My apologies for letting this occasional series lapse over recent months.

 As always there are a number of interesting things happening. The relevant charts and figures are on my web-page at http://www.bom.gov.au/bmrc/clfor/cfstaff/jmb/monsoon_list.html
 

Beginning with the seasonal OLR, the time-longitude sections for the season show that over 60-90 E the monsoon this year was marked by one major active event during June-July, with a number of other minor events, including a  recent one during the past week.

Time-latitude section of OLR from 60-90E from the NOAA CDC website: http://www.cdc.noaa.gov/map/clim/olr.shtml

Looking at the time-latitude for a wider section 60-120E shows that in the east of the domain (90-120) there was a second major outbreak of convection during mid-August and that this eastern domain has also had active convection extending from 5S to 15 N over the past week.

The flow over the Indian Ocean has been interesting.  Looking at a time longitude  section (or Hovmoller) for 850 hPa zonal wind at the equator, there has been a localised maximum of westerly wind between about 60-80E since 27 September.  This low level westerly "jet" is somehow related to the retreat of the monsoon as can be seen on the 850 hPa chart for 1200 UTC 29 September reproduced on my web-page.  The westerly current is on the equator at 70 E but extends northeastward across Indochina and the Philippines with positive relative vorticity (yellow shading) on the northern side and negative relative vorticity (blue) on the southern side.  The vorticity bands of either sign have localised maxima.  The one at about 5S 60 E became a very early in the season southern hemisphere tropical cyclone, and and on the northern side, it has given rise to a meso-alpha scale warm cyclonic vortex over India.  Given the scale and structure of this system over India, I would have called it a monsoon depression... perhaps our Indian colleagues can talk to this system.

Another chart for five days later is also shown on my web page. On that one the vortex over India is very well formed, as is the elongated zone of negative vorticity to the south.  It has some of the characteristics of  an n=1 equatorially-trapped Rossby wave, with its twin vortex pairs.  This can be seen on some of the daily Indian ocean EUMETSAT images.  For example the image for 3 October 1330 UTC shows a twin at about 10N and South, 70 E, with a hint of a second downstream twin at 5 N-S,  90E.   The series of images for 5th 1330, 6th 0100, 6th 1330 show a vortex pair at about 10 N-S 80-90E, with the northern member of the twin displaced to the west and the southern member displaced to the east.   The wind structure has a lot of differences from the classical Rossby wave structure, particularly in its north east to southwest orientation, but the satellite signature looks so familiar, I feel there must be some Rossby-wave dynamics hidden in there somewhere. 

Another interesting aspect of the charts is that easterly flow has set in over the northern part of the south China Sea.  I did some work with scientists from the Vietnam Hydrometeorological Service some year ago.  At that time I learned the wet season for the central Vietnam coast (i.e the hump at about 12.5 N on the map of IndoChina) actually has its peak in October with a rapid increase in rainfall occurring through late September to mid October.  It has never been clear to me whether this is associated with rainfall from tropical cyclones or with the onset north easterly monsoon and the effect of elevation as the moisture laden easterlies hit this coastline.  Perhaps our Vietnamese colleagues can talk to this, using the past month as an example?

Some related meteorology is about to occur over India, as  I believe that south eastern India and Sri Lanka experience their main wet season in October- November when the north-easterlies set in.  Could someone from India or Sri Lanka speak to this?

I also would like to show some upper level charts; but its 6.30 pm  and have to go home.  I'll talk about the upper level flow tomorrow. Though herewith a link to one chart for last night, this time the shading being absolute vorticity.  Features include the anticyclone over the western pacific, the cross-equatorial return flow at about 80E, the pockets of cyclonic absolute vorticity located over the major convectve outbreaks.