Bear Market Atmosphere

Equatorial SST anomalies from the Indian Ocean into the Pacific loosely exhibit a spatial pattern of cool-warm-cool with the warmth centered on Indonesia. Interestingly this pattern is roughly opposite to that seen during boreal fall 2006 (Indian Ocean dipole matters understood). Anomaly magnitudes are ~1-3C. The horseshoe distribution of warm SSTs into the extratropical North and South Pacific Oceans is as robust as “ever”, while positive SST anomalies continue just west of South America (local El-Nino conditions) and portions of the tropical Atlantic Ocean.

The warmest SSTs globally extend from Indonesia into the Southwest Pacific, with totals ~29-30C. The Indian Ocean is roughly 1-2C degrees cooler. TAO buoy array 5-day averaged data present a strong signal of deep (at least 200m) anomalous SST warmth of roughly 5C west of the equatorial date line while the cool La-Nina anomalies to the east are ~100-150m deep. As discussed before, this tells us that the equatorial Pacific thermocline is steeper than normal, typical of a cold event.

The cool SSTs with La-Nina have warmed respectably during the last several weeks, having anomalies ~1-2C east of the date line and totals ~25-26C. One of many important subseasonal monitoring issues will be to see if these cool SSTs survive the boreal spring portion of the seasonal cycle. There are several forecast tools suggesting this El-Viejo will persist the remainder of 2008 (see IRI link below).

http://iri.columbia.edu/climate/ENSO/currentinfo/technical.html

In any case, we will see what happens. For readers who simply want to know when to “expect” the next severe local storms/tornado outbreak, an analogy to the above is if overnight thunderstorms will survive the morning diurnal minimum.

The following are additional links for SST information.

http://www.pmel.noaa.gov/tao/jsdisplay/

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 18).

Moist tropical convective forcing has propagated east from the Indian Ocean into the region of Indonesia and the South Pacific Ocean Convergence Zone (SPCZ) during the last 2-3 weeks. Recent full disk satellite imagery and the many other plots I look at suggest this forcing is getting a bit more concentrated in the region of 120-140E on the equator. Loosely the enhanced to severe tropical rainfall extends from the southeast Bay of Bengal into the South Pacific Ocean. Strong suppression exists across both the Indian Ocean and the equatorial date line.

There was a MJO component to the eastward shift (#4 for this boreal cold season). The WH (2004) phase space plots caught on to some of the reality of the tropical forcing, and through 28 March indicate a less than 1 sigma projection in phase 6. There was a greater than 1 standard deviation projection onto this index until 26 March. However, I think the MJO signal has become unclear. Furthermore, I am suspicious there may an attempt of air-sea coupling involving the moist tropical convective forcing discussed above. These subseasonal variations involving the tropical forcing working with other dynamical processes (a few discussed below) have been impacting the global weather for the last few months, including the USA. The latter is true regardless of whether or not there has been a MJO, and operational forecast centers need to start understanding this.

The eastward shift of the moist tropical forcing into Indonesia and the Southwest Pacific Ocean interacting with extratropical processes has added decent westerly wind flow to the global atmosphere. This is the largest contribution of such wind flow since late January-early February. Now there is the issue of understanding the complicated dynamics responsible and where that westerly wind flow has been distributed, at least in the zonal mean sense.

In several past discussions I have mentioned the possibility (and reality) of non-linear forcing-response-feedback processes tied to variable tropical convective forcing and higher latitude blocking structures. Rossby wave energy dispersions (RWDs) have linked the tropics and extratropics in at times seemingly simple patterns. However, an astute reader needs to make some effort to monitor daily (and longer averaging periods) mean animations of various wind fields (upper and lower tropospheric) working with the WB (2007) GSDM framework to see these.

RWDs linked to the recent eastward movement of moist tropical forcing contributed to a strong positive global mountain torque event peaking to ~30 Hadleys (ESRL/PSD plots using R1 data/climatology) roughly 26 March. Blocking structures located near Kamchatka and Greenland also contributed by raising MSLPs well above any climatology. Recall that only north-south global mountain massifs can cause these torques. Positive events occur as the earth rotates against anomalously high pressure thus adding momentum (and westerly wind flow) to the atmosphere. The opposite is true for negative mountain torques. Hence the global AAM computed tendency also spiked ~plus 30 Hadleys on 26 March. The latter is why the GWO nearly orbited to phase 5 on 25 March with ~2 sigma projection before collapsing.

