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#1427834 - 11/07/2017 18:13 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Modest Streamflow Response, Adelaide Hills:
5th to 8th of July 2017, following a Mostly Dry June


[Grammatical errors may persist despite editing]

18th of June 2017:

Sometime back between the 5th and 10th of June, the longer-wave trough, to the south of the Bight, sent a shorter-wave (upper-to-middle) off-shoot north-east [from south of Tasmania]. This off-shoot was subsequently undercut by the [surface] sub-tropical ridge (“<” shaped, with the “\” being the undercut), changing the wind-direction from westerly to north-easterly on the eastern flank of the offshoot. It was thus lodged in a region between about Melbourne and Brisbane.

As the sub-tropical ridge directed E-to-ESE winds over interior Victoria from the south, moisture became diffuse and dissipated the further inland the winds moved (the Inter-Tropical Convergence Zone and 576-thickness contour situated near/north of Darwin, NT). With a lower tropospheric thickness, this absence of [inland] moisture (its accumulation, had temperatures possibly been higher) did not occur, hence dewpoints fell. The lower thickness would have then extended to sub-zero overnight lows, while the day-time maxima barely change (between Adelaide SA, Wollongong NSW and Melbourne VIC). Hence frost conditions ensued in the absence of sufficient cloud-cover.

Both the sub-tropical ridge and the main long-wave trough to the south of the Bight have been pushing east and NE, respectively. With the lodging of the tropospheric disturbance (on the East Coast between Melbourne and Brisbane), subsequent longer-wave troughs or lows (upper, middle or lower) have been unable to dislodge this disturbance. Thus, moisture north of the 576-thickness contour was tapped into [from the NE] in the Coral Sea [at the surface level]. This meant the middle-to-upper disturbance becoming lodged (again) west, against the Great Dividing Range, sustaining itself. The main longer-wave troughing (in deep south) has been continuing to push northeast.

The current pattern affecting SA (as 18th of June 2017) could change (properly) when the East Coast disturbance intensifies and moves further south. This would disrupt the west-to-east ridge movement, and shift the axis of the long-wave trough in the deep south, east. This is likely to happen in the next couple of days (19th to 22nd of June), with this transition forcing a part of the sub-tropical ridge in the South-eastern Indian Ocean (SEIO) to realign (“/_” shape). This would also likely mean a part of the same ridge over Adelaide would be compressed, in the north-south orientation (forming a “_>” shape). The upper longer-wave troughs and lows would then be forced (through southerly winds on the eastern edge of the SEIO ridge) onto the eastern flank of the Indian-Ocean high (23rd to 26th of June), generating another offshoot (middle-to-upper level low).

A recent 2 mm on the 16th of June went straight into the soil locally. Minima of -2 to -6 C were mapped by the Bureau on the 10th of June across the inland Southeast and interior of the country.

21st of June 2017:

The winds on the eastern flank of the South-Western Western Australia (SW WA) offshoot became stronger, with the surface-based sub-tropical ridge continuing to push northeast. Simultaneously, the main long-wave trough south of the Bight (axis now shifted) blocked the southerly movement of the offshoot, forcing it up the WA Coast, and towards Adelaide (23rd to 26th of June). This meant winds on the south-eastern flank (with higher dewpoints and moisture content from the deep-south front) were dragged across SW WA. These ESE winds became affected by orographic uplift and land-sea temperature differences (warmer land). This generated heavy rain at several inland weather and streamflow sites (posted 23rd of June).

This is now starting to align the surface ridges “/_\” where “_” is the long-wave upper trough. This will likely release the SW-NE movement of the troughing [it becomes sharper and deeper], the pattern changing (between about the 27th of June and the 1st week of July).

26th of June 2017:

No significant changes to dynamics.

Streamflow levels (creeks/rivers/run-off) could possibly be affected by about early-mid July [2017] [SA].

30th of June-2nd of July 2017:

Possible rainfall range Sunday (late) 2nd to Thursday 6th of July: 15-40 mm.
Recorded: ~44 mm.

Estimated maximum rainfall (same period): 50 mm (Adelaide area).
Estimated region boundary: Whyalla to Mildura, to Omeo, to Melbourne to Port Lincoln.
Estimated run-off, minor-to-moderate (all run-off).

Rainfall of 50 to 99 mm recorded, followed by additional 25 to 49 mm falls [in SW WA region] as this system approaches (to 9 am, 2nd of July).

