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#460613 - 23/10/2006 20:46 Early Start to Monsoon?
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
Well, there's been a lot of talk about the unusual amount of moisture floating around up north at the moment. With STC Xavier hovering away; a disturbance at 5S 160E that Fiji is keeping an eye on; and now a convection explosion over PNG. What is going on? Is this all part of a developing MT? Probably not, but it's certainly unusual for this time of year. Any thoughts?

I thought I would start this thread to consolidate WA, NT, and Qld discussion on this possible early occurrence.

Here's a sample of a discussion between Raindammit and Seaweed from the TC Xavier thread to get things going:

quote:
--------------------------------------------------------------------------------
Originally posted by seaweed:
Two questions, is this cyclone lying on a developing monsoon trough or is it a standalone system? If it is on a weak MT, is it possible for the decaying system to drag the MT lower for a bout of early wet season rain?
--------------------------------------------------------------------------------

Was thinking the same thing myself seaweed, I don't think its attached to the Monsoon trough as such (correct me if I'm wrong), but the BOM do mention the cyclone being linked to a 'trough' in their high seas forecast:

'Tropical Cyclone Xavier [centre 970hPa] was located near 11.0S167.8E. Forecast
positions are near 11.5S167.1E at 230600UTC and 12.0S166.6E at 231800UTC. Trough
extends from Eq150E to Xavier.'
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#460614 - 24/10/2006 06:22 Re: Early Start to Monsoon?
Pacman Offline
Meteorological Motor Mouth

Registered: 14/11/2001
Posts: 5355
Loc: Cairns - Upper Bentley Park
I think you'll find that it isn't the monsoon trough that is playing its part in the formation of Xavier.
To me it seems Xavier has formed along the rather active SITCZ, which has been unusually active for most of the year now.

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#460615 - 24/10/2006 10:26 Re: Early Start to Monsoon?
E-J Offline
Weather Freak

Registered: 17/04/2006
Posts: 626
Loc: Innisfail (Mourilyan)
Correct me if I am wrong, but doesn't the SITCZ exist between 8S to 2S and 130W to 90W
_________________________
'Building a perpetual motion machine is easy - keeping the thing running is the hard bit"

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#460616 - 24/10/2006 10:41 Re: Early Start to Monsoon?
Rainy Night Offline
Weatherzone Addict

Registered: 01/02/2004
Posts: 4267
Loc: Jindalee, Brisbane
The South Pacific (inter-tropical) convergence zone exists at similar latitudes on our side of the date-line as well (between the Solomon sea and Fiji area). You will find reference to it in the South West Pacific Marine forecast on the Fiji Met site. It has been there for most of this year, but its presence doesn't always indicate an active monsoon. So it is correct to say that a monsoon has not played a part in the formation of Xavier. It may be that tropical cyclone activity in that area could help to induce the monsoon over PNG and areas east of PNG, but perhaps it is too early for that yet.

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#460617 - 24/10/2006 10:41 Re: Early Start to Monsoon?
windjammer Offline
Weather Freak

Registered: 31/08/2006
Posts: 948
Loc: Nowra, NSW
BOM are predicting a renewed phase of MJO within the next week or 2. I'm fairly new to all this, but it seem that as convection increases in the Indian ocean and travels eastwards, it triggers an active monsoon trough. Are we possibly seeing a renewed phase of the MJO a little earlier than predicted?

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#460618 - 24/10/2006 10:49 Re: Early Start to Monsoon?
AussieMark79 Offline
Member

Registered: 30/10/2005
Posts: 451
Loc: Lake Maquarie area, New South ...
MJO
Madden-Julian Oscillation- Tropical rainfall exhibits strong variability on time scales shorter than the seasonal El Niņo-Southern Oscillation (ENSO). These fluctuations in tropical rainfall often go through an entire cycle in 30-60 days, and are referred to as the Madden-Julian Oscillation or intraseasonal oscillations. The intraseasonal oscillations are a naturally occurring component of our coupled ocean-atmosphere system. ...

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#460619 - 24/10/2006 10:52 Re: Early Start to Monsoon?
Rainy Night Offline
Weatherzone Addict

Registered: 01/02/2004
Posts: 4267
Loc: Jindalee, Brisbane
The enhanced convection around the SW Pacific and PNG has evidently been due to something other than the MJO. As at 22 October, the MJO was only in Phase 1.
http://www.apsru.gov.au/mjo/index.asp

The BoM weekly tropical climate note is due to be updated this afternoon, and may shed some further light on this matter.

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#460620 - 27/10/2006 11:07 Re: Early Start to Monsoon?
Raindammit Offline
Weatherzone Moderator

Registered: 14/02/2002
Posts: 13366
Loc: Townsville & Bilyana NQ
MJO is now in phase 2 so it should be in phase 4 by early to mid November. Phases 4 - 7 have the most impact on rainfall in the tropics during the summer months. My guess that this coming MJO will help kickstart storm activity over the tropics, but its the next MJO which will be due by late December which *should* herald the beginning of the wet season proper.
:cheers:

_________________________
Belgian Gardens, Townsville NQ
Bilyana FNQ

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#460621 - 19/11/2006 17:52 Re: Early Start to Monsoon?
Madmax Offline
Member

Registered: 09/11/2006
Posts: 695
Monsoon trough is attached to the low in the coral sea.

