“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion.
The 91-day signal to noise ratio (snr) anomaly composites are again being updated daily. There are still some map room issues that will hopefully be resolved soon. WB (2009; likely not to be published until next year), part-1 of a 2 part paper where the GWO is formally introduced, is in press for MWR publication. There is a link in the Appendix to download the manuscript.
Please remember that these discussions are part of an experimental effort involving linking weather and climate. Until this effort is formalized at the national level, many important scientific issues we are easily well aware of cannot be addressed. Stated another way, it is nearly impossible for me to talk about “everything” in these postings, including offering attribution to unpredictable noise. Plans are moving forward to have a one-day workshop on the WB (2009) GWO concepts during February 2009 in
Like a broken record, the spatial pattern of global SSTs remains entrenched. There is a strong negative phase of the PDO (extratropics have a role) and the central and eastern equatorial
The warmest SSTs globally extend from north of
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
The wind and convective signals are still out of sync (discussed in last 2 postings), and the dynamics as explained by WB (2009) measure of the GWO is “calling the shots”. The MJO signal is weak, in octant 4 of WH (2004) phase space leaving in the interannual component. Additionally, just as the La-Nina like global atmosphere has been forcing much of the tropical oceans for nearly 2 months, the extratropics have been forcing the tropics for at least the past couple of weeks. I can only wish that I could stop writing right here.
Moist tropical convective forcing has been getting better organized in the region of western
The Western Hemisphere enhancement during the last ~2 weeks especially across tropical
Since September, there have been 3 circuits in phase space of the WB (2009) measure of the GWO (recent two ~3 sigma), each succeeding event seemingly making a larger excursion toward “high AAM” having periods of roughly 30 days. The dynamical processes, loosely involving first poleward AAM transport by the eddies (through RWDs; the early October situation most robust) and then “responding” surface torques, have worked to increase global westerly wind flow anomalies. For example, during mid November RWDs from the anomalous upper tropospheric Dateline twin cyclones placed the wicked ridge from Hell along the
As discussed in WB (2009), the GWO is an independent mode of subseasonal atmospheric variability. This boreal autumn may be a “clinic” demonstrating that to the “non-believers”. I think the September and October variations may have been “internal” to the extratropics (got to keep this simple!), while the most recent and on-going event is starting to involve the tropics (recall the above about the convection). Having my reasons, I think the seasonal cycle linked to the southward shift of zonal mean Northern Hemisphere westerlies is partly responsible. The latest evolution from phases 4-5 to 8 in GWO phase space has taken more than 2 weeks, much slower than the past two. The extended jet from
About 10 days ago, global relative AAM was ~2 standard deviations above the R1 data climatology (GWO1), the highest in about 2 years. Updated through 4 December, with minor variations both the global friction and mountain torques were strongly negative. The recent explosive north central
The above paragraph is intended to offer a quick attribution to the large negative AAM tendency (GWO2), ~ 30 Hadleys, that has been expected, observed 4 December (averaging periods understood). Relative AAM is approaching the R1 data climatology. Also, particularly across the Northern Hemisphere AAM is once again fluxing poleward, with the maximum divergence ~40N.
Animations of upper tropospheric daily mean vector wind anomalies show twin tropical anticyclones getting better defined ~120E with downstream cyclones around the Dateline. While details are still complicated that will not be addressed here (ex., a well defined Northern Hemisphere positive phased subtropical wave train (Branstator (2002) is present), our zonally asymmetric wave-1 pattern of tropical circulation anomalies is returning. Phases 4-5 of the WH (2004) MJO snr psi composite anomaly plots reasonably depict tropical circulation anomalies.
I think the GWO signal is coming back into the
The current retrogression of extratropical circulation anomalies across the Asia-North American sector, expected for at least the past 2-3 weeks (see past discussions), is directly tied to what appears to be the wind and convective signals syncing up. The relatively repeatable GWO variations have presented opportunities to offer reasonably successful statements of probabilistic predictions.
Typical during an orbit through phases 7-8-1-2 of GWO phase space, all global numerical models and their ensembles have struggled with their circulation forecasts, in this case capturing the on-going PNA retrogression. For example, about 2 weeks ago nearly all models were predicting the ridge from Hell to persist along the
Models have now generally caught on to what some would describe as a large amplitude reverse/negative phase of the PNA teleconnection by week-2. I think it is probable this situation may persist the rest of this month per above. As discussed in past postings, particularly weeks 2-4 there should be episodes of significant precipitation along the
Whether or not JFM 2009 has similarities to JFM 2008 is unclear. At some point the warm southwest
Internationally, locations focused on western
Please see the latest official tropical cyclone forecasts for all basins. I trust the expertise of the appropriate meteorological centers to alert the public of additional weather hazards worldwide. For instance, there is an intense cold air outbreak currently impacting
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. We hope that an opportunity will arise for us (soon) to allow our dedicated web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcasts.
The WB (2007) paper on the GSDM has been published in the February issue of MWR. The first of a two-part paper, where WB formally introduce the GWO (WB (2009)), has been accepted for publication MWR. A pdf of the in press version can be downloaded from the following link:
In addition to the subseasonal snr composite anomaly plots, we hope near real-time discussions with “weather maps” will become a routine part of the ESRL/PSD GSDM web site sometime soon. Part-2 of our GWO paper will discuss the latter. We want to emphasize notions such as global-zonal mean-regional scale linkages as well as forcing-response-feedback (with subsequent interactions) relationships. An important purpose is to provide a dynamical weather-climate linkage framework to evaluate the numerical models in a sophisticated manner as part of a subseasonal (and any time scale) forecast process, in addition to a climate service for all users. Relying on the numerical models alone is a cookbook! I plan on posting a discussion the weekend of 13-14 December.