“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
As I typed on 23 May, I will not be able to do my next discussion until the weekend of 5-7 June. In general, postings will be difficult this summer due to travel, covering shifts, etc.. This is all the more reason why our effort needs to be mainstreamed asap. Please email me/leave comments if you have questions.
Please see links in the 23 May discussion for real-time and other information. An apparently rapid GWO 7-8-1 transition is occurring as I type, and zonal mean westerly wind flow anomalies are strong in the subtropical atmospheres (~plus 5-7m/s at ~15N/250mb). Loosely, a superposition of phase 5 for the MJO and phases 8-1 of the GWO 250mb snr psi composite anomaly plots depicts the current global circulation. I think the wind and convective signals getting back into sync. That coupling is probable to occur in the region of the west Pacific Ocean during the next few weeks, projecting in octants 6-8 of MJO/GWO phase space, which is on the El-Nino side. Having the expected difficulties, most models are starting to capture a USA synoptic evolution days 5-10 fairly consistent with the atmosphere heading toward these GWO/MJO phases.
As the subtropical westerly wind flow anomalies propagate poleward, relative to climatology the North Pacific Ocean jet will strengthen. Perhaps as part of a more robust coupled GWO/MJO 7-8-1 transition, at some point this jet is likely to come into the western states while collapsing, leaving a trough in its wake. This could lead to a very active southwest flow storm track focusing on the central/northern Plains/Upper Mississippi Valley regions ~mid June. Weather impacts, as well as all the issues with unpredictable timing and other details, are understood.
As compared to a year ago, I am now convinced that some form of an El-Nino is more probable going into the 2009-10 boreal cold season. However, the issues raised in past discussions remain valid, and we need to diligently and rigorously monitor. Will the tropical convective forcing signal finally "get out of Dodge (La-Nina)" and start hanging out in the west Pacific beginning this summer? That is, in contrast to the past 2 Northern Hemisphere cold seasons, be displaced toward octants 6-8 of WH (2004) phase space? Stay tuned.