There are a lot of other observations that I could share if the proper resources were available. For instance, I think I can argue that the positive global mountain torque event was also related to the recent poleward propagation of zonal mean easterly wind flow anomalies into the subtropical atmospheres. However, to save space, let it be typed that the positive zonal mean AAM tendency (~2 Hadleys) which started on the equator about 2 weeks ago has already shifted into the midlatitude northern hemisphere atmosphere. The RWDs tied to the convection and the positive global mountain torque may be the culprits.

My point to all this confusion is even though there was an “effort” to add westerly wind flow to the global atmosphere, much of it has gone into the midlatitude Northern Hemisphere and Southern Hemisphere equatorial/subtropical atmospheres. This is one reason for the lack of a decent subtropical jet across the southern USA typical of late March. Global AAM still remains low, ~minus 1 sigma, and is probable to decrease again.

Starting roughly 10 March, zonal mean easterly wind flow anomalies propagated off the equator into the subtropical Northern Hemisphere and midlatitude Southern Hemisphere atmospheres. However, for the Northern Hemisphere, through processes involving the dynamics of the baroclinic eddies (with the RWDs) there was an abrupt shift into the higher latitudes which fed back as yet another contribution to the positive global mountain torque discussed above (confused?).

One bottom line is that locations across the USA currently experiencing drought, floods, etc., are not going to see any real change to the patterns responsible for that for at least the next 1-3 weeks. This is another analogy to the global financial markets, where rallies (like those seen during the past couple weeks) do occur in bear markets. Hence the term, “bear market atmosphere”, where there was a "rally" for increasing global westerly wind flow.

Animations of various tropospheric daily mean vector wind total and anomaly fields show a nice baroclinic response to the Eastern Hemisphere tropical forcing with RWDs linking into the extratropics. That includes a great circle arc to the large anomalous upper tropospheric anticyclonic gyre from northeast Asia into the central Pacific Ocean and trough digging into the western USA (wind speed anomalies ~30m/s at 250mb 28 March). The seemingly zonal flow across the CONUS, resulting in a northward displaced storm track for late March, is a regional-scale response to large-scale circulation anomalies. The consolidation of the extratropical ridges (Kamchatka, central Pacific Ocean) was expected per blog discussions at least 2 weeks ago and differed from nearly all week-2 ensemble mean predictions.

Most numerical ensemble prediction schemes loosely maintain the current circulation structure across the PNA sector for at least the next 2 weeks. There will be variations in amplitude and synoptic details are white noise after day 3. The GWO is probable to orbit around phase 3 (legacy GSDM Stage 1) after its recent excursion nearly into phase 5 (GSDM Stage 2).

Persistence of a northward shifted storm track across the USA having more western states troughs progressing into the Plains is probable for at least the next 2-3 weeks. I can argue some variations of this pattern which may occur; however, those are synoptic details. Weather ramifications should be more than apparent by now.

Repeating, this will increase the risk of high impact weather to above climatology centered on the middle of the country. Locations such as the Upper Mississippi Valley hit hard by severe winter weather may not only experience more of it, but also have “spring” delayed. Violent outbreaks of severe local storms including tornadoes may occur from the lower-mid Mississippi Valley into Iowa and the Ohio Valley, along with more flooding. The latter is probable to shift northwest into the northern and central Plains/Upper Mississippi Valley going into May and June.

Drought must be a concern for the Southern and Central High Plains, particularly southwestern Kansas into western Texas. In fact, these conditions may significantly worsen during the next several weeks. Hence there is an increased risk of high fire dangers, dust storms, crop failures and water shortages for these areas. I can even see a situation where this dryness may expand into the western Corn Belt (ex, Iowa) by mid-summer (not to contradict the above).

Severe weather internationally has decreased during the last week. I continue to leave it to the expertise of the appropriate weather centers internationally to alert the public of these risks.

