Note: It looks to me like the Sagar Kanya never really did make it into Southern Hemisphere air! In their papers, they insist that the ITCZ was to their south (at approximately 5 S) the whole time. So that's where I put it. Judging from some other atmospheric info (satellite images) in their paper, I think 5 S is a reasonable guess. Also, according to the back-trajectories, they were more or less always getting air from the North  though they did say they hit convection at the ITCZ, so it was probably pretty well mixed). Almost all of the trajectories also spent significant time over the ocean (5-10 days), so until they were right up against the coast, they didn't really get much from India. Most of it circled around via the Bay of Bengal (for the plots they published).

The different plots are for:

Baldrige, 1995             (ITCZ = 7 S)
Sagar Kanya, 1996      (5 S)
Ron Brown Leg 1        (2 S)
Ron Brown Leg 2a     (Leg 2 going North ) (4 S-- just a guess here)
Ron Brown Leg 2b     (Leg 2 from far north to farthest south) (11.3 S)
Ron Brown Leg 2c     (Leg 2 return to Male') (ITCZ shifted to 9 S)

In each case, I put the "ITCZ" where I thought the fully Southern Air began. So the zero latitude on this plot is really the southern *edge* of the ITCZ.

The 3-tiered structure is interesting! Obviously the south is pretty much always the same, but then it looks like the second tier is NH background, the third is what we get if we're getting something off the continent, but it was a ways away, and the wild stuff is what we get when it comes to us on the A-train. I guess that makes it 3 tiers plus one special case.