Saturday, June 27, 2009
Time constraints (and scientific/efficiency considerations) continue dictate for these discussions to be scaled back. The 6 June posting has relevant links, and there is no need to be redundant.
Short and simple, starting in March and “maturing” during April and May, the global ocean-land-atmosphere dynamical system has shifted toward a weak El-Nino base state. The phase space plots depicting the WH (2004) measure of the MJO and WB (2009) measure of the GWO clearly show this. That is, a general displacement toward octants 7-8. The GWO projection has been “weaker” because of complicated issues involving the dynamics of the earth-atmosphere AAM budget including zonal mean contributions. Remember that the WB (2009) GWO is a global dynamical measure of the circulation as opposed to the empirical and equatorially confined WH (2004) MJO.
SST anomalies across the entire equatorial Pacific Ocean basin including the Nino regions are positive, including ~plus 1C and greater east of 160W. Further, the 29C isotherm is well to the east of the Dateline (see TAO and other plots). However, the subsurface anomalies across the west Pacific are not that robust, only ~plus 1-2C down to around 200m. In any case, this basin-wide warming of the Nino SSTs is a response to the global circulation (more said below), and our weak El-Nino is already (and has been) impacting global weather including the USA. Additionally, as discussed previously, the evolution to get to where we are at (in phase space) has been impacting global weather since December 2008 (recall the GWO driven “cheap” MJOs).
My “punch line” for today is that, in general, the global circulation, as part of a complex forcing-response-feedback “loop”, has been leading the SSTs since about boreal autumn 2006 (see previous posts). The latter includes projections on the “beloved” ONI and other measures such as the PDO. I am concerned this is still going on, perhaps working with the seasonal and annual cycles (there are reasons).
Since about mid-May, anomalous zonal mean westerly wind flows have been shifting off the equator into the subtropical and midlatitude atmospheres, with the largest magnitudes across the winter Southern Hemisphere (greater than 10m/s at 200mb). Frictional dissipation due to interactions with tropical forcing (including a recent weak MJO; e.g., WWBs) and midlatitude eddies led to a strong negative global frictional torque by mid-June. Updated through 24 June the there is a clustered negative global mountain torque of roughly minus 20 Hadleys. The point is this is an example of a negative global friction-mountain torque index cycle linked to atmospheric processes including tropical forcing (GWO 8-1). Global relative AAM has decreased to near the R1 data climatology, and tropical convection has become re-established ~10N/90E, good news for the Indian monsoon system. Will this tropical forcing coherently propagate into the west Pacific Ocean during the next few weeks? Stay tuned.
Like the recent behavior of the financial markets, we have seen an “AAM correction”. However, is this simply a subseasonal variation destructively interfering with El-Nino, or is a process beginning that not only could weaken EL-Nino this upcoming boreal autumn, but perhaps bring a La-Nina situation boreal winter 2009-10? The answer is unclear, and careful daily rigorous monitoring is critical. Hopefully at some point the atmosphere and the financial markets will become decoupled!
Animations of upper tropospheric daily mean vector wind fields do show that anomalous subtropical and midlatitude ridges have returned (bearish). Loosely, phases 1-2 of the both the MJO and GWO 250mb psi composite anomaly plots represent the global atmosphere. Responding to the weakening of the North Pacific Ocean jet, the warm ridge in place across the south central and southeastern states last week is retrograding. That behavior is consistent with a brief excursion toward phases 3-5. However, with low confidence, I think another loop in GWO/MJO phase spaces displaced toward octants 7-8-1 is probable during the next 1-3 weeks. As seen from the snr composites, temperature anomalies across the lower 48 states are very sensitive in this region of phase space (as is numerical model predictability skill). My own thought is the intense heat may be focused across the south central states the rest of this summer, with increasing probabilities of northeastward expansions during August. I will try to write a short posting 3 July.
Saturday, June 20, 2009
“The views expressed are those of the author and do not necessarily represent those of the National Weather Service.”
Please see links from the 6 June posting for current information. I am hopeful that time will allow me to present a more formal discussion next weekend, ~27 June. Whatever the case, the subseasonal dog (Rex the Rottweiler) is always watching!
The global ocean-land-atmosphere dynamical system remains tilted toward a weak El-Nino base state. Per WB (2009) measure of the GWO, the latter has particularly been the case since about mid-May. Having a contribution from frictional dissipation (negative global frictional torque) of anomalous zonal mean westerly wind flows propagating poleward into the midlatitude atmospheres, there is an on-going superimposed GWO/MJO 8-1 transition. In WB (2009) GWO and WH (2004) MJO phase spaces, the latter is probable to appear as another relatively minor orbit displaced toward octants 7-8-1. Phases 8-1 of the snr plots nicely depict the current global weather-climate system.
