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#1461329 - 09/04/2018 20:54 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Based on observations of broader to smaller scale weather dynamics in the Australian region [since about the 19th of March this year], the next probable significant [maximum] temperature change [fall] and increase in dew-point for the Greater Adelaide Area, seems to be starting within the next 3 days -- by the 12th. Any showers and/or rain needs to be steady-enough [overall] to avoid stripping top soil or causing landslides.


Edited by Seira (09/04/2018 21:03)
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#1462494 - 24/04/2018 22:29 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Originally Posted By: Seira
Based on observations of broader to smaller scale weather dynamics in the Australian region [since about the 19th of March this year], the next probable significant [maximum] temperature change [fall] and increase in dew-point for the Greater Adelaide Area, seems to be starting within the next 3 days -- by the 12th. Any showers and/or rain needs to be steady-enough [overall] to avoid stripping top soil or causing landslides.

Some top soil stripped from paddocks [haze] – due to stronger northerly winds leading up to the initial change (on the 12th of April), rather than from rain. Rainfall was about 38.6 mm over 4 days [14th-17th of April]; slight run-off. Most significant rainfall/shower period since Late November-Early December 2017 in the Greater Adelaide Area.

Many daily maximum temperatures in the vicinity of the Greater Adelaide Area [GAA] fell by 10-to-15 degrees between the 11th and 12th of April, while minimums maintained at about their pre-12th variability. A surface low with multiple associated NNW-SSE … (across the interior, towards Broome WA, and near Esperance) … and WNW-ESE (across the Tasman Sea, towards New Zealand) surface troughs formed near Kangaroo Island [KI] in front (east-of) an approaching longer-wave trough. This longer-wave trough was approaching from the Deep SW (south of Albany WA). The surface troughs [extending from the KI surface low] implied upper ridge conditions, with milder upper tropospheric temperatures, running from the upper-ridge centre – NNE of Adelaide – towards Queenstown Tasmania. This generated a somewhat unstable environment in which a narrow band of shower activity could pass mostly SE of the GAA.

The change in the maximum daily temperatures allowed water-vapour, siphoning along the NNW-SSE surface-trough/s, to drifting SSE along a temperature and pressure gradient. This was moisture moving from a higher pressure and temperature environment, to a lower one. Then uplifting to form cloud. This cloud consequently became thicker further SSE, and more convective in nature, generating mildly steeper lapse rates, with minimum temperature variability remaining mostly static.

This change in the maximum temperature [12th of April], combined with NNW-SSE-aligned surface troughs –provided the impetus for a change in the wind-direction from easterly (NE-SE) to more westerly. The eastward movement of the KI surface low would have allowed this wind-change to occur more than once along multiple trough-lines. These surface troughs were a convergent boundary, where the axis of the KI surface-low, also drifted from a previous front (moving towards New Zealand).


Edited by Seira (24/04/2018 22:30)

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#1465642 - 15/06/2018 00:05 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Local [Adelaide Hills] run-off is beginning to [measurably] respond to rainfall in the last few days smile .
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#1465746 - 16/06/2018 16:29 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Looks like a middle-to-upper-level shorter-wave trough has arrived in the Greater Adelaide Area; accompanied by a now-easterly-moving surface counterpart. Southern-to-Polar Maritime air-streams now mostly prevailing. Let's see how observations go overnight smile .


Edited by Seira (16/06/2018 16:38)
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#1467012 - 06/07/2018 21:49 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Originally Posted By: Seira
Looks like a middle-to-upper-level shorter-wave trough has arrived in the Greater Adelaide Area; accompanied by a now-easterly-moving surface counterpart. Southern-to-Polar Maritime air-streams now mostly prevailing. Let's see how observations go overnight smile .

Observations demonstrated the frequency and intensity of showers along the said air-streams were insufficient for additional, significant changes to run-off in the area…

In fact, nowhere across the country recorded additional, significant changes to run-off from "Below Flood Level" that are apparent, even with much higher falls across the Victorian Alps.

--------------------------------------------
Today (6th of July):

Potential for reasonable run-off overnight into tomorrow within the Greater Adelaide Area, that is by the 8th of July.
[Intense rainfall exceeding 20 mm recorded in the last 24 hrs. Local stream flow response evident.]


Edited by Seira (06/07/2018 21:58)
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#1467118 - 08/07/2018 20:19 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Originally Posted By: Seira
Originally Posted By: Seira
Looks like a middle-to-upper-level shorter-wave trough has arrived in the Greater Adelaide Area; accompanied by a now-easterly-moving surface counterpart. Southern-to-Polar Maritime air-streams now mostly prevailing. Let's see how observations go overnight smile .

Observations demonstrated the frequency and intensity of showers along the said air-streams were insufficient for additional, significant changes to run-off in the area…

In fact, nowhere across the country recorded additional, significant changes to run-off from "Below Flood Level" that are apparent, even with much higher falls across the Victorian Alps.

--------------------------------------------
Today (6th of July):

Potential for reasonable run-off overnight into tomorrow within the Greater Adelaide Area, that is by the 8th of July.
[Intense rainfall exceeding 20 mm recorded in the last 24 hrs. Local stream flow response evident.]

Rainfall, all ~ 37 mm of it since 12 am on the 5th, contributed to a mild-to-modest change in local run-off smile .


Edited by Seira (08/07/2018 20:19)
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#1467446 - 16/07/2018 20:50 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7469
Loc: Central Adelaide Hills
Another period of intensification of the longer-wave upper-trough system is approaching Southern Australia. Potentially rainfall in the range 10 to 40 mm+ between approximately Port Lincoln, Adelaide and Mt. Gambier SA. That's one way of looking at it anyway smile . It seems likely there will be a period before about the 20th-22nd [of July] when the day-night temperature range will moderate substantially, while the dew point remains high, relative to the overnight low. It's already on the Bureau's forecast by the looks of it.
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