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#1210680 - 17/09/2013 21:43 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Flow levels yesterday reached a height (station 523714) not seen since about the 13th of August. 15.9 mm in the last 3 days smile . 47.4 since the 5th.

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#1210687 - 17/09/2013 23:49 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Written 12.20 pm 12th September 2013:

An estimate of possible falls indicated (Wednesday 11th) the highest probability of a noticeable change in streamflow would be Sunday-Monday next week. The other (smaller) potentials were Tuesday (10th) and Friday (tomorrow). Tuesday had a similar potential to next Monday with similar surface pressure (995-996 hPa). The total [rainfall] Thursday to next Friday was ~ 43 mm (11th), and is now something like 67 (12th).

Update (15th): It now seems possible the pressure will remain relatively low for 2-3 days from Sunday (probably mid-990s, 5.15 pm CST pressure 994 sfc) could be looking at some rather large totals. CAPE is forecast to be considerable for the (2-3 day) period (GFS) given recent systems.

Seems heavy downpours may be possible across SA over the next 48-72 hours.

There also seems to be a higher probability for Thursday (19th) however it is some time out (in daily terms).

Update (17th): Thursday system now Tues-Wed smile !? Another 10-15 mm or more!?

Total rainfall 12th-today: 42.8 mm (9 am).

Sfc. Pressure 991 hPa 16th.

[Disclaimer: Guide Only]

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#1210723 - 18/09/2013 13:55 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
The infiltration process has been below saturation level for a while (days to weeks) now locally, so that seems another good sign - it means the moisture from previous systems has soaked in, so there's then a change in the capacity of the [catchment] system to store / retain moisture before runoff occurs.

It has taken some time (months), but in the space of less than 12 hours, the water level rose from something like 0.25 m to 0.91 (see previously mentioned site).

The river after 14.7 mm this morning:




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#1210736 - 18/09/2013 16:19 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Above photos taken at ~ 8.50 am CST.

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#1211098 - 22/09/2013 13:40 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
The total [rainfall] Thursday to next Friday was ~ 43 mm (11th), and is now something like 67 (12th).

Total rainfall for the period 12 am Thursday 12th of September to 12 pm Saturday 21st September 2013 was 67.2 mm.

Local streamflow (523714) has subsided back to about 0.2 m.

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#1211261 - 23/09/2013 22:57 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

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

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#1212896 - 09/10/2013 13:35 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
[In my view] slight potential for downpour/s in (over) the next week. Moderate potential for showers. Expected impact on streamflow depends on rain rate roughly:

- 5-10 mm/day (slight, showers) (say 70% chance);
- 10-20 mm/day (slight-moderate, showers/rain) (half of 70%);
- 20-40 mm/day (moderate, rain) (1/3 of 35%);
- 40-80 mm/day (significant, downpour/s) (1/3 of 12%).


Edited by -Cosmic- (naz) (09/10/2013 13:39)

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#1213854 - 16/10/2013 17:18 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Impact of rain/showers on streamflow over the last week has been minimal; less than 10 mm recorded.

Overnight low has been roughly stable since about the 28th of August, however is showing signs of declining again [actual decline yet to be seen].


Edited by -Cosmic- (naz) (16/10/2013 17:19)

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#1214407 - 21/10/2013 15:30 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Visible increase in stream flow without rainfall yesterday (20th Oct); cause unknown.

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#1215036 - 25/10/2013 16:31 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Impact of rain/showers on streamflow over the last week has been minimal; less than 10 mm recorded.

Overnight low has been roughly stable since about the 28th of August, however is showing signs of declining again [actual decline yet to be seen].

30.1 mm recorded since the 10th of October. Negligible impact on flow.
More zero/sub-zero overnight lows now apparent.

Originally Posted By: -Cosmic- (naz)
Visible increase in stream flow without rainfall yesterday (20th Oct); cause unknown.

Cause remains unknown, possibly natural.

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#1216593 - 05/11/2013 16:53 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Written 1st November 2013, [added 3rd]:

Originally Posted By: -Cosmic- (naz)
Originally Posted By: -Cosmic- (naz)
Impact of rain/showers on streamflow over the last week has been minimal; less than 10 mm recorded.

Overnight low has been roughly stable since about the 28th of August, however is showing signs of declining again [actual decline yet to be seen].

30.1 mm recorded since the 10th of October. Negligible impact on flow.
More zero/sub-zero overnight lows now apparent.

The minimum overnight low now appears to have broken through the 5-degree threshold lowered, while the maximum (since the 28th) is gradually increasing, suggesting a shifting diurnal range; its increasing. An increasing diurnal range may imply lower dew-points and lower humidity. Since the 10th of October a general fall in the relative humidity from about 60% to around 35-40% has been observed. In theory soil moisture has also fallen in that time with increased evaporation and reduced cloud-cover, which now seems apparent since the last weather system to affect the soil (14 mm rain 16th-17th last month).

The minimum temperature profile since the 1st of August almost resembles a mirror reflection.

All of this seems to indicate the dew-point temperature is going increase this month, which may mean the pressure peaks before falling somewhat, or precipitable water increases, or both. [If both occur, the diurnal range could narrow]. In any case, the chance of [steady] rainfall is increased under the condition of more moisture [and increased cloud-cover] in the atmosphere smile .

Today:
The next period with a chance of rain or showers [Bureau] could affect run-off as well as soil moisture.

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#1217070 - 09/11/2013 11:11 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
10.5 mm to 9 am in the last two days. No run-off.

