Date: Mon, 31 May 2004 14:53:29 +0930
From: Bodo Zeschke

Hi John
Have a look at what is happening over "Dry Season" Darwin at the moment. A mid-level cyclonic circulation, with an "eye" over Darwin ! Probably the residual circulation from the Mesoscale Convective Complex affecting coastal and maritime regions to the north of Darwin overnight. (McCluer Island had 104mm precipitation in the 3 hours before 23Z/30) !
Thence steering to the WSW under the influence of the prevailing mid-level  steering winds.
Regards
Bodo

PS. I have attached a visible sat image showing the circulation and the eye, and a radar image.

Date: Mon, 31 May 2004 18:54:52 +1000
From: Jane ONeill

Dear John,

An apparent interesting circulation crossed the north coast of the NT this morning -
there has been virtually no official comment of its existence, however it had what
appears to be a definite signature of at least a tropical storm, with spiralling
rainbands and a central 'eye area'.  See enclosed radar image...

The system appeared to develop upper divergence and a definite low - mid level
circulation, collapsing after crossing the coast. The event appears to have gone
unnoticed although I would consider it significant so late in the season even though it
apparently was weak.

Clyve Herbert (AUSSKY/ASWA)
(via Jane ONeill)
--------------------------------
Jane ONeill - Melbourne
aussky@iprimus.com.au

Australian Sky & Weather
http://www.australianskynweather.com

Australian Severe Weather Assocn (ASWA)
 

John McBride

Gedday,

These things always happen when you are busy!!!!

There has been an interesting blow-up of convection over Darwin in recent
days with widespread heavy rainfall, and an "eye".

I received a couple of emails alerting me to this from Bodo Zeschke (NT
RO) and Jane ONeill (Australian Severe Weather Association).

I have put their emails up on my internal web-page at
http://gale.ho.bom.gov.au/bm/internal/clfor/jmb/04May31.html

Their emails include some radar images showing the "eye" and Bodo sent
along a visible satellite image.

For completeness on my page I added a few charts from TLAPS: the 850 hPa
anal, the 200 anal, the deep layer mean and the 850-200 shear, all for 12
Z Sunday night.

Looking at the 850 hPa anal, the circulation is associated with a sharp
western   edge to a strong trade eastelrly flow across the top end. The
easterlies were quite strong: 40 kts on eth Darwin sounding through a
deep-ish layer from the surface up to about 700hPa.  There  is also a
weak equatorial Rossby wavev signal with a westerly maximum on
the equator  and a weak northern hemisphere vortex west of the Phillipines
(however you  spell that).  The Matt Wheeler diagnostics have picked up
the westerly  surge as being a Kelvin wave... and Matt is rarely wrong.

 The deep-layer mean chart was so interesting with that very sharp trough
to the west penetrating into the tropics, I have also on my page put up
the sequence of TLAPS IPV at 345K leading up to the event... there was
obviously a cut-off from the shear zone at the edge of the circumpolar
vortex.
 
 

The IPV 345K sequence leading up to the event:

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