Global tropical SSTs remain well above average from the East Pacific into the Atlantic Oceans with anomalies ~1-3C and totals near 30C south of
Latest 5-day averaged TAO buoy data continues to indicate expanding subsurface warmth (~plus 3C) down to ~200m west of the date line to west of
The following are links to global SST and related information.
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
Full disk satellite imagery and other diagnostic monitoring tools show there has been a significant increase of intense-severe clusters of thunderstorms from the equatorial Arabian Sea and Indian Ocean east-northeast into Southeast Asia (3-day OLRA ~minus 50-70 W/m**2). Enhanced tropical rainfall persists across northern South America and particularly equatorial
Updated through 30 May, the latest WH (2004) phase space plot shows a much weaker MJO projection, barely above 1 sigma, than a week ago, in octant 1 (with and without the interannual component). Should this be interpreted as a decaying MJO? There are literally an endless number of responses I could offer to that question. However, the point is we have an important evolution of tropical convective forcing and associated circulation anomalies shifting from the Western into the Eastern Hemispheres.
Continuing on the above, strong tropical-extratropical coupling continues (recall last week’s discussion of events since mid April). As was observed earlier this year, once again there is a well defined inter-hemispheric meridional symmetry of zonally symmetric zonal mean circulation anomalies. However, there are some subtle differences (a few discussed below) involving the exchange of momentum between the solid earth and free atmosphere. The WB (2007, 08) GWO, which captures the global dynamical AAM processes including any MJO contribution, has orbited in phase space to nearly octant 3. Without further confusing the reader, another point is that the global circulation, at least for now, is returning to a La-Nina base state.
Updated through 29 May, global relative AAM has dipped to ~minus 1.5 AMUs below the R1 data climatology, with its tendency ~minus 5-10 Hadleys. While the global integral of the surface torques (and tendency) may not appear that large (~0 for the torques), that is anything but true for specific latitude bands of zonal mean frictional and mountain torques as well as the AAM transports.
This above is another example where I feel rather comfortable knowing “how we got here”, but have an extremely difficult time sharing that. It is only a simple matter for me to go back through numerous animations of many fields, daily averaged and longer periods, linking those observations to WB (2007, 07) GWO variations and be able to offer scientifically defensible null hypotheses.
Most broadly, the symmetry I am writing about involves anomalous zonal mean westerlies ~60-70N and S, as well as 30-35 N and S. Anomalous easterlies are present in the upper midlatitudes and the tropical and subtropical atmospheres. Hence the zonal mean frictional torque anomaly is ~plus 2 Hadleys near 45S and ~plus 1 Hadley around 50N. The latter is significant since this is opposite to what was seen during roughly February, and represents one of those subtle base state changes I am discussing. Obviously the overall gradual increase in global relative AAM since roughly early March in addition to the dynamical processes leading to MJO #5 are another example of slow base state changes.
Summing up, there has been a tendency for the WB (2007, 08) GWO to slowly shift away from La-Nina since mid March. Please keep in mind that while I type “La-Nina”, “El-Veijo”, or whatever, this is only a component of a complex global (ocean-land-atmosphere) interannual signal I am really talking about (to not have a “failure to communicate”). Remembering that, subseasonal events constructively and destructively interfering with this basic global circulation state (which are “unusual for La-Nina” – see past postings) have led to the barrage of anomalous western
Okay, so where do we go from here? Zonal mean flux convergence of AAM transport (greater than 12 Hadleys) has maximized ~40N with sinks to the north and south. A similar process is occurring in the Southern Hemisphere. The dynamics tied to the tilts of midlatitude eddies interacting with the surface torques and the tropical forcing are at least partly responsible. Regional-scale responses have included a robust extension of the Australian jet (austral winter) and soon the jet across
Animations of upper tropospheric daily mean vector wind anomalies continue to present the expected circulation responses consistent with the WB (2007, 08) GWO. Twin upper tropospheric tropical anticyclones are becoming established (coming back) in Africa and the western
My feelings are for the tropical convective forcing to become better established from roughly the Indian Ocean into the
The WB (2007, 08) GWO may not only orbit to phase 5 during the next 1-3 weeks, but even drift toward the “El-Nino side”. The WH (2004) MJO phase plot may also do a similar behavior. Focusing now on the
As discussed above, portions of India/Indonesia into Southeast Asia/China may be impacted by intense to severe thunderstorms during the next few weeks. During weeks 3-4 that area of enhanced rainfall may become focused from Southeast Asia into the
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
This phase plot is being re-done, as is the web site. Stay tuned. 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:
The following is a link to information about the stratosphere and other nice monitoring tools:
The following is a link to NCEP model verifications (surf around for lots more).
The following is a link discussing recent global weather and related events.
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 two-part paper is in ACTIVE preparation by WB that will formally introduce the GWO along with subseasonal composites for variables such as surface temperatures. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships.
Given shift work and travel, updates are extremely difficult. I should be able to post another discussion the weekend of 7-8 June.