NOTICE!

The Weatherzone forum has now closed and is in read-only mode until the 1st of November when it will close permanently. We would like to thank everyone who has contributed over the past 18 years.

If you would like to continue the discussion you can follow us on Facebook and Twitter or participate in discussions at AusWeather or Ski.com.au forums.

Page 24 of 53 < 1 2 ... 22 23 24 25 26 ... 52 53 >
Topic Options
#1492782 - 01/03/2019 18:19 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
lurker Offline
Weather Freak

Registered: 21/09/2010
Posts: 86
Loc: Aitkenvale
@Petros - Doesn't really help me. The BOM for the last year has periods of it moving it backwards (west) briefly.

Is the "moving backwards" a recalculation of where the MJO actually is? But if thats so, why would a model incorporate errors into forecasts?

The MJO researcher who used to occasionally post had this to say (2006/2007 thread)

"When the Phase is in or near the centre circle the index is having trouble 'seeing' the MJO.

Thats because the tropics is s busy place for convection, & even though the MJO has distinctive characteristics, it can still be hard to 'pull' out of the background noise.
It pays to be cautious when the MJO pops out of the middle, behind itself. Anti-clockwise, erratic movements indicate somehting else is being picked up laong wih MJO.

Signal strength- ok; that does indicate MJO strength but not the strength of the impact (on rainfall, the monsoon etc)"

I assume Lexi knows more than us about the MJO. So still confused why a forecast model would have anti-clockwise movementts.

Top
#1492787 - 01/03/2019 18:47 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
Lurker, go back to post #.....721 a page back, the MJO tracked westwards only a couple of weeks ago??

Top
#1492789 - 01/03/2019 19:02 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Funkyseefunkydo Offline
Weather Freak

Registered: 30/04/2007
Posts: 906
Loc: East Lake Macquarie
Lurker of the night.🙃

Top
#1492806 - 01/03/2019 22:30 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: lurker]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 3505
Loc: Wollongong, NSW, Aus
Originally Posted By: lurker
@Petros - Doesn't really help me. The BOM for the last year has periods of it moving it backwards (west) briefly.

Is the "moving backwards" a recalculation of where the MJO actually is? But if thats so, why would a model incorporate errors into forecasts?

The MJO researcher who used to occasionally post had this to say (2006/2007 thread)

"When the Phase is in or near the centre circle the index is having trouble 'seeing' the MJO.

Thats because the tropics is s busy place for convection, & even though the MJO has distinctive characteristics, it can still be hard to 'pull' out of the background noise.
It pays to be cautious when the MJO pops out of the middle, behind itself. Anti-clockwise, erratic movements indicate somehting else is being picked up laong wih MJO.

Signal strength- ok; that does indicate MJO strength but not the strength of the impact (on rainfall, the monsoon etc)"

I assume Lexi knows more than us about the MJO. So still confused why a forecast model would have anti-clockwise movementts.



I’m with you for 2 reasons:

- the MJO can’t go backwards as it’s a surge of westerlies, which of course can only head in one direction. What DOES and CAN happen is that the westerlies can ‘pile up’ into tropical systems which is what the model may forecast,
- I still think the MJO forecast is reactive and not predictive which is why it struggles with amplitude such as that forecast clearly has

Top
#1492823 - 02/03/2019 07:28 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3817
Loc: Buderim
BOM defines the MJO as

Quote:
The MJO can be characterized as an eastward moving "pulse" of cloud and rainfall near the equator that typically recurs every 30 to 60 days.


The MJO index measures the location of the strongest cloud and rainfall. The MJO has specific processes associated with it that tend to move the cloud/rainfall pulse to the east. However other processes can and do cause equatorial cloud/rain to move from east to west.

When backwards movement occurs it can be said that the MJO is no longer active. Then once the cloud/rain area moves east again it is the MJO again, and it commences from however far west the area of cloud/rain had moved.

Top
#1492857 - 02/03/2019 12:24 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 19046
Loc: The Beach.
That's right Kino. Eastward only for the MJO.
_________________________


Top
#1492928 - 02/03/2019 22:01 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
lurker Offline
Weather Freak

Registered: 21/09/2010
Posts: 86
Loc: Aitkenvale
@Mike,

Again just asking questions here. Because I am lost.

Some of the definitions talk about a ~5 m/s westward propagating wave. I haven't seen any that say that it stops (or goes backwards). Regardless, the *forecasts* have backward movement, are you saying they are forecasting the loss of signal (or pause?) then a westward movement?

