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#1413157 - 18/03/2017 15:08 Re: Streamflow Observation [Re: Seira]
Seira Offline
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Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
14th to 24th of March, 2017:
Potential Key features:
  • Deep Southern-Ocean rossby-wave slings NE in the Indian Ocean.
  • Rossby-wave, with significantly-lower 500-hPa temperatures (-30s), reaches the NE edge of the Eastern IO high, intersecting the 576-thickness line.
  • WA surface troughing and low activity drifts SW into the ocean, interacting with approaching rossby-wave.
  • The high in the Bight is disrupted by the intersect (having already been disrupted by isoheight anomalies a week earlier).
  • The disrupted high in the Bight moves further east, allowing more southerly air-streams north near its SW corner.
  • The now-shorter-wave upper trough buckles, allowing the 576-thickness temperatures to wrap around it, disconnecting at the surface from the deep-south trough, potentially dragging East-Coast (Coral-Sea) activity west.
  • This potential [cut-off] system is capable of gaining more latent energy from the tropical north (Broome-GOC-NE QLD-NSW), intensifying pressure and temperature gradient at its core, both vertically and horizontally.
  • Flooding is a potential issue (consequence of this) along the NSW northern Coastal Fringes within this time period, as Coral-Sea moisture ventures south.
  • The troposphere, in this situation, would be fairly unstable with cooler-to-colder air above a milder-to-warm, humid air-mass.
  • A second upper trough ventures NE into the Eastern Indian Ocean, this time buckling (because it is stuck between ridges and the first cut-off).
  • This second upper trough also A. disrupts the 576-thickness NW of Perth WA, and B. drags moisture off a developing surface low near Broome, intensifying its development.
  • The 576-thickness (approaching Adelaide) drags much-higher dew-points (+14 C) in an arc from as far as Broome and SE QLD…again.
  • The first shorter-wave cut-off is likely to add to the consequences of the second.


Edited by Seira (18/03/2017 15:11)
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#1413220 - 18/03/2017 20:06 Re: Streamflow Observation [Re: Seira]
Seira Offline
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Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
14th to 24th of March, 2017:
Potential Key features:
  • This potential [cut-off] system is capable of gaining more latent energy from the tropical north (Broome-GOC-NE QLD-NSW), intensifying pressure and temperature gradient at its core, both vertically and horizontally.
  • Flooding is a potential issue (consequence of this) along the NSW northern Coastal Fringes within this time period, as Coral-Sea moisture ventures south.
  • The troposphere, in this situation, would be fairly unstable with cooler-to-colder air above a milder-to-warm, humid air-mass.

More Flood Warnings now issued by Bureau.

Clarity: mesoscale cut-off near Eastern Seaboard is a precursor.


Edited by Seira (18/03/2017 20:16)
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#1415673 - 26/03/2017 00:06 Re: Streamflow Observation [Re: Seira]
Seira Offline
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Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Bowen QLD might need to prepare for flooding next 3-5 days... frown just my view, oh well smile .
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#1415921 - 26/03/2017 13:32 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
Bowen QLD might need to prepare for flooding next 3-5 days... frown just my view, oh well smile .

"Areas of heavy rain with the potential to cause severe flash flooding are expected to develop about parts of the northern and central Queensland coast and adjacent inland areas late on Sunday and continue through Monday and Tuesday."

Source: Bureau.
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#1418996 - 29/03/2017 16:54 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
Originally Posted By: Seira
Bowen QLD might need to prepare for flooding next 3-5 days... frown just my view, oh well smile .

"Areas of heavy rain with the potential to cause severe flash flooding are expected to develop about parts of the northern and central Queensland coast and adjacent inland areas late on Sunday and continue through Monday and Tuesday."

Source: Bureau.

Several streamflow sites now at major flood classification level in the region...some continuing to rise (e.g. Mt Bridget TM, SW of Mackay) frown eek !

[544 mm in 24 hours at Undercliff (533126) TM shocked .]

Source: As above (Bureau).
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#1419028 - 29/03/2017 18:00 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
Several streamflow sites now at major flood classification level in the region...

Warnings issued accordingly.
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#1419549 - 30/03/2017 13:29 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
Originally Posted By: Seira
Several streamflow sites now at major flood classification level in the region...

Warnings issued accordingly.

Warnings Warranted...Situation is becoming decidedly serious with system venturing further south, dumping 100s of mm SW of Brisbane frown , further falls on now already-affected areas!!!

