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#1501158 - 25/06/2019 09:09 Brisbane adjusted seasonal rainfalls.
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
As time is now of essence for me, I am looking into Brisbane seasonal rainfall patterns a bit closer.

I have altered the Brisbane seasonal rainfalls into JAN,FEB,MAR ( most months for tropical influences ), APR,MAY,JUN ( most months for NW cloud bands some of which produce ECL's ), JUL-AUG-SEP ( the 3 normally driest months, occasional ECL's), OCT,NOV,DEC ( main thunderstorm months ).

The graphs represent percentages rainfall against the averages for each 3 month period.

Of course some named weather events do occur outside these adjusted seasons.

I have gone back to 1860, which is when reliable Brisbane records commenced. There were major floods in 1841 and 1844 but no rainfall totals were taken.

The first is the adjusted summer wet season graph.

Note 1893 and 1974 show almost identical figures. 1893 caused more flooding as the rain resulted from 3 TC's in one month, whereas 1974 saw the rain spread over 3 months with one TC.

The summer rains failures in the Federation Drought were more long lasting than the recent Millenium Drought. The last few years in Brisbane ( except 2019 ) has a return to more traditional summer wets, no doubt helped by 3 ex TCs in 2013,2015,2017.

More graphs will be produced soon.

I will then look into 4 monthly totals should time permit ( DEC-MAR, APR-JUL, AUG-NOV )


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#1501159 - 25/06/2019 09:27 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 3505
Loc: Wollongong, NSW, Aus
Great stuff, RWM. I'm hoping that your statement "as time is now of the essence" isn't a reference to some bad news on your behalf? frown

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#1501167 - 25/06/2019 11:25 Re: Brisbane adjusted seasonal rainfalls. [Re: Kino]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Originally Posted By: Kino
Great stuff, RWM. I'm hoping that your statement "as time is now of the essence" isn't a reference to some bad news on your behalf? frown


Thanks Kino. Although aged 70 with neck and feet arthritis, asthma, high blood pressure, double vision ( glasses for this causes dizziness ) - the lot in the middle is OK thankfully.

Other circumstances have caused me to speed up this research.

Graph No.2 should be out after lunch.

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#1501175 - 25/06/2019 12:54 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Brisbane adjusted seasonal rainfall - Apr,May,Jun - the predominant NW cloud band, with some ECL's - months.

Of interest are the constant high totals from the 1860's, and again from the mid 1960's. Once again the Federation Drought totals are generally less than the Millenium drought.



The remaining 2 graphs should be available later today.....

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#1501176 - 25/06/2019 13:00 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 3505
Loc: Wollongong, NSW, Aus
To the naked eye, the period late 1890's til 1930 hasn't been matched since for it's dryness.

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#1501178 - 25/06/2019 15:06 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Blair Trewin Offline
Weatherzone Addict

Registered: 13/07/2001
Posts: 3983
Loc: Melbourne, Australia
Interesting. Which sites did you use? (Often for Brisbane rainfall we use the old Regional Office site and the current AWS, but that has a gap from 1986-1999 for temperature and 1994-1999 for rainfall).

1902 was definitely a standout dry year, although even more so further up the coast; Bundaberg had only about 300mm for the 12 months from December 1901 to November 1902, St. Lawrence less than 100.

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#1501180 - 25/06/2019 15:30 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Blair,

The short Brisbane gap was interpolated and averaged between Greenslopes Hospital, Toowong Bowls Club, Ashgrove Bowls Club, Botanical Gardens. All figures were very close so in interpolation and converted to percentages, the error rate would be small. The new Brisbane site is about 3km from the old one, which itself was moved a couple of times, originally I understand being up near the Windmill.


Edited by retired weather man (25/06/2019 15:35)

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#1501181 - 25/06/2019 15:36 Re: Brisbane adjusted seasonal rainfalls. [Re: Kino]
Knot Offline
Weatherzone Addict

Registered: 01/05/2014
Posts: 2842
Originally Posted By: Kino
Great stuff, RWM. I'm hoping that your statement "as time is now of the essence" isn't a reference to some bad news on your behalf? frown


Ditto.
@RWM you are a scholar and a gentleman
_________________________
Land Ahoy! Ooops!

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#1501183 - 25/06/2019 15:53 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Brisbane adjusted seasonal rainfall - Jul,Aug,Sep - Driest months, again with the occasional ECL. The difference between the two often quoted major drought periods really stands out here.



The final graph in this series available shortly..


Edited by retired weather man (25/06/2019 15:54)

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#1501184 - 25/06/2019 15:54 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 3505
Loc: Wollongong, NSW, Aus
Look at that period 1900 - 1950. Wowsers, so dry.

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#1501185 - 25/06/2019 16:22 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Brisbane adjusted seasonal rainfall - Oct,Nov,Dec - the normal thunderstorm season.

2010 is a standout as it reflects the early start to a big summer wet.

I will now prepare data for a further series of graphs - this time in 4 monthly blocks - Dec,Jan,Feb,Mar...then Apr,May,Jun,Jul,...then Aug,Sep,Oct,Nov. The early 2010/11 wet should really show up in these new summer figures.




However this is where I might have time issues as it takes a long time to get all this together. The graph making is relatively short luckily......