I can understand the human interpretation of the signal having backward movement because a human makes a mistake and thinks some convective activity west of the actual MJO is part of the MJO, only to discover in a few days that that convective activity isn't related; but surely a *forecasting* model would not have human error built into it.

Happy for further discussion as I may be just daft.

Top
#1492935 - 02/03/2019 22:30 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
MOUNTAIN h2o Offline
Weather Freak

Registered: 23/03/2012
Posts: 789
Loc: Hobart Lenah Valley Tas 198 as...
I find it astonishing that all this back and forth verbal tennis match on here leads to no conclusive outcome.
One thing is certain though it's bloody hot .

Top
#1492942 - 03/03/2019 07:58 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ColdFront Offline
Meteorological Motor Mouth

Registered: 29/06/2008
Posts: 19046
Loc: The Beach.
Have a read up on Rossby waves .
_________________________


Top
#1493023 - 03/03/2019 20:09 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
This is a good (MJO sub-conversation), very interested in all comments.

Top
#1493051 - 04/03/2019 09:30 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: lurker]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3817
Loc: Buderim
Originally Posted By: lurker
@Mike,

Again just asking questions here. Because I am lost.

Some of the definitions talk about a ~5 m/s westward propagating wave. I haven't seen any that say that it stops (or goes backwards). Regardless, the *forecasts* have backward movement, are you saying they are forecasting the loss of signal (or pause?) then a westward movement?

I can understand the human interpretation of the signal having backward movement because a human makes a mistake and thinks some convective activity west of the actual MJO is part of the MJO, only to discover in a few days that that convective activity isn't related; but surely a *forecasting* model would not have human error built into it.

Happy for further discussion as I may be just daft.



From my reading on MJO it seems there is not a full understanding yet of what the MJO actually is.

For example, this paper states

Quote:
Despite the widespread importance of the MJO, present-day computer general circulation models (GCMs) typically have poor representations of it (Lin et al. 2006; Kim et al. 2009). Moreover, simple theories for the MJO have also been largely unsuccessful, both in explaining the MJO’s fundamental mechanisms and in reproducing all of its fundamental features together. There have been a large number of theories attempting to explain the MJO through mechanisms such as evaporation–wind feedback (Emanuel 1987; Neelin et al. 1987), boundary layer frictional convergence instability (Wang and Rui 1990), stochastic linearized convection (Salby et al. 1994), radiation instability (Raymond 2001), and the planetary-scale linear response to moving heat sources (Chao 1987). These theories are all at odds with the observational record in various crucial ways (Lau and Waliser 2005; Zhang 2005), and it is therefore likely that none of them captures the fundamental physical mechanisms of the MJO. Nevertheless, they all provide some insight into the mechanisms of the MJO.


The paper is from 2011, so there may be something better out there, but I have not found it so far.

The MJO index does not exactly capture the MJO, but it does measure something quite similar to the MJO. It measures the patterns of wind circulations, and cloudiness, and matches this to the ideal MJO that is most similar. This something does move westward as well as eastward, not just in forecasts, but in observations:



Now either this something captured by the index is an approximation of the true MJO which moves close to where the index is, but never moves backwards. Or the true MJO really does move backwards from time to time. Seeing as we don't seem to fully understand the MJO, I don't think we can say which is true.

Top
#1493054 - 04/03/2019 10:08 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 966
Loc: Pinjarra Hills, Qld
I've had a look at the BoM's archive of 90 day MJO plots over the Jan to Mar period going back a few years. I noticed that in years like 2006, 2013, 2017, 2018, when the MJO position is outside of the centre circle through much of January and February (I take the centre circle as meaning the MJO is weak and not discernible) that the MJO in those years returns to the circle (i.e. is weak) towards the end of March.

The MJO ensemble forecasts across different models are often widespread and often do not show much consensus at all beyond about a week or ten days ahead. But in the current MJO forecasts there appears to be more consensus among the models that a weakening MJO back towards the centre circle is looking likely, and that would be consistent with the previous years I mention above.

Just an observation, I am not an expert on MJO.

Top
#1493055 - 04/03/2019 10:09 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
MJO is looking strong out in central Indian ocean going by the SatIR. Pacific has now returned to a similar easterly trades situation to that of a month back, will cool the Nino3/3.4 regions over the next week I'd think. Nino1.2 has only a veneer of warm water covering a decent cool subsurface profile, I'd expect that zone to cool over the next few days given the fresh SE'lies now established above it.

SOI remain strongly negative.

All adds up to "more of the same" in my book, with one exception: the Quidge is not in place, nor expected to for the next 8 days or so. Hope that helps rain chances for QLD/NSW.