[For anyone reading these notes (in affected areas), I strongly suggest following the Bureau's advices and warnings, observations and stream levels carefully smile .]


Edited by Seira (30/03/2017 13:36)
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#1419907 - 30/03/2017 20:18 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Very significant (major) flooding in the Logan and Albert River Catchments SW of Brisbane shocked frown !!

Source: Bureau warning notes.


Edited by Seira (30/03/2017 20:25)
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#1420833 - 05/04/2017 22:32 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
The following is based on the period 14th to 24th of March (previously indicated), prior to the formation of STC Debbie (about the 27th), which seemed to be associated with Monsoon Trough activity (initially) in the Coral Sea, around the same time. That event has been adequately covered in the appropriate threads, for better or worse.

Written 12.40 pm ACDT, Sunday 19th of March 2017:
Winds potentially from the N-NE. Moisture getting pumped down the Eastern-Seaboard via Coral Sea, across the 576-thickness contour. Meaning it’s crossing from higher-temperature and pressure to lower-temperature and pressure regions = more cloud-cover and less volume to retain moisture in the air. Likely to rain out. Add orographic effects from elevated Great Dividing Range to that and there is a recipe for HP thunderstorms/embedded with showers/rain. With dew-points 14-16 C or more across Central NSW (near-surface temperatures 24-26), not good for regions N-NE of Melbourne. Also, a risk of HP cells east of Adelaide Hills as surface troughing wraps around from the S-SE. 700-hPa RH humidity is higher east of Eastern (Mt. Lofty) Range slopes. Very shallow upper-low south of Adelaide = possible heavy falls (see below).

Potential widespread showers/rain
(supported by Bureau 4-day forecast maps, starting 10 pm, 20th of March).

Observations (Collated 22nd of March, 8.20 pm ACDT), Unless Otherwise Indicated.

Echo Hills Alert, 535085 [QLD]: 96 mm, 24 hours. *
South Lesdale Alert, 544029 [QLD]: 57 mm, 24 hours. *
Bourke [NSW]: 31 mm, 24 hours to 9 am, 20th of March.
Cobar [NSW]: 19 mm, 24 hours to 9 am, 21st of March.
Wanganella Gen. Store [NSW]: 57 mm, 24 hours to 9 am, 22nd of March.
Yarrawonga [VIC]: 11 mm, 24 hours to 9 am, 22nd of March.
Mt. Hotham [VIC]: 33 mm, 24 hours to 9 am, 22nd of March.
Echuca [VIC]: 15 mm, 24 hours to 9 am, 22nd of March.
Kanagulk AWS [VIC]: 25 mm, 24 hours to 9 am, 22nd of March.
Melbourne [VIC]: 9.2 mm, 24 hours to 9 am, 22nd of March, highest southwest (100+ mm) and east.
Portland [VIC]: 31 mm, 24 hours to 9 am, 22nd of March.
Smithton Aero [TAS]: 14 mm, 24 hours to 9 am, 22nd of March.
Mt. Gambier [SA]: 5.8 mm, 24 hours to 9 am, 22nd of March.
Adelaide [SA]: 26.8 mm, 24 hours to 9 am, 21st of March.
Harris Rd [WA]: 70 mm, 24 hours to 9 am, 22nd of March.
Albany [WA]: 17 mm, since 9 am, 22nd of March.

All stated observations contributed to soil moisture or run-off.

* Dates Missing, unable to be checked (rainfall amount known).
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#1421087 - 09/04/2017 11:12 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Melbourne (VIC) may get another 30-50 mm in the next 24-48 hours (to the 11th of April), with a polar-maritime air stream in addition to that already received to 9 am this morning (Melbourne time).
Source: ACCESS-R.


Edited by Seira (09/04/2017 11:15)
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#1421202 - 09/04/2017 23:51 Re: Streamflow Observation [Re: Seira]
Thunderstruck Offline
Lightning man

Registered: 10/05/2001
Posts: 14829
Loc: Seaford Meadows, SA
I read these mate all good!! very impressive wrap around rainband atm, very cold uppers and strong moisture convergence and uplift training in an area for a long time = big flood potential. Convective lines embedded in the main rainband as well adding to the intensity.

