Message to all observers, 2006 June 7:
Billowing clouds in the NEB

Attached is a set of images showing spot interactions in the NEB in considerable detail.  On May 24 Chris Go pointed out a small, very bright
spot in southern NEB (marked with red arrow), just Nf. a dark NEBs projection (marked with red V).  This bright spot is presumably a convective
plume, possibly a thunderstorm.  The development of this spot is perhaps not spectacular or unusual, but it may be a well-observed example of an
interesting phenomenon. Would you like to look for other possible examples, in your own or other observers' images?

Through the sequence you can see how the NEBs projection drifts faster than the arrowed spot, which in turn drifts faster than NEBn features such as
white spot Z. There is also complex rift activity around white spot Z.

The arrowed spot was visible, but very small, before it passed the NEBs projection; then it suddenly brightened; then it doubled; and then it merged
with the EZn, creating a bright notch in the NEBs edge. I wonder if this behaviour is common: 
1) do other such spots erupt as they pass NEBs projections? 
2) do they commonly merge with the EZn to take the place of white plumes f. the NEBs projections?  
I have never looked systematically, but recall seeing an example in the Voyager imagery (see Figs. 8.2 and 9.2 in my book); and watching the Cassini
movies, I have the impression that behaviour (1) may be common.

Would anyone like to look for other possible examples, in your own or other observers' images from 2006 April and May, and let everyone know what you
find?  This would be a good time to look, as the NEBs projections are becoming quite strong this year, and there have also been other tiny white
spots in southern NEB in your images.  I will not be able to study this further for the next 2 weeks as I am running exams.  Even if you just find a
few images showing candidates, let me know and we could look for other images to complete a series.

After the new white notch formed, it did not drift relative to the dark projection, and it disappeared on June 1.  However it is also of interest to
follow such features because an atmospheric scientist asked me recently if there is any systematic motion of the NEBs white plume cores relative to the
dark projections.  I think there is not, but we might be able to investigate the question in more detail now, when there are plenty of nicely-formed
projection/plume structures in your images.  

Also, recall that NEBs dark projections sometimes get larger or darker (or are disrupted) as they pass NEB rifts.  You could look for such interactions
happening now. 

Also in the attached set of images, note that white spot Z is approaching another anticyclonic white oval (AWO) in NEBn p. it.  (Previously there was
a merged barge p. WSZ, formed by merger in March, but it was destroyed by the rifts as it was overtaken by WSZ in April.)
WSZ has never been seen to merge with another AWO, so let's watch this interaction closely and see what happens!  WSZ is at L2 ~ 220.

The attached image set is at half resolution ? inspect Chris Go's originals for full resolution.  

A final comment on these images, from a parochial English perspective:  Back in the 20th century, we English observers could pretty much take a holiday
(and catch up on reports!) during these southerly oppositions of Jupiter. The reason is obvious when you see the blurry images that even Registax can
produce from here.  But now these fantastic v-hi-res images come from the Philippines, Australia, Brazil, etc...  there is no time for a holiday!
Anyone who can help with analysis is welcome!  However, you can also see that images from Europe, even England, are still worthwhile for following
rapidly changing features because of our longitude: the very last image of that NEBs notch was from England.  

Steady skies,
John Rogers, 2006 June 7


John H. Rogers : Jupiter Section Director,
[British Astronomical Association.]