I have been on travel this past week meaning this posting will be not as complete. Hopefully I will be able to post a better discussion around Tuesday next week.
Per full disk satellite imagery and monitoring tools, I think a renewed moist phase of the MJO is evolving from South Africa into the South Indian Ocean. The possibility of this development was offered in my January 30th posting based on the scientific principles utilized to derive our GSDM, including responses from the rapid weakening of warm ENSO.
The centroid of this convection was at ~10S/60E and extended east to about western Indonesia. Other sporadic tropical convection continued across the South Pacific and South America. SSTs are about plus 1C (at least 29C) over much of the South Indian Ocean and these warm waters will contribute to a lot of CAPE to our developing MJO. I suspect this MJO will become more robust ~90-110E by late week 2/early week 3.
The global circulation is already responding with features such as twin upper tropospheric subtropical anticyclones ~60E and downstream twin cyclones. In fact, the cyclone just north of India tied to this MJO contributed to a recent extended period of extreme cold/wet weather in that region. Upper tropospheric easterly wind anomalies are increasing throughout the tropical and subtropical atmospheres and the tendency of global relative atmospheric angular momentum is about minus 15 Hadleys. The latter is still decreasing with a contribution coming from a strong negative frictional torque (~15 Hadleys) that began about 2 weeks ago. I think we are in Stage 4 of the GSDM and it is probable we will go into Stage 1 during the next 2-3 weeks. There will also remain periodic forcing from the South Pacific that may enhance a climatologically strong subtropical jet.
My feelings about particularly the western and central portions of the USA going into an active pattern for the next few weeks remain unchanged. In fact, I think this regime may mature going into March. We should several troughs first impact the west coast and then move east-northeast across the Plains (loosely). The western states will cool while the east warms. Arctic air may initially build up across Alaska (due to blocking west of the state) and then come into the western/central states during early March. March 2007 may be exceptionally active (above climatology) with (for example) heavy rain/severe storms across the Deep South into the east while late winter/early spring blizzards pound much of the Rockies into the Plains/Upper Mississippi Valley.
Please note: These are probabilistic statements, which we will try to quantify in future posts. My next 1 month period at ESRL/PSD with the HMT project will be from 3/4-4/3. The WB (2007) paper on the GSDM has been published in this month’s issue of MWR.