TS cool

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#1421305 - 10/04/2017 22:25 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
There doesn't seem to have been any significantly observable/measurable flooding in the area -- according to the flow-meters in the region -- so there is nothing of that to report. There is, however, a stat of 100 mm recorded at Durdidwarrah (site 87021) in the 24 hours to 9 am VIC time, surrounded by widespread 50-99 mm falls to the west of Melbourne...probably contributing significantly to soil moisture.
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#1421604 - 16/04/2017 13:18 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Potential 20-40 mm rainfall event between about the 19th and 21st of April, extending north-south from about 30 degrees South to Mt. Gambier, SA.

[A middle-to-upper level disturbance on the axis of an Indian-Ocean NW moisture in-feed, crossing the 576-thickness contour. Pressure may trough (dip) slightly, late on the 19th.]


Edited by Seira (16/04/2017 13:23)
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#1421871 - 20/04/2017 19:40 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Approximately mid-way through the system (19th-21st), 18-19 mm so far smile .
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#1422003 - 23/04/2017 17:26 Re: Streamflow Observation [Re: Seira]
Seira Offline
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Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Highest 24-hour fall to 9 am 21st of April 2017: 103 mm at Woomelang, VIC; widespread 25-50 mm, Western VIC. Great falls for the Riverina smile !


Edited by Seira (23/04/2017 17:28)
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#1423531 - 17/05/2017 14:38 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Written 22nd of April, 2017, 1 pm ACST:
Another isoheight plume and shorter-wave [modest] upper trough ahead of a front passing through the Bight, this time draw a line from approximately Ceduna to Mt. Gambier with highest falls potentially at each end rather than along the line, and in the north-northeast area (15-20 mm), isolated with embedded thunderstorms: 30-40 mm. 700-hPa RH, winds on ACCESS-R +72 HRS show a north-eastern Indian Ocean in-feed from near [west of] Java, Indonesia. Between a 700-hPa high and low pressure system, being dragged by the extent of the main Southern-Ocean trough system, across Giles-Ngaanyatjarra, towards [east of] the north-eastern flank of the main trough – being blocked on the southerly extent, and drifting southeast as a consequence (passing near Mt. Gambier, SA).

Observations, to 9 am, 25th of April, 2017:
Widespread falls of 25-50+ mm across Southern and Central VIC. Similarly, smaller pockets of 25-49 mm north of Whyalla (slightly more central to SA rather than northeast). One far northeast isolated fall of 26 mm at Kilfera in SW NSW.

Written 25th of April, 2017, 12 pm ACST:
Th axis of the isoheight plume was roughly 90 degrees to the [modest] shorter-wave upper trough that passed through the Bight on the 24th, which makes it aligned SW-NE. This may be enough to disrupt the ridge progressing eastwards, giving the upper trough more movement in the form of a southerly burst (southern and polar maritime winds, higher dewpoints) along the eastern flank of the encroaching higher pressure. This may also increase wind speeds along that edge.

Written 25th of April, 2017, 9.15 pm ACST:
Another [stronger] upper trough with 500-hPa approaching -30 degrees C [1st-2nd of May] in the wake of the one passing over roughly the same region tonight-tomorrow. Second system more focussed around TAS, and near SE Melbourne/Alps.

Potential further falls of 50 to 100 mm, isolated 100+, in a triangle Mt Gambier SA, Omeo VIC, Hobart TAS; increased risk of flooding (now till 2nd of May).

Observations 1st of May 2017, 7.45 pm ACST:
The Bureau’s Australian Rainfall Week Ending 1st of May shows significant falls in an arc from about Portland, VIC, to just across the VIC/NSW border (in Alps). Falls reached the 50 to 100 mm range in this region.

3rd of May, 2017:
No significant changes observed in streamflow gauges: all soil moisture.

---------------------------------------------------------------------------------------------

…15 days later (from the 1st of May).

Written 15th of May, 2017, 9 pm ACST, Grammar Check 16th:
The longer-wave Southern-Ocean middle-to-upper-trough system has now dynamically moved enough (by the Coriolis and Pressure-Gradient Forces) to allow cut-off surface lower-pressure systems to start forming at about the same latitudes as the sub-tropical ridge (about 35 to 40 degrees South). Due to the slighter (weaker) pressure gradients related to the probable formation of these cut-off lows [the air at 500-hPa is 20-22 degrees C], it seems more likely Southern-Ocean moisture on the system’s western rather than eastern flanks would be drawn north towards the continental interior, thus driving – increasing – interior temperature and pressure gradients (on the northern and north-eastern flanks), and therein eventually the eastern flanks.

