This la nina is just about a lock to be a hybrid event.....which means its likely to have mixed characteristics of east and west based la ninas....you can see on the model simulations, the residual anomalies decay slowest between about 120 and 150* longitude....hallmark of a basin-wide, hybrid deal.
This is entirely consistent with my blog-musings earlier this summer (July) regarding the ongoing subsurface dynamics.
State of Subsurface Implies Continuation of Basin Wide Event
Currently la nina remains in a basin wide state, with the strongest anomalies focused west-central region of 3.4.
Back in June, la nina appeared rather stagnant given that the subsurface cold pool was rather meager, save for the extreme eastern region of 1.2.
This is important because the Walker Cycle dictates that line nina is fueled up the upwelling of cooler subsurface water to the surface by easterly trade winds.
Note that throughout July and August, region 4 and the western half of region 3.4 to approximately 140 degrees longitude have been engulfed by easterly trade winds (denoted by blue in the graphic below), which is forecast to continue through the duration of August.
This is important because simultaneously the subsurface cold pool has been intensifying and tracking westward, thorough most or region 3.4.
Thus the most likely area for continued cooling over the next one to two weeks is the central portion of 3.4, at the nexus of the subsurface cold pool and easterly trades. Further to the east, across regions 3 and 1.2, the easterly trades have yet to penetrate, thus there is no mechanism to upwell the cooler subsurface. And across the western flank, within region 4, there exists subsurface warmth. However, the surfacing of positive anomalies is not imminent given the considerable depth at which they are present beneath region 3.4. Thus expectation for the foreseeable future is that this event will continue to remain basin-wide with a central focus on region 3.4.
This maintenance of a basin-wide appeal with a central focus is supported by most guidance at present:
NCEP:
EURO:
CMC: