This posting must be a bit loose due to upcoming graveyard shift coverage for a couple of nights. In general, there is no change in my tune from the past few postings in spite of what some models and other tools suggest. There continue to be mixed signals involving multiple time/space scales of the global weather-climate situation. In fact, this has been the case since at least February. However, from continuous monitoring of daily mean fields utilizing our GSDM framework, I have some confidence in my probabilistic feelings of what path the ocean-land-atmosphere system is taking.
We have plans of doing a detailed case study of this past winter after our GWO paper is submitted. For example, the strong MJO and other tropical convective variability that occurred is atypical for a strong El-Viejo. The latter did contribute to the observed DJF temperature and precipitation anomalies that would not be expected from La-Nina composites. Examples include the wetness across the Desert Southwest and extreme snowfall experienced for portions of the inter-mountain west as well as the Upper Mississippi Valley. It is beyond the scope of these blog discussions to properly address serious scientific matters.
Yes, I also monitor other tropical ocean basins including any possible extratropical SST feedbacks. That said, mature and strong global atmospheric La-Nina circulation characteristics remain. In fact, there is some evidence of recent strengthening (more said below). SST patterns across the
The following are a few links for additional SST information:
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.wmo.ch/pages/prog/wcp/wcasp/enso_update_latest.html (getting dated, but still useful).
Multiple regions of enhanced tropical convective forcing remain, including South America, Africa, the central equatorial Indian Ocean and even, at times, the very warm
Whether or not there is a MJO is unclear. The WH (2004) 2+ standard deviation projection in phase 2 (through 14 March) is unrepresentative. This is example where careful scientific understanding of just what defines a MJO as well as the tools used to monitor it is a MUST! For instance, much of that 2 + sigma signal has been coming from anomalous upper tropospheric easterly wind flow anomalies (greater than 10m/s) across the Western Hemisphere.
I do think tropical convective forcing is slowly getting better organized across the
Finally, we cannot forget about the very warm west central-South
Global relative AAM is nearly as low as August 2007, roughly 3 AMUs (or approximately 3 standard deviations) below the R1 data climatology through 13 March. In addition to expanding zonal mean strong easterly wind flow anomalies (~10m/s at 200mb) throughout the tropical and subtropical atmospheres, a negative global frictional torque of ~10 Hadleys has been present since early February. The latter has been coming from frictional dissipation of midlatitude westerly wind flow anomalies. As I stated last week, the latter is not typical of a La-Nina. Instead, it is another feedback process that I cannot discuss here.
In any case, another monitoring issue will be if/when these upper tropospheric zonal mean easterly wind flow anomalies start propagating poleward and downward. At some point these easterlies may reach the surface and significantly ramp up (in addition to what is now occurring) the trades (leading to a positive global frictional torque), loosely similar to what happened after August 2007. Should that occur, one can then speculate that negative La-Nina SSTAs may intensify after boreal spring. The point to all this is from a relative AAM viewpoint, the global circulation has become more La-Nina like since early February, and that may feedback to the SSTs.
The GWO has a greater than 2 sigma projection in phase 3 (legacy GSDM Stage 1), and this is meteorologically realistic. Recall that the GWO takes into account non-MJO tropical convective forcing (roughly 80 percent on average, in the real world), in addition to the MJO. Zonal mean flux convergence of AAM transport (~8-12 Hadleys) has been increasing around 40N during the past week while shifting south. Regionally, this has translated to the storm track shifting southward across the lower 48 states, as was expected a week ago. I think the GWO will weakly orbit in phase 3 for at least the next few weeks, enhancing the odds of more western
Please see the following link for details about the stratosphere. As expected, anticyclonic blocking structures in the regions of Kamchatka and the
There is no change to my
More troughs impacting the western and central
Finally, I still continue to have concerns about the dryness intensifying from far southwestern
Still unchanged, per WMO and other information, quite a bit of severe weather internationally continues to occur (ex.,
Severe frontal rainfall across tropical South America should be waning week-1 and
An experimental quasi-phase space plot of the GSDM utilizing time series of normalized global relative AAM time tendency (Y-axis) and normalized global relative AAM anomaly (X-axis) can be found at
We call the behavior of this plot the Global Wind Oscillation (GWO). While the intent of the legacy GSDM is to extend current thinking beyond the MJO, the GWO quantifies variations used to derive the original GSDM in a manner that is “user friendly” analogous to the WH(2004) “convention”. In addition, the GWO plot does not have the ENSO signal removed.
Please see the revised description of the GSDM per above link. Also, I encourage the readers to study the annotated MJO and GWO phase space plots to help relate the global variations explained by those techniques to “weather”.
Links to CPC and PSD ENSO discussions:
http://www.cdc.noaa.gov/people/klaus.wolter/MEI/ (recently updated)
These are probabilistic statements, and work is ongoing to quantify in future posts (for example, risk assessment maps, signal to noise ratio plots and shifts of probability). We hope that an opportunity will arise for us (soon) to have a dedicated web page effort to expedite more objectively, with rigor, thoroughness and verification. The WB (2007) paper on the GSDM has been published in the February issue of MWR. In addition, a paper is in preparation by WB that will formally introduce the GWO. Given shift work and upcoming travel, updates will be difficult. I will try to issue at least short posting around Friday, 21 March.