There is little overall change in the spatial pattern of global SSTs since my last discussion. Anomalous horseshoes of warmth and coolness remain across the
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
There are a couple of observations I would like to share. First, per 5-day averaged TAO buoy data, equatorial subsurface anomalies are currently nearly opposite (through 6 June) compared to a year ago. That is, while the equatorial
Continuing, as shown in the SSTA Hovmoller plot per following link,
there has been an approximate biennial character to warm and cold events since 2001-02. For example, note the periodicity of the ~1.5C anomalous warmth in relation to the date line.
However, that behavior appears to have changed since early 2007. Tied to the latest basin wide cooling, the above average warm pool SSTs have shifted to west of 140E on the equator. There are numerous other points that can be raised. Cutting to the chase, based on diagnostic monitoring utilizing various tools, a lot of work involving the coupled ocean-land-atmosphere dynamical system is going to have to be done to shift anomalously warm SSTs into the west central
Full disk satellite imagery shows intense to severe tropical thunderstorm activity extending from the Arabian Sea east-southeast into the extreme west central
Updated through 6 June, WH (2004) phase space plots, particularly with the interannual component left in, indicate a nearly 2 standard deviation MJO projection in phase 3. This coherent evolution of MJO #6 was not captured very well by most statistical and dynamical predictive schemes. There are still predictions of quickly decaying this event, and I do not agree with that. Based on some thoughts of coupled dynamics involving the earth-atmosphere AAM budget, discussion was offered a week-ago that the tropical forcing would remain intact taking on the west-northwest to east southeast orientation across the Eastern Hemisphere discussed above. Those same processes led to a rapid increase of the surface trades (~5-10m/s anomalies) across the central and western
I feel quite comfortable where I think the coupled global weather-climate system is at, and where it may be going. Keeping in mind seasonal cycle issues (boreal summer, austral winter), meridional symmetry of zonally symmetric zonal mean circulation anomalies continues. There is strong tropical-extratropical coupling leading now to a Branstator (2002) circumglobal teleconnection of midlatitude ridges. Some of the details of this situation were discussed last week. Even though the WB (2007, 08) GWO projection may appear weak, updated through 5 June there is still an orbit nearly in phase 3, and the above is consistent with a La-Nina base state. As stated previously, this type of circulation response to dynamical processes involving tropical convective forcing and midlatitude mountains has been observed frequently since January 2008 (“the season of the witch”).
Through 5 June, global relative AAM is ~minus 1 standard deviation below the R1 data climatology, with a near zero tendency. There are also relatively weak global signals of the surface torques and zonal mean AAM transports (for now). Hence why the WB (2007, 08) GWO projection is not that robust. However, the latter is a dynamical measure of the global circulation meaning that is it important to pay attention to its evolution. During the last couple of weeks there has been a clustered positive global mountain torque event peaking around 15 Hadleys just before 1 June. That has contributed to the most recent circuit in the WB (2007, 08) GWO phase space centered on octant 3, and a regional response of another anomalously strong
Animations of upper tropospheric daily mean vector wind anomalies continue to present the expected and improving circulation response consistent with the WB (2007, 08) GWO. Twin upper tropospheric tropical anticyclones are becoming established the
I think the Eastern Hemisphere tropical convective forcing will coherently propagate east, with the centroid perhaps reaching the west central and northwest Pacific Ocean weeks 2-3. Last week I speculated a scenario suggestive of a slow evolution toward an equatorial
Given the history of the last 5 MJOs, keeping in mind seasonal issues including the Indian/Asian monsoon systems, I think it is probable for a component of coupled tropical forcing to shift into the
While uncertainty is always there, I disagree with official forecasts stating there is currently not enough information to make probabilistic risk statements of temperature, precipitation, severe local storms, etc. beyond day 10. Relying on the models alone, not only for subseasonal predictions, but even much shorter time scales, is a cookbook and NOT meteorology (insert angry Rottweiler!). Once the work of the WB (2007, 08) GWO comes to maturity that will include tools such as overlapping statistical composites and an objective predictive scheme for the GWO (with hindcasts, etc.), a much more sophisticated evaluation of the numerical models will be possible.
Slowly shifting northwest with the seasonal cycle, ramifications of western
As discussed above, portions of the
Please see the latest statements from the JTWC and TPC for tropical cyclone concerns. A late season tropical hazard may continue week-1 for the Arabian Sea and Bay of Bengal, shifting 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. In fact, we are close to submitting part-1. 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 will not be able to post another discussion until the weekend of 21-22 June. However, stay tuned for any “quick updates” prior to then.