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#1146699 - 01/12/2012 16:29 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Flash flooding reported in BoM Severe Thunderstorm Warning issued 8:33 pm yesterday.

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#1148670 - 11/12/2012 18:05 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
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Loc: Adelaide Hills
Estimated precipitable water (PWAT) values for the previous event (circa. 29th Nov-1st Dec 2012) reached 25.3 mm specific to this area, not 35-40, let alone 40-45.

Think their yet to come, give it half a week smile .
[Note: Not a forecast see official forecasts].


Edited by -Cosmic- (naz) (11/12/2012 18:14)

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#1149180 - 13/12/2012 18:43 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Loc: Adelaide Hills
Written 11th Dec 2012 (updates italicised):
Recent GFS model runs suggest a gaping hole (area of relatively unstable low pressure) may form across the interior of Australia, bringing with it the formation of several consecutive lows forming along the northwestern coast and associated troughs (see Analysis for 06:00 UTC on Thursday 13 December 2012), allowing copious amounts of moisture to reach more southern areas of the continent, within a week.

The potential for this system, for widespread falls significantly more marked that those of the previous system seems (for Central Areas – Adelaide – and probably further to the northwest and southeast) much higher. 20-40 is some areas not out of the questions, much more robust moisture presence, relatively high CAPE sliding across the land-ocean boundary between WA and SA.

I consider it pretty early to be making these kinds of assumptions about this sort of event, and this is just my view (thing could change in the mean time), but this may have been developing from some time. Better to be prepared than not.

Update 13th Dec 2012:
Rough [expected] outcomes don’t seem to have changed.

CAPE remains relatively high, moisture likely to start picking up into night-tomorrow morning. Overnight low was 19, currently 25 after 37 with cloud-cover developing, humidity is rising (current up ~6%/3 hours from 40%).

Possible order magnitude change in flow.

On a side note, will a hypothesis re: relationship between humidity and soil moisture be supported in this case? Or even precipitable water?

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#1149579 - 15/12/2012 10:29 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
will a hypothesis re: relationship between humidity and soil moisture be supported in this case? Or even precipitable water?

8.6 mm soil moisture smile .

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#1151050 - 19/12/2012 17:02 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Written 11th Dec 2012 (updates italicised):
Recent GFS model runs suggest a gaping hole (area of relatively unstable low pressure) may form across the interior of Australia, bringing with it the formation of several consecutive lows forming along the northwestern coast and associated troughs (see Analysis for 06:00 UTC on Thursday 13 December 2012), allowing copious amounts of moisture to reach more southern areas of the continent, within a week.

The potential for this system, for widespread falls significantly more marked that those of the previous system seems (for Central Areas – Adelaide – and probably further to the northwest and southeast) much higher. 20-40 is some areas not out of the questions, much more robust moisture presence, relatively high CAPE sliding across the land-ocean boundary between WA and SA.

I consider it pretty early to be making these kinds of assumptions about this sort of event, and this is just my view (thing could change in the mean time), but this may have been developing from some time. Better to be prepared than not.

Update 13th Dec 2012:
Rough [expected] outcomes don’t seem to have changed.

CAPE remains relatively high, moisture likely to start picking up into night-tomorrow morning. Overnight low was 19, currently 25 after 37 with cloud-cover developing, humidity is rising (current up ~6%/3 hours from 40%).

Possible order magnitude change in flow.

I believe a few things might need clarifying regarding the above smile .

Calculating basic precipitable water (PWAT) can be achieved using this link (looking down the list of parameters we find “W”). This indicates (the equation) that if PWAT is to increase while the pressure is falling, the humidity has to rise substantially (perhaps sustained at or above about 78-80% for 2-3 days or more), the temperature falling during or after a pressure trough. So far this has not happened enough to result in direct runoff (the expected part), and it remains to be seen for the remainder of the year (as the pressure continues on its annual falling trend into mid-summer) whether this will actually happen. The 20-40 mm thought to be “not out of the questions” was intended for the “relatively high CAPE sliding across the land-ocean boundary between WA and SA”, where some rain, according to the Bureau's last 1-week mapped rainfall totals to the 18th (yesterday) did fall in that bracket, even thought not really over SA (although it would have been nice smile ).

It is apparent there is an increasing presence of moisture (as well as the soil moisture mentioned in the last post) in the last few days. Streamflow remains steady/stagnant.


Edited by -Cosmic- (naz) (19/12/2012 17:04)

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#1151707 - 22/12/2012 10:51 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
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Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
It is apparent there is an increasing presence of moisture (as well as the soil moisture mentioned in the last post) in the last few days. Streamflow remains steady/stagnant.

Correction: (streamflow) water level more likely falling. The green tinge in the paddocks is fading.

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#1151711 - 22/12/2012 11:41 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Loc: Adelaide Hills
#1106840 - 30-05-2012 02:58 PM:

Originally Posted By: -Cosmic- (naz)
Not looking that flash for Central SA for the coming winter…nor Southwest WA frown .