Severe thunderstorms and flooding rainfall are probable for particularly Indonesia into the Philippines weeks 1-3, impacting locations east of Australia and the South Pacific Islands at times. That does include the risk of tropical cyclones. Intense clusters of thunderstorms are also probable to continue across tropical South America at least week-1. The suppressed Indian Ocean may become active by week-3. Concerns for additional tropical cyclones remain across both the North and South Indian Ocean, eventually all shifting north of the equator. Climatologically, the Bay of Bengal has one peak period of tropical cyclones during May.

Appendix

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

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

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.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

The following is a link to information about the stratosphere:

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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 remain very difficult. I may not be able to post another discussion until the weekend of 12-13 April.

Ed Berry

Like the Atmosphere -- Delayed

Lack of time precludes a discussion until next weekend. In summary, there is little change to my thoughts as written 15 March. Tropical convective forcing has become better organized across the Eastern Hemisphere and is currently propagating east. The core of this enhanced rainfall is on the equator at roughly 110E. The tropical circulation is responding with anomalous twin upper tropospheric anticyclones around 60E and downstream cyclones near 150E (baroclinic mode). RWDs tied to this forcing are leading to a discontinuous retrogression of circulation anomalies across the extratropical PNA sector. For example, a large anticyclonic gyre is developing ~45-50N/160E having wind speed anomalies ~30-40m/s at 250mb.

A serious monitoring issue is if there may be ocean-atmosphere coupling to the very warm (with deep positive anomalies) west central-South Pacific Ocean SSTs during the next few weeks once the tropical convective forcing comes out. We are also at the time of year when equatorial east Pacific Ocean SSTs are the warmest climatologically especially west of South America. In fact, equatorial SST totals from ~120W to the date line have warmed to at least 25-27C going along with the recent weakening of the cool anomalies (~minus 1-2C; lowest in the region of the date line per TAO buoy data). Bottom line; stay tuned about the future of El-Viejo.

The tropical forcing and other dynamical processes linked to the extratropics are beginning to add some westerly wind flow to the global atmosphere, with a large contribution coming from the Western Hemisphere upper troposphere across the equatorial Pacific Ocean. Hence there is some poleward propagation of the anomalous zonal mean easterly wind flows into the subtropical atmospheres of both hemispheres. However, global relative AAM is still ~3 standard deviations below the R1 data climatology (through 17 March) as part of a strong projection in GWO phase 3. Whether or not we get a robust orbit to phase 5 of the GWO during the next few weeks is unclear.

In any event, I again need to emphasize that whether or not the tropical forcing discussed above is evolving into MJO #4 is irrelevant. That component, working with other dynamical processes considered within the GSDM framework, will have impacts on the global weather including the USA during the next few weeks.

A modification I think that should be added to the USA outlooks discussed last weekend is a growing concern I have about the storm track becoming displaced somewhat to the north. I have been suggesting some possibility of southward shifts at times due to feedbacks from higher latitude blocking (taking into account what follows below).

However, zonal mean easterly wind flow anomalies propagating off the equator into the subtropics suggest (in this current situation) a significant increase in the probability of anomalously strong mid-latitude ridges. Hence, at least for the next few weeks the greatest impacts from western USA troughs moving into the Plains may become more focused across the northern half of the country. The latter is not good news for locations such as southwest Kansas into west Texas where drought may significantly worsen.

Appendix

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

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

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, and other information:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/


http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/index.primjo.html


http://www.pmel.noaa.gov/tao/jsdisplay/

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 preparation by WB that will formally introduce the GWO. Given shift work and upcoming travel, updates will be difficult. I will try to issue a discussion the weekend of 29-30 March.

Ed Berry

Update from the Midnight Rider

This posting must be a bit loose due to upcoming graveyard shift coverage for a couple of nights. In general, there is no change in my tune from the past few postings in spite of what some models and other tools suggest. There continue to be mixed signals involving multiple time/space scales of the global weather-climate situation. In fact, this has been the case since at least February. However, from continuous monitoring of daily mean fields utilizing our GSDM framework, I have some confidence in my probabilistic feelings of what path the ocean-land-atmosphere system is taking.