4th of July 2017, 5.25 pm ACST:

Streamflow levels (creeks/rivers/run-off) started responding (increasing) at 4 am, 3rd of July, with another storm at about 4 pm today increasing levels again.

Severe weather warning for heavy rainfall issued 4th of July, 4.45 pm ACST, another not long after.

Revised rainfall (4th): 50-80 mm in next 24-48 hours.

7th of July 2017, 9.15 pm ACST:

Recorded: ~34 mm last 3 days to 8.45 pm, 4th to 7th.

Streamflow now definitely responding (7th).
Bureau: 8 to 20 mm forecast tonight; 5 to 15 tomorrow.
At least 90% chance of any rain [6.44 pm ACST].

81.1 mm in 3 pm ACST, 10th of July, since 12 am on the 2nd of July (8 days). 69.5 more than all of June.

Disclaimer: as previous.

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#1428332 - 18/07/2017 15:21 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
The Upper Onkaparinga River stream level is responding to heavy rainfall: ~ 66 mm in the last 63 hours, 76 in the last week.

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#1428475 - 19/07/2017 21:01 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
The Upper Onkaparinga River stream level is responding to heavy rainfall: ~ 66 mm in the last 63 hours, 76 in the last week.

The flow at Woodside Weir reached 1.06 metres at 5 pm yesterday, after about 76 mm, 15th-18th, 12 am.

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#1428794 - 24/07/2017 20:36 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Chance run-off in/near the Adelaide Hills will be affected sometime between the 27th and the end of July.


Edited by Seira (24/07/2017 20:37)

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#1429207 - 29/07/2017 20:08 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
And so the rain/showers continue smile :

26/7/2017--0.2.
27/7/2017--6.5.
28/7/2017--0.
29/7/2017--6... (~7.35 pm ACST).

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#1429227 - 29/07/2017 22:01 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
29/7/2017--6... (~7.35 pm ACST).

13.2 ~ 9.30 pm.

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#1429322 - 30/07/2017 19:48 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
Originally Posted By: Seira
29/7/2017--6... (~7.35 pm ACST).

13.2 ~ 9.30 pm.

14.7 mm total yesterday (12 am-12 am). Mild run-off response.


Edited by Seira (30/07/2017 19:50)

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#1429426 - 31/07/2017 21:29 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
Originally Posted By: Seira
Originally Posted By: Seira
29/7/2017--6... (~7.35 pm ACST).

13.2 ~ 9.30 pm.

14.7 mm total yesterday (12 am-12 am). Mild run-off response.

11.5 mm (12 am to 9 pm, 31st), most before 9 am. Moderate run-off response.

Possible all-included run-off response by early-to-mid August: significant: 1.5-2 metres. Remote 2+.

Disclaimer: As previous.


Edited by Seira (31/07/2017 21:39)

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#1429835 - 05/08/2017 12:56 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
In about 9 hours, 15 mins, the upper Onkaparinga river at Woodside, in SA, rose 0.73 metres yesterday. Around 20 mm was recorded locally in that period. Be interesting to see what 50 mm (or even 90) does, if indeed it does fall.

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#1430518 - 13/08/2017 00:37 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
[Weather] pattern change due around Monday 14th.

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#1430795 - 15/08/2017 17:09 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
54 mm to 4.35 pm ACST, since midnight.

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#1430942 - 16/08/2017 22:46 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
54 mm to 4.35 pm ACST, since midnight.

Another 60-odd mm over the next 2 days to reach the maximum on the Bureau's forecast rainfall range (120 mm). Minor [barely exceeded] once in that time along the Onkaparinga; will see what happens next 24-36 hours.

Reasonably low 500-1000 mb thickness approaching Adelaide Area from the SW on an incline with a surface ridge and upper trough [surface pressure rising in low thickness], with more potentially Sunday-Monday.


Edited by Seira (16/08/2017 22:54)

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#1430944 - 16/08/2017 23:01 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Early signs of streamflow response as of ~ 10.25 pm SA local time.

Verdun overpass [between Balhannah and Verdun] showed a fairly substantial rise the afternoon of the last peak, which means it is not taking much for run-off to impact downstream. The response can/may become more rain-rate dependent as water has now had a decent time (between the last significant weather system] to soak into the surface soil, potentially making the soil prone to rapid response with intense-enough, frequent-enough rain-rates.


