Gedday,

There are some interesting things happening in the eastern hemisphere tropics at the moment:

The n=1 Rossby wave I was discussing a few days ago off the African coast seems to have spawned tropical cyclone Atang from the southern member of its twin vortices. On my web page I have put up this morning's  Eumetsat image and the concurrent 850 hPa GASP analysis. You can see from comparison of satellite signature of Atang and the twin vortices on the analysis a pretty strong indication this is what has happened... especially if you track back to my earlier message first showing the existence of this vortex pair.  Interestingly the northern member of the pair seems to be  devoid of cloud and  the vortex itself has come-an-gone a bit over the past few days.

Looking further at the picture and analysis there seems to be a cyclonic spin-up off the east coast of India.  I observed something similar several weeks ago... these Bay of Bengal cyclones just seem to suddenly appear without warning as a localised spin-up in the long east-west line of cyclonc vorticity at the southern extent of the northern hemisphere trades.

Another interesting feature today is the SPCZ.  Looking at the analysis, you can see a line of southern hemisphere cyclonic vorticity (blue-cloured) extending from New Guinea  (10S, 150E) to about 20S 170E.  This is clearly the SPCZ, as can be seen from the convection along it on the current GMS image (also on my web-page).

As I have discussed before, I/we often see  a monsoon-trough style ITCZ consisting of an east-west line of -partialU/partial-y vorticity associated with a sharp equatorward edge to an east-west extending band of strong easterly trade-winds.  Well today we have something similar with the SPCZ:   There is a broad band of southeaterly trades in the Coral Sea (off the coast of Queensland) and the vorticity-feature constituting the SPCZ marks a sharp north-eastern edge to this band of trades.
Interesting

John McB

copyright 2002 EUMETSAT