Gedday,

 Yesterday morning's GOES-West image showed a lovely example of the ITCZ having rolled up into a series of vortices across the eastern Pacific.  The picture immediately makes one think of Guinn and Schubert 1993 mechanism that we have discussed before on this list.  I have reproduced the satellite image on my web-page (under synoptic discussion - today's date)

The image a day later (this morning: 00UTC 24 October) is even more startling.  On my webpage I have placed the GMS image and the GOES-west images for this morning side by side:  the line of discrete vortices has extended westward such that it now incorporates the pre-existing vortex just off the coast of India, has "caused?" a new vortex in the South China sea and has produced a number of incipient vortex blobs around 140 and 160 E.  It is actually fantastic.  For completeness I have placed a sequence of  three days of GASP western-hemisphere low-level analyses on my web-page. The shading is vorticity, with yellow being cyclonic in the Northen Hemisphere.  There is clearly either a data problem or a resolution problem in that the latest analysis does not represent the final-current vortices.  Despite that, from the beginning of the sequence you can see the Guinn-Schubert style east-west extending line of concentrated vorticity in a stretched-tightened mode of ITCZ.  I have also put up a sequence for the last few days of TLAPS 900 hPa vorticicty analyses to show the new spin-ups that formed in the South China sea and the western Pacific.

We are in severe shock here at the moment with the trauma of 100 Australian dead from the Bali bombing, a multiple shooting at Monash University in the suburbs of Melbourne two days ago and my 18 year old son sitting in a tutorial a couple of rooms away on the same floor,the news at night tells us of the Washington sniper..and so on.......

But that old  atmosphere keeps on rolling though..... and still manages to thrill me, at least....

cheers
John McB
 
 

This morning's GMS and GOES west, showing the spun-up "ballsy" ITCZ extending all the way across the Pacific at 10N.

 

The sequence of western hemisphere analyses:

The Western Pacific TLAPS 900 hPa vorticity sequence:

Chris Fogarty
Interesting ITCZ structures in the Pacific, John.   When I look at that satellite image I think of tropical waves in the Atlantic basin.  In the Pacific basin, are these waves or troughs referred to as "vortex roll-ups" instead?  I've been hearing alot of different terminology from other folks studying the Pacific basin...and imagery that looks very similar to features we see in the Atlantic.  I wonder how many features are similar (perhaps the same) with different names...to state the obvious: typhoons versus hurricanes.  Actually, I would like to see a tropical-met glossary for the Pacific basin - can anyone suggest a good one?

One of these "roll-ups" seems to have spawned powerful Kenna off Mexico. One other associated with Lowell (?) and another is under investigation as a possible TD.

Chris
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Chris Fogarty
Research Meteorologist
Dalhouse University / Maritimes Weather Center
Halifax, Nova Scotia

John McBride
Chris,

I agree completely.... The research and operational communities in Australia and the West Pacific look at the GMS satellite image and the local charts every day, and over the years we build up a body of knowledge, some of which is written down, but much of which is passed on to one another as "corporate memory".

What is going on in the Atlantic,over Africa etc is a complete mystery to us.

Hopefully as this sort of email discussion and posting of JPegs continues, we can better see the similarities and differences between the various tropical cyclone basisn. If anyone wants to discuss day by day synoptics of the Atlantic ITCZ, pointing out features in the satellite images and the analyses, please, please, please do so....

As for the "vortex rollups" terminology. That is not standard... It is thinking aloud as we describe what we see... Hopefully a terminology will evolve.

John McB

Chris Fogarty

I was quite startled by the swift organization of Kenna (E. Pacific).

Think about it...the storm went from minimal TS 35 kts (1003 mb) to CAT 5
Hurricane (915 mb) in 48 hours.  That's a mean deepening rate of 1.8 mb/hr
judging by recon missions.  Between 15Z and 18Z on the 24th, the rate of
deepening was 24mb/3 hours - 8mb/hr - yikes!  Also there was a 24-hr pressure
fall of 65 mb between 23/21Z and 24/21Z (see below).  Does anyone have quick
access to deepening rate statistics or extremes to compare with Kenna?  I'd
certainly be interested in seeing them.

I did some crude web-searching and found that Opal (1995 - Atlantic) had 3mb/hr
deepening rate but nowhere near 8mb/hr!  Mitch in 1998 deepened by 54 mb over 24
hours.

KENNA 2002:
8   14.50 -107.50 10/23/21Z   75   980 HURRICANE-1
9   15.30 -108.30 10/24/03Z   85   973 HURRICANE-2
10  15.90 -108.50 10/24/09Z  100   962 HURRICANE-3
10A 16.40 -108.70 10/24/12Z  115   955 HURRICANE-4
11  16.90 -108.70 10/24/15Z  120   945 HURRICANE-4
11A 17.30 -108.80 10/24/18Z  130   921 HURRICANE-4
12  17.80 -108.70 10/24/21Z  140   915 HURRICANE-5

Chris

From: Jim Kossin
Hi John. The standard terminology references the "roll-up of a vortex
sheet". This is also called "vortex sheet rollup" which is sometimes
shortened to "vortex roll-up" although I think that this latter phrase
is misleading. It's generally a 2D concept and the terminaolgy is widely
used in the GFD literature. It is also applicable to any dynamically
unstable strip or annulus, not just sheets.
Best,
Jim Kossin

>
> As for the "vortex rollups" terminology. That is not standard... It is
> thinking aloud as we describe what we see... Hopefully a terminology will
> evolve.
>
> John McB