Update for the Southwest Corner (WA)

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#1153356 - 29/12/2012 12:21 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Originally Posted By: -Cosmic- (naz)
It is apparent there is an increasing presence of moisture (as well as the soil moisture mentioned in the last post) in the last few days. Streamflow remains steady/stagnant.

Correction: (streamflow) water level more likely falling. The green tinge in the paddocks is fading.

Definitely falling and fading.


Edited by -Cosmic- (naz) (29/12/2012 12:27)

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#1159080 - 16/01/2013 18:54 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
For information:
#1151050 - 19-12-2012 05:02 PM:

Originally Posted By: -Cosmic- (naz)
This indicates (the equation) that if PWAT is to increase while the pressure is falling, the humidity has to rise substantially (perhaps sustained at or above about 78-80% for 2-3 days or more), the temperature falling during or after a pressure trough.

Bold Added.

The outdoor hygrometer recorded 78-80% near the peak of onset of 12.5 mm of rain on the 13th (Jan, Sunday), which lasted for a period of 4-5 hours. This was sufficient to make a very slight difference to stream flow water levels, in addition to soil moisture.

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#1163537 - 23/01/2013 17:55 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
The water level is falling at different rates along different parts of the local river. In some areas there is no water left (it's all evaporated, about 0.25 to 0.5 metres of it), while in others it's receeding at perhaps 1-2 inches a day, less with cloud cover or even, recently, steadying with some rain. It seems very dynamic.

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#1170160 - 02/02/2013 21:57 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
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Loc: Adelaide Hills
Records indicate it may take approximately 10 mm (in one day) – from 2/2/2013 (today) – to increase water levels to those seen on the 4th of February last year, or about 300 to reach those witnessed in early September 2010.

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#1170223 - 03/02/2013 11:53 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Stream flow water-levels observed on different days in a single location at about the same time in February 2012 and 2013. Might give some idea of what I meant by water levels falling.

1st February 2013:


4th February 2012:

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#1171244 - 10/02/2013 10:05 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Prelim note: potential for trend-breaker by end of month.

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#1171493 - 11/02/2013 14:01 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Prelim note: potential for trend-breaker by end of month.

Refer to 28-day outlook for "high" probability from this link (19th-20th, note link will update).

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#1172394 - 15/02/2013 20:12 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Major immediate runoff and torrential rain from thunderstorm(s) (7.45 pm)!

Potential flash flooding risk!??


Edited by -Cosmic- (naz) (15/02/2013 20:21)

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#1172500 - 15/02/2013 22:29 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Potential flash flooding risk!??

Subsided.

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#1172671 - 16/02/2013 11:44 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
A few inches increase in stream flow water level overnight laugh . Most has evaporated if not is already doing so.

Not enough time during the event to get any proper footage, but basically:

5 mins: heavy/torrential rain.
10 mins: gutters over flowing.
15 mins: water lapping at 2-3 inches deep in places.
20 mins: see "potential flooding" comment.

Probably the biggest (most prolonged and intense) convective rain event in many years.


Edited by -Cosmic- (naz) (16/02/2013 11:47)

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#1172839 - 16/02/2013 22:19 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
A few inches increase in stream flow water level overnight laugh . Most has evaporated if not is already doing so.

Hence not trend-breaking in terms of an easing of dry conditions...and the 19th-20th might have a little last-minute uncertainty as well.


Edited by -Cosmic- (naz) (16/02/2013 22:20)

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#1173835 - 20/02/2013 13:48 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Prelim note: potential for trend-breaker by end of month.

The potential for a break in dry conditions remains - by the end of the month - but not over the period 19th-20th. While the maximum temperature fell 14 degrees from the 18th to the 19th (the minimum remained roughly the same), and the humidity rose somewhat, conditions were generally windy with only a trace of precipitation...hence a trend was only broken in statistical terms.

Hopefully this is a prelude to something more smile , but I cannot guarantee that, hence potential, not actual.

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#1175570 - 24/02/2013 11:11 Re: Streamflow Observations [Re: Seina]
Seina Offline
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Registered: 27/08/2003
Posts: 7769
Loc: Adelaide Hills
Stream flow is gradually approaching levels of March 2010, so in many parts the river is now dry (there is no water level so I'm basically talking about isolated/disconnected pools of water). These pools appear to be either fairly deep or have the ability to retain moisture somehow.

The recent trend of falling water levels is very real...and with each passing day/week it seems to get more eye-opening. Any rain that falls needs to fall at such a rate that in gets into the soil first, with minimal runoff, although runoff that doesn’t evaporate within hours of rain falling would also be welcome – for that the evaporation rate also needs to fall (related to solar heating/cloud cover).

Looks like the best chance for a change in the water level (of any appreciable amount) might be tonight, into tomorrow (according to GFS, assuming the forecast doesn't change in the mean time). Will see smile .


Edited by -Cosmic- (naz) (24/02/2013 11:19)

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