We have plans of doing a detailed case study of this past winter after our GWO paper is submitted. For example, the strong MJO and other tropical convective variability that occurred is atypical for a strong El-Viejo. The latter did contribute to the observed DJF temperature and precipitation anomalies that would not be expected from La-Nina composites. Examples include the wetness across the Desert Southwest and extreme snowfall experienced for portions of the inter-mountain west as well as the Upper Mississippi Valley. It is beyond the scope of these blog discussions to properly address serious scientific matters.

Yes, I also monitor other tropical ocean basins including any possible extratropical SST feedbacks. That said, mature and strong global atmospheric La-Nina circulation characteristics remain. In fact, there is some evidence of recent strengthening (more said below). SST patterns across the Indo-Pacific Ocean sector have been undergoing a slow evolution during the past few weeks. The negative SST anomalies along the equatorial Pacific Ocean cold tongue have weakened a bit, with the coldest currently centered on the equatorial date line. The plus 1-3C SST anomaly warming along the coast of South America can be thought of as part of the ENSO cycle working with the seasonal cycle. We are at the time of year when SSTs west of South America are the warmest. The positive anomalies along the west coast of South America are very shallow while the colder anomalies farther west extend to at least 150m deep per TAO buoy array data.

The following are a few links for additional SST information:

http://www.pmel.noaa.gov/tao/jsdisplay/

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 18)

http://www.wmo.ch/pages/prog/wcp/wcasp/enso_update_latest.html (getting dated, but still useful).

Multiple regions of enhanced tropical convective forcing remain, including South America, Africa, the central equatorial Indian Ocean and even, at times, the very warm Southwest Pacific Ocean. Complicated Rossby wave energy dispersions (RWDs) from the extratropics have contributed to this “mess”, which involve non-linear feedback processes from (for example) the East Asian topography. In fact, I can argue that this whole confused situation started during mid/late January when intense-severe tropical convection with MJO #2 persisted in the west central-South Pacific Ocean for roughly a couple of weeks. The point is there are always these complicated forcing-response-feedbacks, etc. involving tropical and extratropical nonlinear dynamical processes. Looking for “cookbook” ideas such as circulation impacts from a SSW supposedly leading to a negative phase of the AO/NAO do not cut it with me. Life in the real atmosphere is much more complicated than that, and very important to understand if predictions of extreme weather events (for example) are to improve.

Whether or not there is a MJO is unclear. The WH (2004) 2+ standard deviation projection in phase 2 (through 14 March) is unrepresentative. This is example where careful scientific understanding of just what defines a MJO as well as the tools used to monitor it is a MUST! For instance, much of that 2 + sigma signal has been coming from anomalous upper tropospheric easterly wind flow anomalies (greater than 10m/s) across the Western Hemisphere.

I do think tropical convective forcing is slowly getting better organized across the Eastern Hemisphere centered ~0/80E. Full disk satellite imagery and other tricks I use support this notion. Animations of upper tropospheric daily mean vector wind anomalies show twin tropical anticyclones becoming established ~90E with downstream cyclones around the date line. RWDs into and out of the tropics are linked with these features, and are already impacting the USA as I type. Only monitoring will tell if this Indian Ocean forcing begins to shift east during the next few weeks. I suspect it will given increasingly warm SSTs north of Australia (totals ~29-30C).

Finally, we cannot forget about the very warm west central-South Pacific Ocean SSTs, which will shift north with the seasonal cycle. Again, only monitoring will tell if our “nemesis of the new world atmosphere” returns. In any case, international predictions of the MJO in WH (2004) phase space need to be used with extreme caution until further notice. The latter have wanted to predict “loops” in roughly phases 1-3 for the past couple of weeks, which is meteorologically unrealistic.

Global relative AAM is nearly as low as August 2007, roughly 3 AMUs (or approximately 3 standard deviations) below the R1 data climatology through 13 March. In addition to expanding zonal mean strong easterly wind flow anomalies (~10m/s at 200mb) throughout the tropical and subtropical atmospheres, a negative global frictional torque of ~10 Hadleys has been present since early February. The latter has been coming from frictional dissipation of midlatitude westerly wind flow anomalies. As I stated last week, the latter is not typical of a La-Nina. Instead, it is another feedback process that I cannot discuss here.