The equatorial Pacific Ocean basin is generally ~plus 0.5-1.0C warmer than normal. One important monitoring issue will be to see how much of an impact the recent strongest west Pacific WWB in roughly 2 years (~10-15m/s anomalies) has upon the thermocline during the next 1-2 months.
One regional scale response has been a convectively active Western Hemisphere, favoring deep tropical moisture transport into the central USA. I think the notion of most models to show retrogression of the trough-ridge-trough pattern across the lower 48 states during the next couple of weeks is reasonable. The latter is consistent with a brief circuit through phases 2-5 of the snr composites. By later week-2 into week-3, there may be a period of ridging around the west coast suggesting a "cool/wet trough" across the central and eventually portions of the eastern states. On average, phases 7-8 of the snr composites may best represent the global atmosphere the rest of boreal summer.
Friday, June 12, 2009
As I typed on 6 June, my next discussion will not be until the weekend of 26-28 June. The global circulation is weakly tilted toward El-Nino; however, there are some mixed signals involving the weather-climate dynamical system. While tropical convective forcing "hangs back" across the region of Indonesia, a superimposed MJO signal is emerging into the Western Hemisphere. Perhaps there will be another loop in WH (2004) phase space during the next few weeks displaced toward octant 7. The WB (2009) measure of the GWO maintains its weak projection, given the recent persistent positive ~1 sigma global AAM anomaly (R1 data climatology) and minimal time tendency. Simply put, analogous to the current financial markets the GWO is moving sideways. Will this continue the remainder of boreal summer 2009?
A mixture of the snr composite anomaly plots for MJO phases 7-8 and GWO phases 8-1 loosely depicts the global atmosphere. With variations, this situation may continue going well into July. Interestingly, anomalous upper tropospheric anticyclones are starting to dominate the Southern Hemisphere subtropical atmosphere (austral winter), arguably bearish. Stay tuned!
Please see links from the 6 June posting for real-time infomation, and email me/post comments if you have questions.
Saturday, June 06, 2009
Please keep in mind the ESRL/PSD GSDM web link, below, while reading this discussion. Also, part-1 of a paper detailing the WB (2009) measure of the GWO has been published in MWR. See Appendix to download a copy.
The following are links for SST details. Loosely, positive SST anomalies dominate all equatorial ocean basins, with magnitudes ~1-2C. The warmest tropical waters are across the west central and northwest Pacific, as well as portions of the central Indian Ocean, where totals are in excess of 30C. The equatorial basin from ~140E to the west coast of South America is slightly warmer than climatology; however, per latest TAO buoy data not continuously greater than plus 0.5C. Roughly plus 1-3C anomalies were observed at depth along the less than normal sloped equatorial Pacific Ocean thermocline.
The causes for the observed warming across the Nino regions since about last March are complicated and subtle, and require additional careful detailed rigorous scientific analysis. In any case, I again remind the readers that ENSO is a global phenomenon involving all tropical ocean basins as part of the coupled ocean-land-atmosphere dynamical system. For instance, an argument could be made for an equatorial Atlantic Ocean basin-wide warm event during the past few months. A similar situation played a significant role during early 2008, perhaps reinforcing the on-going strong La-Nina at that time. During boreal autumn 2006, an exceptionally warm Indian Ocean contributed not only to shutting down El-Nino, but tilting the weather-climate system toward La-Nina.
As discussed below, the weather-climate system is tipping toward El-Nino. However, serious scientific issues are present (most cannot be addressed here), and the “truth may be told” during the upcoming boreal autumn. Maybe we need a “Rottweiler watch”!
http://www.cdc.noaa.gov/forecast1/IndoPacific.frcst.html (note the initial projection)
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html (link 19)
For the time being, the wind and convective signals are generally in sync. Full disk satellite imagery presents a large region of moist tropical forcing centered ~15N/120-140E, extending from about southern India into the west central Pacific Ocean. Contributing to this rainfall has been some re-invigoration of the regional monsoon systems. Various animations and Hovmoller plots show there has been a coherent eastward shift of the tropical forcing with the circulation for about the last couple of weeks. Prior to that a lot of complicated “high frequency stuff” related to the two “stochastically (GWO) driven MJOs” dominated (see past discussions).