Edited by Seira (16/08/2017 23:08)

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#1430945 - 16/08/2017 23:31 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Also...the surface barometric pressure is behaving in a declining fashion, reminiscent of a transition from the Southern Spring into Summer...which clearly cannot be the case because Summer is usually characterised by lower, more frequent surface pressure, with less dramatic differences between higher- and lower-pressure.

The fact of the sustained decline from about early July, combined with a seemingly strong rainfall signature, suggest either there is a rather deep-trough period on the horizon, or the pressure going to rise (substantially), off the back of an upper trough, signalling another dry period.

Either way, for the pressure to rise it must fall first, if it is not already doing so.


Edited by Seira (16/08/2017 23:33)

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#1431470 - 22/08/2017 19:01 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
112 mm 15th of August (12 am) to 21st (3 pm)...highest run-off peak was 2.04 m (Bureau).

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#1432526 - 02/09/2017 17:30 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
The quantity of moisture that has soaked into the surface soil since 12 am on the 15th of August [126 mm] appears to be substantial. It may mean the is less "room" in the surface soil - and deeper layers - for further rainfall to soak in, which likely means more run-off if another 20-40+ mm falls within the next 5-7 days [with a robust change traversing a gap in the sub-tropical ridge].

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#1432583 - 02/09/2017 23:02 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Soil moisture [estimated] has now reached about the same level as it did just before last years [2016] streamflow peak (1000-1005 mm retention) or approaching 70-80% of available capacity as a rough guide.

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#1433212 - 07/09/2017 23:22 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Originally Posted By: Seira
The quantity of moisture that has soaked into the surface soil since 12 am on the 15th of August [126 mm] appears to be substantial. It may mean the is less "room" in the surface soil - and deeper layers - for further rainfall to soak in, which likely means more run-off if another 20-40+ mm falls within the next 5-7 days [with a robust change traversing a gap in the sub-tropical ridge].

Another 54.9 mm 12 am, 2nd to 8 pm ACST, 5th of September brings about a moderate change in all-combined run-off between ~ 0.1 and 1.1 metres, with variations within that range to-date. The flow response was rapid (Bureau) prior to 7 pm on the 3rd.

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#1434932 - 23/09/2017 22:26 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Longer-wave trough activity is approaching SW WA-Bight with a change in the SFC/MSLP pressure sub-1000 hPa (22nd-23rd of September) not seen since 28th of December 2016. Perth and South-of would be due for significant (20-40+) rain.

Rain in Perth WA, Mid-to-Late September 2017:

Perth is likely to receive 20-40+ mm in the next 24-48 hours as a surface low of 1004 hPa travelling at about 60-65 km/h (Bureau MSLP Analysis, 4 pm AEST) (with a pocket and/or plume of upper 500-hPa at temperatures of -20 to -30 degrees C) approaches from the WSW. Winds on the eastern flank look like they will be from the S-SE direction, drawing very strongly on westerly belt (Southern Ocean).

The surface winds appear to be arcing SE (Esperance) => NW (Geraldton) => NE => SE (Eucla). With the upper ridge at 500-hPa over the north-eastern continental interior (near Mount Isa, QLD), surface winds veering around to the south (and inland) …near Perth WA, will be forced to rise. The upper trough/ridging combination (SW-NE) can generate a temperature gradient (cooler in the SW) and thus higher wind speeds running NW => SE at 500-hPa, Geraldton to Eucla.

These higher 500-hPa winds can force the surface, warmer, higher dewpoint inland winds (approaching Eucla WA) to interact with the SE edge of the original 500-hPa plume from the westerly belt, leading to convection and/or showers near/off-shore of the SA-WA border area.

Hopefully this will help those on the land smile .

Disclaimer as previous.


Edited by Seira (23/09/2017 22:34)

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#1435200 - 26/09/2017 21:47 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7099
Loc: Adelaide Hills.
Fall of 90 mm record at Denmark (site 9531) almost due west of Albany WA to 9 am this morning (local time). 1-2 m increase in water levels, Denmark River at Mt Lindesay, Kompup and Denmark College. Other falls in the region exceeding 50 mm.

NB: Falls not yet evident along the WA-SA border region, however 1+ mm falls recorded as far east as Eyre WA to 9 am.


Edited by Seira (26/09/2017 21:53)

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