In any case, another monitoring issue will be if/when these upper tropospheric zonal mean easterly wind flow anomalies start propagating poleward and downward. At some point these easterlies may reach the surface and significantly ramp up (in addition to what is now occurring) the trades (leading to a positive global frictional torque), loosely similar to what happened after August 2007. Should that occur, one can then speculate that negative La-Nina SSTAs may intensify after boreal spring. The point to all this is from a relative AAM viewpoint, the global circulation has become more La-Nina like since early February, and that may feedback to the SSTs.

The GWO has a greater than 2 sigma projection in phase 3 (legacy GSDM Stage 1), and this is meteorologically realistic. Recall that the GWO takes into account non-MJO tropical convective forcing (roughly 80 percent on average, in the real world), in addition to the MJO. Zonal mean flux convergence of AAM transport (~8-12 Hadleys) has been increasing around 40N during the past week while shifting south. Regionally, this has translated to the storm track shifting southward across the lower 48 states, as was expected a week ago. I think the GWO will weakly orbit in phase 3 for at least the next few weeks, enhancing the odds of more western USA troughs in a southward shifted storm track.

Please see the following link for details about the stratosphere. As expected, anticyclonic blocking structures in the regions of Kamchatka and the North Atlantic have done their part to shift zonal mean anomalous westerlies southward. In fact, a weak zonal mean AAM sink has recently appeared ~50N. Again, these blocking patterns and their feedbacks cannot be understood from oversimplified associations.

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

There is no change to my USA outlooks from a week ago. Some models and even a couple of official forecasts have suggested a patter shift of sorts by week-2 meaning an eastern USA trough and western states ridge. That forecast solution is unlikely. Recent numerical ensemble predictions schemes such as the Canadian and NCEP GFS are starting to catch-up to what is proposed below.

More troughs impacting the western and central USA, probable for GWO phase 3, appear likely at least weeks 1-3. I think these storms will periodically impact the west coast. Blocking structures that are also likely to remain/occur at the higher latitudes may shift a southwest flow storm track across the Plains southward at times. This will increase the risk of high impact weather to above climatology centered on the middle of the country. Locations such as the Upper Mississippi Valley hit hard by severe winter weather may not only experience more of it, but also have “spring” delayed. Violent outbreaks of severe local storms including tornadoes may occur from the lower Mississippi Valley into Ohio Valley and portions of the Deep South. The latter is probable to shift northwest into the northern and central Plains/Upper Mississippi Valley going into May and June.

Finally, I still continue to have concerns about the dryness intensifying from far southwestern Kansas into western Texas. There are reasons tied to this base state where storm systems may remain too progressive at least for the next few weeks such that these locations get “dry intrusions”. Hence there is an increased risk of high fire dangers and dust storms for these areas. However, a southward shifted storm track and eventually the seasonal cycle may mitigate that.

Still unchanged, per WMO and other information, quite a bit of severe weather internationally continues to occur (ex., Europe early last week), 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.

Severe frontal rainfall across tropical South America should be waning week-1 and South Africa by the end of week-2. Much of the equatorial Indian Ocean is probable to see enhanced rainfall week-1 then extending into Indonesia as well as Northern Australia and the Philippines by weeks 2-3, latter possibly sooner. Locations east of Australia into the South Pacific islands are likely to remain at least climatologically convectively active until further notice. Finally, concerns for additional tropical cyclones remain across the South Indian Ocean, eventually shifting north of the equator (and eastward) during the next few weeks. Climatologically, the Bay of Bengal has one peak period of tropical cyclones during May.

Appendix

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

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

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.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

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 short posting around Friday, 21 March.

Ed Berry

Witch's Brew Update

I want this posting to be shorter. Mature and strong La-Nina SST (and global atmospheric) conditions continue across the Indo-Pacific Ocean sector. The plus 1-3C SST anomaly warming along the coast of South America can be thought of as part of the ENSO cycle working with the seasonal cycle.

