Oh MJO, Where Do You Go? [6/4]

Overview:

  • MJO Phase 2~3…..??
  • Pacific Zonal Winds Not Favorable for Propogation

Current State of the MJO

Below I have posted an image of the current MJO. Starting at the top image we see 200 hPa anomaly centered over the Indian Ocean, both north and south Indian Oceans are experiencing negative velocity potentials. This is indicative of upward motion (associated with convection), hence the 2nd image also shows MJO superimposed with the negative VP anomalies. The third image, kelvin wave, is another oceanic component associated with MJO. Its the coupling aspect of the MJO wave where the sub-surface/westerly winds are described as a kelvin wave. This helps move subsurface anomalies, which eventually translate to sea surface temperatures and that impacts our ENSO state. We see some build-up be 60-90 E and then again 120 to 150E. This is not unusual with developing MJO waves to have simultaneous Kelvin wave activity in the Indian Ocean and W. Pacific.

Source

OLR Anomalies are significant in the W. IO and equatorial in the E. IO


However…

Getting the MJO to the W. Pac may be an entirely different obstacle.

Here is the latest GEFS forecast for the MJO propogation.

Source

The light green is the mean ensemble forecast with the gray shading showing the range for various ensemble members. And so we see a bit of a nosedive into a weak signal overall with perhaps re-emergence into phase 4 in the 3rd week of June.

CSF projections

Source

The forecast begins at the dark black line centered on June 4th. Similar to the GEFS, the CFS is expecting some weakening of the MJO signal (red ovals) next week with possible reemergence into 160W-180 heading towards the end of June. It is more aggressive with the MJO wave, keeping it pretty strong signal throughout.

Source

The CSF forecast over the next week or so tries to maintain the MJO -OLR and westerly 850mb wind anomalies in the Central IO and extending over New Zealand. Kelvin wave signal we saw above in the W. Pacific starts to propogate eastward and reached the Dateline.

Source

Another look at MJO projections using simply the velocity potentials shows a significantly weakening 200 hPa anomalies as it attempts to enter the W. Pac.


Winds…

Winds between 20N and 0N have been equatorward and easterly over the Dateline and C. Pacific to end May. The easterlies extend well past 100E. Meanwhile in the S. Pacific mid-latitudes it has strong zonal flow. The mid-latitudes in the N. Pacific more meridional, adding wave flux potential into the C. Pacific.

Composite Plot

The last week or so there has been a bit of a disruption to the S. Pacific zonal flow, vectors pointing equatorward around the Dateline. With latest MJO wave departing the E. Pacific, renewed easterly winds along the equator prevail. We still see easterlies at 100E, but if there is an MJO wave that can maintain itself, we can begin to see tropical-extratropical interaction and mid-latitude tropical forcing that will cause a feedback loop into the W. Pacific enhancing westerly flow.

Composite Plot

For now…

Things appear unsettled with regards to the tropics and the MJO. Will it propagate easteward? What about Kelvin wave warming sub-surface as it tracks east? These are things we have to monitor but there is no clear view.

Slightly retracted E. Pac jet stream means at some point a ridge is going to pop up in the E. Pac extending into the SW US. We can also see signs of E. Asian jet coming alive the last week or so. And that we will have to deal with down the road…

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