Top
#1493060 - 04/03/2019 11:37 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
lurker Offline
Weather Freak

Registered: 21/09/2010
Posts: 86
Loc: Aitkenvale
So NOAA mentions eastward propagation of the MJO in these slides.

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf

Top
#1493091 - 04/03/2019 18:27 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
The trades are very strong along the Pacific EQ region from the equator Nth to 5degN - will be interesting to see what happens to the Pacific SSL anomaly chart, and SST across Nth Aus into Indonesia over the coming 4-5 days:

Top
#1493092 - 04/03/2019 18:31 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Funkyseefunkydo Offline
Weather Freak

Registered: 30/04/2007
Posts: 906
Loc: East Lake Macquarie
Looks non existent on ascat.

Top
#1493154 - 05/03/2019 08:42 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Mike Hauber Offline
Weatherzone Addict

Registered: 13/07/2007
Posts: 3817
Loc: Buderim
The recent WWB has finished, except for weak westerly anomalies persisting in the east. There continues to be substantial warming in central and east regions and weakening of the warm pool near the dateline.



SST pattern is becoming steadily less modoki like, and central (3.4) and eastern (3) nino indexes are now overtaking the dateline index (4):

nino 4: 0.78
nino 3.4: 0.8
nino 3: 0.92

Westerly anomalies extending into the central and eastern Pacific is much more east based than modoki like. Cloudiness over the longer term is still mostly anchored modoki like to the dateline, however the latest 1 day cloudiness shows substantial anomalies spreading well east of the dateline. One day of course is only 1 day, but it may be the start of a trend towards a more east based cloudiness pattern.



In the subsurface TAO has warmed somewhat, and is now more consistent with the NOAA values.



There is still a window with the MJO in the Indian regions for disruption of the current el nino conditions, but so far nothing significant seems to be coming of this. If we don't see a significant cool Kelvin wave out of this then we would appear to be headed towards the CFS forecast of a steadily building el nino throughout the year, but hopefully more east based which might at least allow an Autumn break of the generally dry conditions.

If we build steadily into a moderate el nino the situation is then like 86/87/88 and 14/15/16 where weak el nino/warm neutral conditions built through the first year into a stronger event in the second. In contrast other back to back el ninos such as 02-05 and 91-95 featured substantial breakdown of warm SST conditions during Autumn.

Rainfall conditions for Autumn in 87 and 15 suggest dry conditions are more likely during Autumn 2nd year of a 2 year event, but its a very small sample.





Edited by Mike Hauber (05/03/2019 08:49)

Top
#1493285 - 06/03/2019 10:19 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
Todays SatIR confirms the MJO now arriving into W Indonesia as most MJO modelling predicted. Clear sky is evident over the Indian Ocean over NW Aus, and the SST chart shows the ocean warming up there (imo partially due to less cool ocean currents heading up past the NW Cape over past week).

MJO models now predict the MJO will be strong over central Indonesia in a couple of days time, then slowly die out without moving eastwards into the Aus region.

The long range models show a tropical storm to develop up near Darwin in 4-6 days time - and I for one reckon they are on the money.

Top
#1493369 - 06/03/2019 22:52 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
ashestoashes Offline
Weather Freak

Registered: 22/10/2017
Posts: 739
Loc: Voyager Point (South West Sydn...
Crikey Would you look at all that PW sitting of the West Coast.


But then knowing our luck atm, I just had to head to the mjo forecast. Basically stopping dead in its tracks before AUS, might come in as Darwin's worst wet season ever.




Edited by ashestoashes (06/03/2019 22:53)

Top
#1493386 - 07/03/2019 08:45 Re: Climate Driver Discussion 2019 (Enso, IOD, PDO ,SAM etc) [Re: ColdFront]
Petros Offline
Meteorological Motor Mouth

Registered: 30/12/2002
Posts: 8071
Loc: Maffra, Central Gippsland, Vi...
If MJO goes Null over Indonesia, there is no mechanism for kill off the PW NW of Aus, esp. if the trades along the Pacific Equator and the region to 5 deg N of it continue to deliver warm water currents into MJO phase 5 zone/130E imo.

Top
Page 24 of 53 < 1 2 ... 22 23 24 25 26 ... 52 53 >


Who's Online
1 registered (1 invisible), 38 Guests and 3 Spiders online.
Key: Admin, Global Mod, Mod
Today's Birthdays
aussie_thunder, Davem29, Joidy, kymm, Pinhead, Steveo1, tramar
Forum Stats
29947 Members
32 Forums
24194 Topics
1529247 Posts

Max Online: 2985 @ 26/01/2019 12:05
Satellite Image