The following are links for additional SST information.

http://www.pmel.noaa.gov/tao/jsdisplay/

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 18)

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 Africa. The latter has led to a significant enhancement of the Atlantic Ocean ITCZ this past week.

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 Africa. While zonal mean anomalous easterly wind flow anomalies dominate the tropical and subtropical atmospheres, much of that contribution is coming from the Western Hemisphere. Considering a very weak pair of anomalous anticyclones tied to the Eastern Hemisphere tropical forcing, there has been a broad zonal wave number 2 pattern of tropical circulation anomalies during the last week to 10 days.

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 Atlantic Ocean too strongly. Hence statistical and numerical predictions of the MJO based on the WH (2004) methodology need to be used with care.

I do think it is probable to see the moist tropical convective forcing get better organized across the Eastern Hemisphere during the next few weeks. This region may cover much of the equatorial Indian Ocean through Indonesia into the Southwest Pacific Ocean. I would also not dismiss the option of 2 regions of tropical convective forcing, roughly the Indian Ocean to Indonesia with a separate region over the Southwest Pacific Ocean. The latter region has the warmest SSTs globally, and I have called this issue our “nemesis as part of the new world atmosphere” in past postings. In any event, whether or not we get MJO #4 is unclear.

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 USA, that shifts the odds toward more western USA troughs (discussed below).

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 Pacific Ocean happened this past week. Rossby wave energy dispersing downstream from this jet led to a strong west coast ridge and the baroclinic storm development currently impacting the eastern USA. This evolution has delayed the shift toward western USA troughs by 1-2 weeks per my 23 February discussion. Someone could then comeback and say, “it is always delayed!” The North Pacific Ocean jet stream is collapsing.

Nothing has changed about considerations involving the stratosphere since last week. Please see the following link for details.

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

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 Eastern Hemisphere during the next few weeks, possibly enhancing La-Nina. Of course, we need to keep in mind ALL issues tied to seasonal transition to boreal spring. The GWO is probable to orbit in phase 3 for at least the next 1-3 weeks. Hence, even though I missed the strong North Pacific Ocean jet this past week, I can almost linearly move up the outlooks from last week up one week.

More troughs impacting the western and central USA, probable for GWO phase 3, appear likely weeks 2-3. Most numerical ensemble prediction systems have been capturing this possibility during the last few days. Blocking structures that are also likely to occur at the higher latitudes may shift a southwest flow storm track across the Plains southward at times. This will increase the risk of high impact weather to above climatology centered on the middle of the country. Locations such as the Upper Mississippi Valley hit hard by severe winter weather may not only experience more of it, but also have “spring” delayed. Violent outbreaks of severe local storms including tornadoes may occur from the lower Mississippi Valley into Ohio Valley and portions of the Deep South. The latter is probable to shift northwest into the northern and central Plains/Upper Mississippi Valley going into May and June.

Finally, I continue to have concerns about the dryness intensifying from far southwestern Kansas into western Texas. There are reasons tied to this base state where storm systems may remain too progressive at least for the next few weeks such that these locations get “dry intrusions”. Hence there is an increased risk of high fire dangers and dust storms for these areas. However, a southward shifted storm track and eventually the seasonal cycle may mitigate that.

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 South Africa have an increased risk of severe frontal thunderstorms/flooding rainfall week-1 and possibly week-2. Much of the equatorial Indian Ocean into Indonesia as well as Northern Australia and the Philippines are likely not done with enhanced rainfall. In fact, I think this situation may again worsen weeks 2-3. Locations east of Australia into the South Pacific Ocean islands are likely to remain convectively active at least weeks 1-2. Finally, concerns for additional tropical cyclones remain from the South Indian Ocean into the Southwest Pacific Ocean. That risk may shift north of the equator during the next few weeks.

Appendix

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

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

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.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

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.

Ed Berry

Global Relative AAM and Financial Markets in Sync

The weather-climate situation has generally evolved as expected per my discussion a week ago and I would like to avoid repetition for brevity. The purpose of this writing is simply an update.

