Update: Rogue “MJO Wave”, then “La-Nina Reloaded”

“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.

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

The 91-day signal to noise ratio (snr) anomaly composites are being updated daily. There are still map room issues that are being worked on. WB (2009), 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.

The formal announcement for the 24 February 2009 one-day (~9am-5pm MST) workshop on the WB (2009) GWO has been released through various mailing lists. It can also be obtained from the GSDM web page per above link. Please remember the intended audience of this workshop is forecasters who make daily subseasonal predictions. It will not be a “head banger’s academic ball”. The workshop is open all interested; private, government, etc..

This posting is significantly abbreviated due to upcoming travel. In fact, I would like that to be a trend, particularly if a real-time web page with "maps and figures", as a component of the GSDM site, can evolve.

Global SSTs remain relatively steady state, as would be expected since their anomalies are generally slowly evolving. Slight warming has been occurring across the convectively suppressed South Indian Ocean, while a downwelling Kelvin wave continues its slow propagation into the Western Hemisphere equatorial Pacific Ocean. The latter, forced by weakened trades and actual surface westerlies, is ~150m deep having anomalies roughly plus 2-3C per latest 5-day averaged TAO buoy data. Subsequent impacts, if any, are unclear.

http://www.wmo.int/pages/prog/wcp/wcasp/enso_update_latest.html

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

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.cdc.noaa.gov/map/images/sst/sst.long.time.gif

A much stronger than expected MJO signal is propagating through the Western Hemisphere, located in octant 7 of WH (2004) phase space with and without the interannual retained. For this case, the ~2.5 sigma projection without ENSO is realistic (there are reasons). Satellite imagery and other tools suggest the MJO dynamical signal is centered on the Americas, with an eastward propagation phase speed of ~20-25m/s. These do progress significantly faster across the Western Hemisphere. I expect the MJO to easily re-emerge into the Indian Ocean during week-2.

While arguably unpredictable with appreciable lead-time, I am not surprised by this “rogue MJO”, and I do think scientifically defensible attribution can be offered (perhaps as one of the cases for the GWO workshop). In fact, concerns of this possibility including weather impacts were expressed in discussions last (boreal) fall. The gist is red noise dynamical processes captured by the WB (2009) measure of the GWO, working with the annual cycle, likely forced the coherent eastward propagating convective signal (south of the equator) projecting on a MJO.

The circulation response has included subtropical transition of upper tropospheric anomalous anticyclones (cyclones) to cyclones (anticyclones) across the Indian Ocean (west Pacific Ocean), and extension the East Asian jet (EAJ) forcing a large positive phase (shifted west) of the Pacific North American teleconnection (PNA). Phases 6-7 of the MJO 250mb snr psi composite anomaly plots depict the global tropical and even extratropical circulation. The recent severe USA cold Arctic outbreak that focused on the northern and central Plains-Northeast is directly linked to all the above.

The GWO (R1 data AAM plots updated through 15 January) has shown little variation and projection since early this month, shifted slightly toward La-Nina in phase space, suggestive of the on-going interannual component. However, just as the MJO destructively perturbed La-Nina, rapid constructive interference is very likely the next 1-3 weeks as it's signal returns to the Eastern Hemisphere. The surface torques are collectively becoming negative contributing to an already ~minus 20-30 Hadley AAM tendency. A sink-source zonal mean AAM poleward transport signal has also appeared across the subtropical and midlatitude atmospheres of the Northern Hemisphere. Hence the GWO has spiked into octant 1 of phase space. I do think a relatively synchronized GWO/MJO 7-8-1 transition is starting, and all that should lead to a global circulation depicted by phases 2-3 of the 250mb snr psi composite anomaly plots. As is typical during these types of regime transitions (on our list to quantify), all global numerical weather prediction models have been struggling badly the last several days.

The long awaited PNA discontinuous retrogression will start week-1, responding to lingering Indonesian tropical forcing. The “western trough/southeast ridge pattern” should mature by ~ week-3 as Eastern Hemisphere tropical forcing intensifies, having USA weather ramifications similar to December 2008. Monitoring will tell if this situation “locks in”. Remember that while also stronger than expected, the 2008-09 La-Nina encore is still “pale” by comparison to a year ago (as is typical). In any case, keeping in mind climatology, I do have some concern of one or two significant/severe baroclinic winter storm developments focusing on the Plains roughly weeks 2-3. There should also be concerns that at least portions of the Plains during the next several months may have weather ramifications similar to late winter-spring 2008.

Intense to severe tropical thunderstorm activity is probable to shift from South America and South Africa week-1 into the equatorial/South Indian Ocean week-2 (a large change). The focus should be from the Indian Ocean into Australia and Indonesia by week-3. The lingering convection currently centered on Indonesia is a response to the La-Nina global circulation base state.

I trust the expertise of the appropriate meteorological agencies to alert the public of additional weather hazards worldwide, including official statements for tropical cyclones that are likely to impact regions such Madagascar week-1. Locations farther east including northern Australia will have an increased tropical cyclone risk weeks 2-4. Portions of particularly Western Europe may have several rounds of intense/severe wind and rain during the next couple of weeks.

Appendix

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 and other nice monitoring tools:

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

The following is a link to NCEP model verifications (surf around for lots more)

http://www.cpc.ncep.noaa.gov/schemm/z500ac_wk2_na.html .

The following is a link discussing recent global weather and related events:

http://www.wmo.ch/pages/mediacentre/news/index_en.html

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:

http://www.cdc.noaa.gov/map/clim/wb08_revised_final.pdf

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 at least an abbreviated discussion on ~24 January 2009.

Ed Berry