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#893482 - 25/10/2010 15:38 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
There may be some climatological significance in rain falling on or near the 28th of January. I know for a fact that during December (Early? Mid?) the Adelaide Hills receive climatologically significant rains.

Edit:
  • A constant to the power of a function of precipitation is proportional to the dry interval.

The 24.2 mm we have received since the 12th of October have not significantly contributed to streamflow. The local river is now nearing levels seen in early winter.

Most indicators suggest we are tending toward a more humid, sub-tropical climate with higher humidity, less evaporation, more precipitation (under humid conditions), more thundery showers and higher dewpoints. Just recently (checking the humidity) the recorded maximum was 90%.

A contradiction to increasing rainfall may be that higher surface air temperatures (due to humidity – the greenhouse effect) mean the atmosphere can hold more moisture, so it may not be so unexpected to get numerous dry periods.


Edited by -Cosmic- (25/10/2010 15:44)

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#893484 - 25/10/2010 15:47 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
It might also be worth noting that while evaporation is falling, evapotranspiration appears to be increasing. This suggests longer growing seasons and possibly greater plant nutrient uptake. Evaporation has a potentially signficant impact on streamflow magntiude, evapotranspiration more so.


Edited by -Cosmic- (25/10/2010 15:49)

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#895310 - 02/11/2010 16:38 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills

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#895323 - 02/11/2010 17:37 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
A couple of photos of flooding from the Southern Highlands, New South Wales, in October:

Flooding in the Southern Highlands 1, NSW

Flooding in the Southern Highlands 2, NSW

And Wangaratta, Victoria:

Flooding Near Wangaratta

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#896183 - 07/11/2010 13:20 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: Unstable
I've got a clear view of the upper part of a shower to my south-east which is going along the range and it's well and truly glaciated smile

Yes, started hailing at about 4:50 this afternoon, for about 10 mins smile. Reasonable size hail, probably 3-5 mm across.

Peak winter-spring flow occurred on the 3rd of September, after approximately 57.8 mm fell in a 24-hour period to the morning of the 4th. This is backed up by a CDAS-NCEP/NCAR Reanalysis which shows the latent heat flux peaking during this time for the year. Also, according to the Reanalysis, the pressure dropped to about 990 hPa mid-morning on the 4th of September, and averaged 997 hPa during the day (in-field measurement: 997). 5 days later on the 9th, the pressure was again around 997 hPa (in-field measurement), which occurred during the onset of isolated severe weather conditions. Statistically, the earlier September rains are the most significant for this year (to date).

Although it is becoming increasingly unlikely that another peak in streamflow will occur in the next 2 months that will exceed that for September, I cannot yet rule out a peak occurring in December, after looking over several streamflow histories for the Adelaide Hills. In more recent days, while flow has not increased significantly (if at all), temperatures and humidity and been more conducive to outbreaks of severe weather conditions. The GFS rainfall forecasting model has been somewhat accurate in the last week – it predicted a moderate rainfall for late October leading into early November, which occurred, follow by intermittent smaller rainfall events in the following days (30th to 7th), which has also happen.

On the 31st, we experienced a moderately intense downpour of hail (10-15 minutes of pea-sized hail), possibly with some sleet (not an exaggeration). The temperature trend that followed this event plummeted to such an extend it felt like winter again (very clear fog on the breath). It was an isolated cold snap, possible very isolated, but very sharp and contrasting in terms of the impact had on the surrounding environment (the temperature dropped to perhaps 7-8 C in the mid afternoon, when you would normally expect it to peak). Considering we were averaging day-time maximums of between 17 and 25 degrees, this was definitely outside that range. The most recent pressure low was 996 hPa on the 29th. It's currently 1004.

It is enough to say recent conditions have been conducive to outbreaks of severe weather events, which is another reason why I’m not ruling out a peak in flow next month.


Edited by -Cosmic- (07/11/2010 13:29)

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#896186 - 07/11/2010 13:32 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Although it might give more context, the quote in the above post is a button-click error smile.

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#897088 - 10/11/2010 21:58 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
There is a significant period from 1987 to 1998 during which no rainfall was recorded for Woodside (23829). I have made attempts to fill the missing data on both 9 am to 9 am periods and 12 am to 12 am periods. Unfortunately no corresponding streamflow records exist against which I could compare any streamflow estimates locally; the nearest catchments covering the time period of interest (1970 to present) are Dawesley to the east and Lenswood to the west.

On another note:

It might be worth getting a copy of the History of Significant Flood Events in South Australia, 1836 – 2005. It includes synoptic charts and analyses.