Mature La-Nina conditions continue across the Indo-Pacific Ocean sector and this El-Viejo is not going anywhere anytime soon (warming SSTs west of South America understood). Warmest SSTs globally are still across the South Pacific Ocean having totals ~29-30C, a bit cooler than a week ago due to intense thunderstorm activity along the SPCZ. SST totals across much of the Indian Ocean are ~28-29C. We are getting to the time of the year when SSTs are climatologically the warmest across the equatorial Pacific Ocean meaning 5-day averaged (TAO buoy data) negative anomaly magnitudes ~1-3C (totals ~24-27C) are significant. The equatorial Pacific Ocean thermocline remains anomalously steep, and our latest oceanic Kelvin wave appears to be fading due to increased trades.

The following are links for additional SST information:

http://www.pmel.noaa.gov/tao/jsdisplay/

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 18)

http://www.wmo.ch/pages/prog/wcp/wcasp/enso_update_latest.html (getting dated).

The tropical convective forcing continues to slowly organize across the Eastern Hemisphere, loosely centered ~ 0/100E per full disk satellite imagery and all the other tools I can list. Enhanced tropical rainfall is also present across portions of tropical South America and Africa. I think the early developmental stages of MJO #4 are in progress. Per WH (2004) methodology there is little MJO projection.

Various predictions of the MJO in WH (2004) phase space from worldwide weather centers suggest a strong signal to emerge in roughly the central Indian Ocean (phase 2) by week-2. Having my own reasons, I agree with this notion; however, I think the MJO signal will be farther east by week-2 in the region of the East Indian Ocean to Indonesia (phases 3-4). Persistence of tropical forcing from the west central-South Pacific Ocean of the magnitude seen during January is now looking less probable (at least until MJO #4 comes out).

The global circulation has been responding to the tropical forcing as well as to other dynamical processes explained by the GWO. Animations of upper tropospheric daily mean vector wind anomalies show twin tropical/subtropical anticyclones centered ~110E becoming better defined with cyclones just east of the date line.

The most dominate subseasonal atmospheric signal is currently the GWO (in contrast to the weak MJO), strongly in phase 2 updated through 28 February (more said below). Processes that define the GWO (which includes the MJO) such as AAM transports and surface torques is why recently most Rossby wave energy dispersions (RWDs) have been zonally oriented. With the retraction of the East Asian jet during the past week (tied to the Eastern Hemisphere tropical forcing), there has still been Rossby wave energy dispersed (rather than trapped) along poleward directed ray paths across both the North and South Pacific Oceans. The Northern Hemisphere RWD links up to the trough currently digging across the western USA (1 March). Most operational models have been “playing catch-up” to this synoptic event, trending slower and deeper for the last several days. Hence yet another example of the linkage of weather and climate, and why numerical models cannot be used as a stand alone forecast tool without consideration of the global circulation even for the first few days of week-1.

Global relative AAM is a good 2 AMUs (roughly 2 standard deviations) below the R1 data climatology updated through 28 February. This is the lowest since early December 2007 and already demonstrates that tropical forcing including what is likely to be MJO #4 is amplifying La-Nina. Global relative AAM during the past 12 months was lowest on about mid August, dipping close to 4 AMUs below the R1 data climatology. Interesting that last August was also the month that the global financial markets started having their problems, which still continue. The global AAM tendency is still ~minus 20 Hadleys with components such as the earth AAM tendency and frictional torque contributing. The latter is roughly minus 15 Hadleys mostly from surface frictional dissipation of midlatitude westerly wind flow anomalies that I can easily link to the MJO tropical variability.

The global mountain torque is slightly negative; however, the East Asian component remains slightly positive. The East Asian mountain torque has been generally positive since mid January, providing a local source of midlatitude westerly wind flow for features such as the East Asian/North Pacific Ocean jet. There have been roughly 10-20 day variations of this torque, and I can offer some attribution for it. The point is this local source of westerly wind flow may have been keeping the position of the PNA midlatitude ridge, on average, closer to the North American west coast since then.

