7 May 2002:  Twin vortices/cyclone pairs (response to posting immediately below)

From: Mark Williams <Mark.Williams@bom.gov.au>

Re the tropics.

There are now another pair of vortices which have formed further east, near 100e with very good signatures at 850 and especially 200hPa, though the 200hPa vortices are a bit further east than 100e.  How often do you get one
pair of vortices near the central Indian Ocean followed by another further east a few days later??

Another question, why have we NOT had any northwest cloud bands with such
deep troughs off the WA coast?

John McBride

Hmm... I must be slipping... I missed this one.  I just had a look: the vortex pair at 850 hPa, near 100 E) is hard to see... and is relatively small scale.  The upper tropospheric 200 hPa reflection, however, is a classic; with a clear easterly  stream on the equator and anticyclone twins on either side.  I have put a link to the latest 200 hPa analysis on my web-page.

Time to go home
JMcB

Mark Lander
Date: Wed, 8 May 2002 12:28:07 +1000 (GMT+1000)
From: Mark A. Lander <mlander@uog9.uog.edu>
To: John McBride <jmb@bom.gov.au>
Cc: tropical-storms@tstorms.org, synoptic_discussion@bom.gov.au
Subject: [Tropical-storms] RE: Twins, Rossby waves, MJO in Indian Ocean

Hi John, TC Group,

    The Indian Ocean is really revved up.  A good case of twin cyclones has formed in the western part of the basin,
and an MJO worthy of note is propagating across the basin (see attached Fig).  This is as good as MJO
gets!. Maybe it will be in westPac next week or so, and give us a classic May twin TC formation there
(a la May 1986 -- Lola and Namu).
    Seems like the MJO plows east and sets off a wake of twin TCs as it goes.  Not an original idea,
but have not had time to dig up the refs.

    Best Regards,  Mark Lander

Good to see so many of y'all at the 25th Hurr.

John McBride

The current satellite image in the Indian is a classic, with  an elongated mass of convection on the equator, and the twin vortices to the west.  There is a nice colour image on the Eumetsat page, which I have reproduced on my web-page, under today's discussion.  I have also sketched a little schematic of the configuration, also on my web-page.

colour_image_twin_vortices

cheers
John mcb