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#460622 - 20/11/2006 22:18 Re: Early Start to Monsoon?
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
MJO is now in phase 2 - the second time in a month. (See above) The first time it obviously came a cropper.
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#460623 - 20/11/2006 22:26 Re: Early Start to Monsoon?
windjammer Offline
Weather Freak

Registered: 31/08/2006
Posts: 948
Loc: Nowra, NSW
Isn't that a bit bizzare? I thought MJO periodicity was generally 30 - 40 days.

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#460624 - 20/11/2006 23:06 Re: Early Start to Monsoon?
Rainy Night Offline
Weatherzone Addict

Registered: 01/02/2004
Posts: 4267
Loc: Jindalee, Brisbane
The periodicity of 30-40 days is just an average. The recent MJO events have been quite weak, and it seems that when a weak one runs out of puff before completing its cycle, another one sometimes takes its place rather quickly.

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#460625 - 21/11/2006 21:07 Re: Early Start to Monsoon?
Madmax Offline
Member

Registered: 09/11/2006
Posts: 695
""Convection again increased in the equatorial Indian Ocean on the 8th November and progressed eastwards during last week. Though the progress of this signal is uncertain, it appears that the Maritime Continent and the western Pacific will see enhanced convection resulting from this active MJO within the next one to two weeks or so.

If this progression would see the regime of enhanced convection reach Australian longitudes, it will be too early for the onset of monsoon over Northern Australia.""

Have a look at whats going on 150-180 east 0-10 south, early monsoon already.

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#460626 - 21/11/2006 21:33 Re: Early Start to Monsoon?
windjammer Offline
Weather Freak

Registered: 31/08/2006
Posts: 948
Loc: Nowra, NSW
Yes, but not for Northern Australia. Someone will probably correct me, because I am a rank amateur at this stuff, but I thought warmer SST's over the central pacific produced enhanced convection in this area, but el nino conditions usually supressed monsoonal conditions over the Coral sea, and Northern Australia, in general. Can someone elaborate further?

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#460627 - 23/11/2006 13:35 Re: Early Start to Monsoon?
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
It seems the MJO is almost in Phase three.
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#460628 - 23/11/2006 13:51 Re: Early Start to Monsoon?
eternal rain Offline
Member

Registered: 10/07/2004
Posts: 5685
Loc: the great sydney desert
Quote:
but I thought warmer SST's over the central pacific produced enhanced convection in this area, but el nino conditions usually supressed monsoonal conditions over the Coral sea, and Northern Australia, in general. Can someone elaborate further?
If the central pacific is warmer (elnino), then obviously it will hog all the convection and leave us with higher than average pressure over aust leading to lower convection. If the central pacific was cooler than avg as it is warmer (la nina), and the SSTs around the tropical aust region were in the range of say 28-34C then one would expect a strong, solid and lengthy monsoon. Last decent monsoon was 2001/2002 if i remember correctly.. At the moment were in a strengthening elnino phase and this will mean much lower than average convection over the tropics here and my gut feeling says this years monsoon will be very weak (if it even arrives)..

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#460629 - 23/11/2006 14:09 Re: Early Start to Monsoon?
Rainy Night Offline
Weatherzone Addict

Registered: 01/02/2004
Posts: 4267
Loc: Jindalee, Brisbane
The effect of an el nino on the monsoon in northern Australia is highly variable as shown by records of events in the last 30 years. Generally, the main effect in Australia is less than average spring and early summer rainfall, and the effects are usually more pronounced in central, southern and south-eastern Australia than in the north. The el nino summer of 1997/98 is one example where most of the Northern Territory actually had a wetter than average wet season with prolonged periods of heavy rainfall and the disastrous flooding at places like Katherine. During the same event, much of north Qld also had a wet summer, including the record rainfall and flooding in the Townville area in January 1998. Every event is different in its effects in Australia, and there are often periods of unexpected good rainfall in some areas.

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#460630 - 23/11/2006 14:50 Re: Early Start to Monsoon?
Raindammit Offline
Weatherzone Moderator

Registered: 14/02/2002
Posts: 13366
Loc: Townsville & Bilyana NQ
Statistically, the tropics are not overly affected by El-Nino during the wet season, except for the eastern CYP north from about Innisfail. Even then the deficiencies aren't too bad:

Summer Rainfall during El-Nino:




Contrast this to a La-Nina year where the affect on our rainfall is much more noticable!

Summer Rainfall during La-Nina:

_________________________
Belgian Gardens, Townsville NQ
Bilyana FNQ

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#460631 - 23/11/2006 20:01 Re: Early Start to Monsoon?
alby_14 Offline
Weather Freak

Registered: 23/08/2005
Posts: 311
Loc: Bathurst, NSW
Quote:
Originally posted by Bokkey:
Quote:
Last decent monsoon was 2001/2002 if i remember correctly..
Gday Bokkey, last year was a ripper across most of the tropics. Significant flooding along the Victoria, Adelaide, Katherine and Daly Rivers and various creeks in the Tanami occurred! TC Monica finished it off in style, giving alot of areas an extra top up late in the season.





Cheers

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#460632 - 29/11/2006 07:01 Re: Early Start to Monsoon?
Inclement Weather Offline
Meteorological Motor Mouth

Registered: 07/03/2006
Posts: 5373
Loc: Diamond Valley
MJO is in Phase 4. It's a cause for optimism as the experimental site indicates:

Quote:
[i]n early February 2004 the MJO phase 4 was associated with substantial rains over much of Qld and northern NSW.
But I won't hold my breath.
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