Zonal mean easterly wind flow anomalies strongly dominate the subtropical atmospheres, with magnitudes still ~10-15m/s at 200mb for the Northern Hemisphere. Following the zonal mean AAM tendency, after an extended period of Northern Hemisphere equatorward propagation, the anomalous easterlies are again shifting off the equator. Anomalous zonal mean westerly wind flow is present across the midlatitudes. Particularly for the Northern Hemisphere, consistent with this meridional symmetry there is decent zonal mean signal of poleward AAM transport ~30-35N given a subtropical sink and a midlatitude source.

The GWO is arguably the strongest in phase 2 (of phase space) since early December 2007. During the next few weeks as MJO #4 starts to propagate east toward the west central Pacific Ocean, working with other processes westerly wind flow is probable to be added to the subtropical atmospheres. Thus I remain unchanged about my prediction for the GWO to orbit through at least phases 3-5 (legacy WB (2007) GSDM Stages 1-2) which may really “anger” La-Nina.

Yes, there has been a recent major warming in the Northern Hemisphere polar stratosphere. Including the at least 3 minor warmings before that, I can link these events to MJO and other forms of complex variability. Zonal mean 100mb full field vertical EP fluxes are now downward meaning impacts from this warming are impacting the upper troposphere. In fact, in the region of 75N zonal mean easterly wind flow anomalies at 50mb are ~20-30m/s while at 200mb ~10m/s. An astute reader will also observe a zonal mean AAM sink ~60-70N. This all suggests an increased probability of higher latitude blocking along with anomalously high mean sea level pressures for the next few weeks. Carrying on, that can lead to a southward shifted midlatitude storm track.

Climatologically, it is not all that unusual to see the troposphere respond to the stratosphere as discussed above going into boreal spring. In fact, per zonal mean sections of 50mb wind the final stratospheric warming usually occurs by the end of April. Whether or not we are seeing this event early or whatever is unclear. This is nothing more than a dynamical feedback to slow processes including subseasonal atmospheric variations which can be monitored within the GSDM framework. Perhaps this line of thought also adds to the many other reasons why several locations across the USA have March climatologically as their snowiest month. Please see the following link for additional stratosphere details.

http://ds.data.jma.go.jp/tcc/tcc/products/clisys/index.html

Summarizing, another atypical subseasonal enhancement of La-Nina is probable during the next few weeks. Both the GWO and MJO may be approximately in the same phases. Most, if not all, week-2 ensemble means from international weather centers of say, 500mb geopotential height anomalies, give a prediction of a western North American ridge-eastern trough. While I do know where that is coming from, those predictions are misleading since they are weekly means. It would “surprise me” not to see another onslaught of western USA troughs by the end of week-2 continuing at least into week-3 (timing is white noise; usual disclaimer). The following outlook is essentially a repeat from a week ago.

Probable weather impacts for the USA ~later week-2 into at least week-3 with more western states troughs should be easily apparent by now. Weeks 4-5 may see an eastward shift of this regime linked to GWO phases 5-7. This may literally be “the season of the witch! (recall La-Nina means little girl; El-Viejo means anti-Christ, etc.).” Already stated above, higher latitude blocking may shift the storm track a bit south at times. Locations such as the Upper Mississippi Valley hit hard by severe winter weather may not only experience more of it, but also have “spring” delayed. The track of what may be violent outbreaks of severe local storms is probable to shift northwest into the northern and central Plains/Upper Mississippi Valley going into May and June.

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.

Locations from the eastern Indian Ocean through Indonesia, northern Australia and the Philippines are probable to get hammered with intense-severe thunderstorms/flooding rainfall for at least the next 1-3 weeks. That does include a tropical cyclone risk south of the equator. A slow eastward shift is probable as MJO #4 emerges. Hopefully eastern Brasil and portions of central and south Africa will see less intense thunderstorm activity after week-1. At least for the next week or so, the paradise islands of the South Pacific Ocean are not “out of the woods” for episodes of intense/severe frontal thunderstorm activity.

Appendix

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

http://www.cdc.noaa.gov/map/clim/gsdm.shtml

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.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

http://www.cdc.noaa.gov/people/klaus.wolter/MEI/

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.

Ed Berry