Edited by retired weather man (25/06/2019 16:23)

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#1501187 - 25/06/2019 16:28 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Steve777 Offline
Meteorological Motor Mouth

Registered: 20/10/2011
Posts: 5027
Loc: Artarmon (Sydney North Shore)
Interesting RWM, especially the idea of separating out the different seasons according to their major influence.

There do seem to be several cycles of varying durations operating. The Summer / tropical season (Jan-Mar) seems to have a 40 year cycle, with shorter cycles overlaid. The Winter season seems to have a rough 10 year periodicity.

Maybe there are random / chaotic influences at play.

It would be great if some day it would be possible to predict these cycles, know the drought and flood periods in advance.

P.S. Raining again here in what is proving to be a wet June in Sydney, at least on the coast.


Edited by Steve777 (25/06/2019 16:29)

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#1501190 - 25/06/2019 17:18 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Have commenced adding up the beforementioned 4 monthly blocks.

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#1501202 - 25/06/2019 20:37 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Kino Offline
Weatherzone Addict

Registered: 10/08/2017
Posts: 3505
Loc: Wollongong, NSW, Aus
Clearly been wetter in Brisbane since the 1970ís

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#1501210 - 26/06/2019 01:47 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
amphetamarine Offline
Weather Freak

Registered: 18/03/2004
Posts: 363
Loc: Cairns
Adjusted why?

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#1501222 - 26/06/2019 08:36 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Amphetamarine -

The traditional seasons are Summer ( Dec-Feb ), Autumn ( Mar-May ), Winter ( Jun-Aug ), Spring ( Sep to Nov ). However in the main these traditional periods do not fit in with the weather patterns in Brisbane hence the shifting by one month to do so with the above graphs. Even with this shift there is still some overlap between patterns, hence the reason for the next series of graphs to be in 4 monthly blocks as described above. There will be a delay here as there is a lot of adding up to do over 160 years.

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#1501223 - 26/06/2019 08:42 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
Originally Posted By: retired weather man
Blair,

The short Brisbane gap was interpolated and averaged between Greenslopes Hospital, Toowong Bowls Club, Ashgrove Bowls Club, Botanical Gardens. All figures were very close so in interpolation and converted to percentages, the error rate would be small. The new Brisbane site is about 3km from the old one, which itself was moved a couple of times, originally I understand being up near the Windmill.


Blair, also the new ( current ) site is in a drier location than the previous ones. The previous ones were in the City centre hugging the Spring Hill area. The hill itself causes uplift and so higher falls in certain situations.

The current one in East Brisbane about 3 km away is on flat parkland so little to no uplift. This is certainly evident in the figures I am crunching. I am using percentages based on averages for EACH SITE, not just Brisbane overall, for greater accuracy.

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#1501340 - 28/06/2019 17:17 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
retired weather man Offline
Meteorological Motor Mouth

Registered: 01/07/2007
Posts: 5161
Loc: Wynnum
I now present the final series of graphs into Brisbane rainfall over the past 160 years. These graphs are in 4 monthly blocks.

In perusing both sets it seems that over the 160 years summer rains in general have declined, winter rains in general have increased since 1967, dry season/storm season rains have also tended to increase from about the same time but not as noticeably as the winter rains.

The overall average has remained stable with the balancing I just mentioned. As outlined in the previous post the new Brisbane site is in a drier location than the previous long term ones which may mask averages. This has been borne out in scanning other averages of other " second tier " stations around the City area.

The 4 monthly summer graphs shows a bit of a cyclic nature as well but I will leave that alone here, and let others maybe look into this.

The media have made much of the recent Millenium drought saying "worst ever" etc. Well as far as Brisbane goes the graphs show the Federation Drought was longer lasting with lesser rainfall particularly in relation to summer rains.










If time permits, my next project will be a similar treatment to Townsville rainfall. Its records go back a long way as well. I spent 25 years up there and its location is ideally suited to study monsoonal influences more so than many places north and south of there as these latter locations have orographic assisted totals all year, not seen in the Townsville area. I will work out 2 graphs for Townsville - wet Nov to Apr, and dry May to Oct.

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#1501546 - 02/07/2019 16:12 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
Flowin Offline
Weather Freak

Registered: 15/10/2017
Posts: 966
Loc: Pinjarra Hills, Qld
Originally Posted By: retired weather man
There were major floods in 1841 and 1844 but no rainfall totals were taken.

RWM,
Got this data for 1841 from BoM for station 040214
Statistics Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
year 1841 505.7 82.6 128.5 23.4 134.1 28.7 0.0 5.1 56.1 19.8 123.4 145.0 1252.4

And 1844
Statistics Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
year 1844 278.1 231.6 48.8 80.5 193.0 43.2 69.6 168.7 101.1 127.3 147.3 116.1 1605.3
_________________________
Models are for estimating and gauges are for knowledge.

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#1501553 - 02/07/2019 19:50 Re: Brisbane adjusted seasonal rainfalls. [Re: retired weather man]
amphetamarine Offline
Weather Freak

Registered: 18/03/2004
Posts: 363
Loc: Cairns
Why was Tim Flannery awarded Australian of the year when he said Brisbane dams would never be full again?

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