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#1218246 - 13/11/2013 13:51 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
For those interested:
It seems the [upper north-eastern quadrant of the] sub-tropical ridge has become a prevailing feature in recent times (days to weeks) across [much of] Southern Australia. From my own point of view it suggests cooler-to-cold days and nights and the possibility of showers. There is evidence present in the literature (Ummenhofer et al. 2009; Evans et al. 2009; Larsen and Nicholls (2009); Risbey et al. (2009); Nicholls, 2010) which could give some indication as to whats going on relating to this feature.


Edited by -Cosmic- (naz) (13/11/2013 13:59)

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#1220121 - 18/11/2013 15:39 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
A moderate flood warning has been issued by the Bureau of Meteorology for the Paterson and Williams Rivers on the Mid North New South Wales Coast at 1:42 pm EDT on Monday 18 November 2013. It is said an average of 170 mm has fallen in the 28 hours to 1 pm today. The Bureau also made a note about how predictable further river rises in the region may be due to rainfall uncertainty.

The River Height for Paterson River at Gostwyck Bridge (station 61349) rose from approximately 1.19 to 11.57 metres between 23:15 pm EDT yesterday (17th) and 14:45 pm EDT today. Major Flood Level is 12.20 metres.

See the NSW flood warnings for more information.


Edited by -Cosmic- (naz) (18/11/2013 15:44)

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#1222087 - 25/11/2013 13:29 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The prior event (previous post) remained at moderate flood level although water levels continued to rise for some time within that flood class.

------------------------------
*[The following is opinion based on observations and publicly accessible computer models]*

Written 24th of November 2013 [Updated from the 21st]:
At this stage there may be a potentially significant rain event pending by the end of the month. Timing could be circa 28th, but rainfall is uncertain due to probable changes between now (24th) and then over the passage of an upper-level trough near a surface high-pressure ridge during that time south of the Bight. Yesterday (23rd), both GFS and ACCESS-G mostly agreed on a scenario, however a question remains about likely rainfall totals and how widespread they will be. Based on uncertainties (today), anywhere up to 70 mm, 20-30 might be a reasonable middle ground.

It seems there is potential including pre-event changes in multiple weather variables (based on models mentioned earlier), however despite this, it could still take until the last 12-24 hours.

Update 25th: Dynamics still very similar (ACCESS-G and GFS), now possibly affecting most of Southern Australia. South-eastern states likely to follow. General falls anywhere between 5 to 10 mm and 50 to 70. Moderately humid northerly winds ahead of the change (WZ forecast for South Australia).


Edited by -Cosmic- (naz) (25/11/2013 13:34)

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#1222509 - 27/11/2013 14:52 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Correction to wind direction transition between now mostly dry northerlies (observatons) and humid southerlies (Bureau forecast) likely over the next 24 hours.


Edited by -Cosmic- (naz) (27/11/2013 14:57)

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#1222810 - 29/11/2013 13:30 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Cool change with 3.4 mm of light rain/drizzle to 6 pm last night (enough to wet the ground). Temperature dropped from 35 to 15 degrees (max to max) - 20 degrees. No run-off; models downgraded in the last 24 hours prior to the change, although the humidity increased. It is conjectural whether any connection can determined between the change in humidity and soil moisture for this one event.

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#1223077 - 30/11/2013 18:25 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Some December rains may be approaching [according to the Bureau] ... smile .


Edited by -Cosmic- (naz) (30/11/2013 18:26)

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#1223556 - 03/12/2013 17:47 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Written 1st December 2013 (Updated 3rd):

Originally Posted By: -Cosmic- (naz)
Some December rains may be approaching [according to the Bureau] ... smile .

During the last noticeable change [in weather conditions conducive to significant falls] the specific humidity did not appear to reach a threshold which would have made forecast falls more likely (i.e. increased atmospheric water content/vapour pressure and reduced or unchanging barometric pressure)...the models (those mentioned previously, ACCESS-R and G, GFS) now (from what I can tell) indicate a much sharper upper-level trough and broader high-pressure ridge. There could also [likely] be a noticeable change in the [500-1000 mb] thickness (experienced through a temperature difference). In any case the probability of said falls appears to be increased, with rainfall less uncertain, maybe 10-20 mm over the next week for Central Areas (based on WZs recent Mount Barker forecast [1st to 3rd]).

The likely impact on streamflow is probably going to be through additional soil moisture my opinion is it would take something in the order of 20-40 mm in the first 24-48 hours of the next few days (12 pm CDT today forward) to see appreciable run-off. At the moment those sorts of dynamics (i.e. high precipitable water, consistent 80%+ relative humidity (lower-to-middle level moisture), low pressure and a sharp reduction in thickness) just arent apparent (although I could be mistaken). This system seems to currently favour intermittent convective activity with sharp moderate-to-heavy rain. If were going to get hail, that might be where it comes from; that said, if the thickness continues on its current path (as forecast by ACCESS-R), hail showers might be possible.

This system is also tracking east, which could make the dynamics which unfold after crossing the (Southeast) coasts maybe a bit more interesting.


Edited by -Cosmic- (naz) (03/12/2013 17:50)

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#1224305 - 08/12/2013 18:52 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Possible revision of likely totals to week ending 9th Dec 2013 (20-40 mm) if specific humidity reaches 0.01 kg/kg by early tomorrow morning and diurnal temp range sharpens enough smile . See BoM Adelaide forecast 4.10 pm CDT.

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