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#897357 - 11/11/2010 20:51 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The air pressure hit a new yearly low (from what I can tell) today: 992 hPa. eek. It has been pretty sultry and threatening to rain since mid-afternoon. Was still 25 degrees at 7 pm.

Despite the dry conditions, the river continues to run rather reasonably for this time of year. It's certainly taking a while to dry out - suggests the latent heat is right up, and with it the wet-bulb temperature.

Also we appear to have experienced greater flows to this point this year than we have in previous 2-3 years. The last time we had signficant winter flows was in 2004 and 2005.

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#897938 - 13/11/2010 21:53 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The Barometric Pressure Over the Last 24-Hours (Lower Needle)



Streamflow Today and River Conditions:



5.8 mm, good soaking rain smile.


Edited by -Cosmic- (13/11/2010 21:56)

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#897948 - 13/11/2010 22:19 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The difference between the streamflow level in the photo above and that about a fortnight ago is barely noticable.

Also, Compare Peak 2009:



With Peak This Year:



Higher this Year…About August-September


Edited by -Cosmic- (13/11/2010 22:22)

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#898030 - 14/11/2010 12:46 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Having looked over photographic evidence, I can pretty much confirmed that flooding of the Onkaparinga River Occurred in September 1991 and August 1992. Less well known is a potential flood event which occurred in Septmber 1986.

The change in the landscape between the early 1990s and now is also dramatic.

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#900260 - 23/11/2010 14:56 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Estimates for streamflow modelling of the Onkaparinga River based on data 1/1/1974 to 31/12/2009:

Peak flow 2009: 26th of August.

Estimated flow: 0.0313 Mega Litres. (31.3 cubic metres)
Estimated Evapotranspiration: 2.1 mm.
Estimated rainfall: 12.4 mm on the 26th (42.2 mm on the 25th).
Estimated soil moisture store: 191.2 mm.
Estimated groundwater store: 4.4 mm.

Actual flow at Hahndorf: 1237.19 Mega Litres. (1237190 cubic metres)

Highest recorded flow in that period: 30/9/1996:

0.0722 Mega Litres Woodside (72.2 cubic metres)
10,794.58 Mega Litres, Hahndorf. (10,794,580 cubic metres)


Edited by -Cosmic- (23/11/2010 15:03)

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#901465 - 27/11/2010 19:50 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
A base flow analysis of Hahndorf observations suggests it is a little more difficult to model the Onkaparinga Catchment upstream than shown above.

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#901607 - 28/11/2010 16:36 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
I have a sneaking suspicion there's another peak in the flow coming...

5.8 mm to midday.


Edited by -Cosmic- (28/11/2010 16:43)

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#901840 - 29/11/2010 15:20 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Special Notes:

Onset of Convective Instability (Late Spring):

T: 30 C, RH: 20%, P: 1006 hPa.

Onset of Cool Easterly Winds after Highly Unstable Electric Atmosphere (Late Spring):

T: 35 C..?


Edited by -Cosmic- (29/11/2010 15:24)

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#901841 - 29/11/2010 15:31 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
16.8 mm since the 24th.

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#901928 - 29/11/2010 20:43 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The current synoptic situation is reminiscent of that for the 6th of February 1925, when significant flooding occurred in Adelaide.

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#901942 - 29/11/2010 21:06 Re: Streamflow Observations [Re: Seina]
teckert Offline
Weatherzone Moderator

Registered: 27/05/2001
Posts: 17706
Loc: NE suburbs, Adelaide, South Au...
You have a map for that date Carl?

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#901947 - 29/11/2010 21:09 Re: Streamflow Observations [Re: teckert]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: teckert
You have a map for that date Carl?
Yep, and a descrption smile!


Edited by -Cosmic- (29/11/2010 21:13)

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#902010 - 29/11/2010 23:36 Re: Streamflow Observations [Re: Seina]
Max Record Offline
Weatherzone Addict

Registered: 18/04/2009
Posts: 1668
Loc: Adelaide
100mm+ for a locale in Adelaide? Got any crazy dares I can do if that comes off? wink

Places in the Mid North copped that, too:

5 2 1925 Hallett (Ulooloo Railway Siding) 127.0
6 2 1925 Snowtown (Condowie) 108.0
6 2 1925 Terowie (Parnaroo Sect 50) 102.9
7 2 1925 North Adelaide 163.6
7 2 1925 Adelaide (West Terrace) 141.5
_________________________
2019: 185.8mm
2018: 329.2mm
2017: 478.0mm
2016: 680.0mm
2015: 392.8mm
2014: 450.4mm
2013: 470.6mm
2012: 426.8mm
2011: 518.2mm
2010: 549.4mm
2009: 459.2mm
Yearly Average: 460mm

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