I want this posting to be shorter. Mature and strong La-Nina SST (and global atmospheric) conditions continue across the
The following are 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)
A loud message to deliver is that the tropical convective forcing has become extremely complex during the past few weeks. I have had to significantly reassess my past interpretations of this forcing. There are multiple areas of intense-severe tropical rainfall causing high-impact weather across the global tropics. Broadly, per full disk satellite imagery, etc., two regions of enhancement can be “lumped together”. One area extends from the equatorial Indian Ocean into the very warm (totals in excess of 30C) South Pacific Ocean (along the SPCZ), with the other from tropical South America into
In addition to the lack of time, it is beyond the scope of what I can present in these discussions the complicated Rossby wave energy dispersions (RWDs) seen during the last few weeks. This is all part of a dynamical system having forcing-response-feedbacks, etc.. An astute meteorologist needs to spend some time monitoring the daily mean evolutions of upper tropospheric vector wind anomalies (just for starters) to gain some understanding for both research and making subseasonal predictions.
For instance, the best defined anomalous twin upper tropospheric tropical anticyclones are over the Western Hemisphere, extending from South America to western
While the WH (2004) phase space plots of the MJO suggest a roughly 2 standard deviation projection in phase 1 (updated through 7 March), this is currently misleading. This is an example where there needs to be a careful understanding of what to interpret, as well as the science behind techniques such as these. In contrast to past discussions when I was expecting MJO #4, there is little, if any, MJO signal in the real atmosphere. The WH (2004) technique is latching on to the upper tropospheric easterly wind flow anomalies across the
I do think it is probable to see the moist tropical convective forcing get better organized across the
Global relative AAM remains very low, ~2.5 standard deviations below the R1 data climatology through 6 March. In addition to the gradual meridional broadening of anomalous zonal mean easterly wind flow anomalies throughout the tropics, contributions have included a persistent negative global frictional torque since early February (~10 Hadleys). There have also been 2 recent episodes of large negative global Coriolis torques of roughly 20 Hadleys spaced 2-3 weeks apart. The negative global frictional torque has come from the midlatitudes of both hemispheres, tied to the storm tracks. During “a typical La-Nina”, the global frictional torque should be, on average, positive due to enhanced trades.
The GWO is strongly in phase 3 (legacy GSDM Stage 1) updated through 6 March. The bottom line is I think it is probable to see roughly 10 day circuits in phase 3 of GWO phase space for at least the next 1-3 weeks. For the
Before getting into any outlooks, I need to also point out recent PNA responses to complex non-linear feedbacks from an intense Kamchatka anticyclone (wind speed anomalies ~40m/s at 250mb at times) during roughly the past couple weeks. The latter is one of those RWD feedbacks (and essentially random processes having little predictability) alluded to above, and this did its part of maintaining a positive East Asian mountain torque. Hence there was a local source of westerly wind flow, and an unexpected extension of the East Asian combined jet across the
Nothing has changed about considerations involving the stratosphere since last week. Please see the following link for details.
Summarizing, there is no clear MJO signal in spite of what the WH (2004) phase space plots suggest. I do think it is probable to see the moist tropical convective forcing get better organized across the
More troughs impacting the western and central
Finally, I 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, tied to our on-going complicated weather-climate situation. I continue to leave it to the expertise of the appropriate weather centers internationally to alert the public of these risks.
Tropical South America into central 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 a short posting next weekend.