Anomalous twin upper tropospheric anticyclones dominate the west Pacific Ocean centered ~140E, and well defined Rossby wave energy dispersions (RWDs) arc from these features into both hemispheres. For example, keeping in mind seasonal issues, anomalous extratropical ridges are currently present in the higher latitudes near the coasts of both Americas. There is reasonable symmetry between the Northern and Southern Hemispheres, including anomalous zonal mean easterly wind flow propagating poleward well into the extratropics (supporting higher latitude ridges) while westerlies shift into the subtropics. In some sense, a negative phase of a Branstator (2002) circumglobal teleconnection of anomalous subtropical and midlatitude cyclones is present, not seen in quite a while.
Through 5 June with/without the interannual component, there is a good 1 sigma projection of the MJO in octant 6 of WH (2004) phase space, after yet another “loop”. Regardless of the details and the large circuit this past April, there has been a decided tendency for the MJO signal to be shifted toward octants 6-8, approximately the El-Nino attractor. Looping and recent weak projections understood, the same can also be said for the WB (2009) measure of the GWO. This is all in sharp contrast to a year ago. A general superposition of MJO phases 6-7 with GWO phases 8-1 of the snr 250mb psi composite anomaly plots represents the global atmosphere. The GWO phases do a much better job of capturing the role of the extratropical response to tropical forcing, in addition to the AAM transport and topographic dynamics.
Updated through 4 June tropospheric global relative AAM is greater than 1 sigma above the R1 data climatology, the highest since last boreal autumn. Putting aside important details (meteorologically and financially), I continue to find it rather intriguing how “close” the trends of the time series for both global AAM and the DJIA are! Unlike hopefully for the financial markets, is this latest “bull run of AAM” done? I suspect this AAM peak is going to be checked by the oncoming GWO 8-1 transition (correction?).
The anomalous subtropical zonal mean westerly wind flows shifting into the midlatitudes per above are coming down to the surface, leading to a negative global frictional torque of ~10 Hadleys. A negative global mountain torque may soon follow. This may/may not contribute to a large negative global AAM tendency (for reasons); however, the notion of a GWO 8-1 evolution is reasonable for the next 1-2 weeks. Per snr composites, the likely synoptic response for the USA is western and central states troughs as part of an active west-southwest flow storm track across the Plains. In fact, working with the MJO, this situation has been expected for at least the past 3 weeks.
More generally, latest animations and other tools suggest to me the interannual component, eastward shifted from the boreal 2008-09 cold season, may be starting to dominate the weather-climate system. That is, going into summer I think the global circulation may (confidence continues low) persist in a situation shown by a superposition of phases 6-7 for both the GWO and MJO snr 250mb psi composite anomaly plots centered on 15 July, while relatively rapid GWO 8-1 “corrections” occur. This is different than what I was writing 1-2 months ago, thinking at that time a weakening La-Nina base state, as opposed to a shift toward an El-Nino, was probable. Again, the jury is still out whether this trend will amplify going into northern winter.
Please see the composites for weather impacts. Generally, during JJA for the lower 48 states, cooler than normal temperatures may focus on the west coast and northern Plains/Upper Mississippi Valley at times while anomalous heat extends from the southern Plains into portions of the Deep South periodically. There may also be episodes of exceptional MCS activity concentrated on the north central into the central Plains states. Notice that our composites also suggest the continuation of an increased risk for low pressure/cyclonic systems in the region of the Gulf of Mexico and Caribbean. This implies that hybrid systems as opposed to true tropical cyclones may become a bigger issue during at least this summer in those areas and adjacent locations.
All presentations from the 24 February 2009 GWO workshop are available via anonymous ftp. If you have not received information on how to retrieve these, let me know. There was excellent attendance at this day-long event, and feedback was strongly positive. We are working VERY HARD to mainstream this effort. The support is very much appreciated!
Links to CPC and PSD ENSO discussions, and a new experimental forecast technique involving a coupled LIM (3rd link below):
The following are links 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 are working on an opportunity to arise for us soon to allow our dedicated GSDM web page effort to mature, expediting objectively and accountability. This web page effort will hopefully include an objective predictive scheme for the GWO with hindcast measures.
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 introduces the GWO (WB (2009)), is now published in the May issue of MWR, and be can be downloaded from the following link:
In addition to the subseasonal snr composite anomaly plots, we would like near real-time discussions with “weather maps” to 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 complete 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, extremely unscientific, and makes Rex the Rottweiler VERY angry! My next complete discussion will not be until the weekend of 26-28 June. Hopefully I will be able to post brief updates in the interim.