get some warm days in the period we are in now, it was not at all likely to be as hot or unbroken as models were showing. Phase 1 and 2 imply troughing over the east that often leads to great lakes highs and back door cool fronts.

If anything, models are leaning even cooler in current runs, especially next week. Now look what the GFS is forecasting.Those 80s and 90s have been replaced with 70s and 60s.

These are its temperature departures days 5-10 (June 8-13)

These are the departures day 10-15 (June 13-18) Wow, what a change. In fact I suspect this is overdone as the ensembles are not as cool, but the point is, the MJO was never on board with the idea of prolonged heat. It saw the way before the deterministic models did. This is why the MJO is an exciting teleconnective tool for seeing or verify trends in our current models.

By the way, the EURO has this for day 10-15 departures. No serious summer heat there.

Something else I mentioned last week in a post was that the MJO phases of 1 and 2 during June have a tendency to produce above normal precipitation over much of the central Midwest. Take a look, green is above normal.

This could again be a signal of heavier precipitation during the time it takes the MJO to swing through phases 1 and 2. One of the reasons this appears quite possible is the remnants of what is likely to be hurricane Cristobal are slated to move into the Midwest early next week. We won't have the big winds but the energy and deep tropical moisture will be drawn into a trough pushing east out of the Rockies. It's too early to say precisely where, but from that set-up alone a swath of 2-4" rains would be possible ahead of the remnant energy. That's not including what might fall in any other events during the overall 2 week period.

 

The EURO EPS ensemble and the CMC take the energy of Cristobal directly towards the Quad Cities next Tuesday. Here is what it looks like on the EURO Tuesday night.

The EURO EPS mean track.

The CMC mean track.

As mentioned, the operational models are starting to trend toward what the MJO was hinting at days ago with generous precipitation totals. These amounts are far from certain but would be concerning for some area rivers and streams which are already high with fairly saturated soils, especially near and east of the Mississippi.

 

The EURO 15 day rainfall forecast

 The GFS 16 day rainfall forecast.

Meantime, Thursday and Friday remain warm and muggy with a least a chance of a shower or storm. These look pretty scattered and some spots may not see them before cooler and much drier air settles in to start the weekend. In fact, Saturday has the makings of a very fine day! That's a wrap. Roll weather...TS

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© 2019 Terry Swails