The northern and north-eastern flanks are likely to be well-connected [in the middle and upper troposphere] due to the west-to-east flow of moisture from the Indian Ocean at those isoheights [e.g. 700-hPa]. Moisture from systems [cut-off lows] further ahead in time steps can feed into a polar- or southern-maritime air stream – the surface ridges would be disrupted enough now to break a blocking pattern. The ridges are more likely to cradle these lows, with an effect of cradling higher-pressure systems…is they allow cold-enough lower-pressure systems to draw moisture from further north-east [the Coral Sea direction]. Accompanied with a surface ridge off the northern QLD coast [directing higher-dewpoint winds east], and orographic effects (the Great Dividing Range to the immediate west of QLD coastal fringes), it is possible, up to 100 mm could fall in an arc [off the eastern flank of the first cut-off system] Townsville and Cunnamulla QLD, Bourke and Mildura NSW, Ouyen and Nhill VIC, Lameroo and Waikerie SA, between approximately Thursday the 18th and Saturday the 20th of May 2017.

As the 500-1000 mb thickness contour is well north of the Southern Ocean (nearer Broome’s latitude), its influence on these dynamics (albeit with the exception of the QLD coastal areas) is limited. If it was further south, say near Alice Spring’s latitude, the temperature and pressure gradients [north-south] may be more substantial, giving atmosphere moisture more opportunity to drift SE across the interior.

Disclaimer: follow at own risk.
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#1424106 - 23/05/2017 21:28 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Originally Posted By: Seira
Written 15th of May, 2017, 9 pm ACST, Grammar Check 16th:
The longer-wave Southern-Ocean middle-to-upper-trough system has now dynamically moved enough (by the Coriolis and Pressure-Gradient Forces) to allow cut-off surface lower-pressure systems to start forming at about the same latitudes as the sub-tropical ridge (about 35 to 40 degrees South). Due to the slighter (weaker) pressure gradients related to the probable formation of these cut-off lows [the air at 500-hPa is 20-22 degrees C], it seems more likely Southern-Ocean moisture on the system’s western rather than eastern flanks would be drawn north towards the continental interior, thus driving – increasing – interior temperature and pressure gradients (on the northern and north-eastern flanks), and therein eventually the eastern flanks.

The northern and north-eastern flanks are likely to be well-connected [in the middle and upper troposphere] due to the west-to-east flow of moisture from the Indian Ocean at those isoheights [e.g. 700-hPa]. Moisture from systems [cut-off lows] further ahead in time steps can feed into a polar- or southern-maritime air stream – the surface ridges would be disrupted enough now to break a blocking pattern. The ridges are more likely to cradle these lows, with an effect of cradling higher-pressure systems…is they allow cold-enough lower-pressure systems to draw moisture from further north-east [the Coral Sea direction]. Accompanied with a surface ridge off the northern QLD coast [directing higher-dewpoint winds east], and orographic effects (the Great Dividing Range to the immediate west of QLD coastal fringes), it is possible, up to 100 mm could fall in an arc [off the eastern flank of the first cut-off system] Townsville and Cunnamulla QLD, Bourke and Mildura NSW, Ouyen and Nhill VIC, Lameroo and Waikerie SA, between approximately Thursday the 18th and Saturday the 20th of May 2017.

As the 500-1000 mb thickness contour is well north of the Southern Ocean (nearer Broome’s latitude), its influence on these dynamics (albeit with the exception of the QLD coastal areas) is limited. If it was further south, say near Alice Spring’s latitude, the temperature and pressure gradients [north-south] may be more substantial, giving atmosphere moisture more opportunity to drift SE across the interior.

Disclaimer: follow at own risk.

Falls exceeding 100 mm near and around Townsville QLD (19th to 9 am) -- Bohle River at Mt Bohle noticeable change in flow. Impact of system extending to NE TAS with falls of 100+ mm near St. Marys (21st to 9 am) -- St Pauls River at Lewis Hill flow change (21st, 73 mm to 9 am). Similar falls north of VIC/NSW Alps along coastal fringes.
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#1424779 - 30/05/2017 22:04 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Written 27th of May, 2017, 3 pm ACST, Checked 28th/30th
The sub-tropical ridge is continuing to push further north into the continental interior as isolation (incoming solar radiation) reduces week-by-week into winter [sunlight intensity per square metre of Earth’s surface], and thus increasing dewpoints and cloud-cover.

It appears the now-diminishing immediate influence of the 540-thickness contour in more southern regions can enable cool-to-cold southerly airstreams (via middle and upper troughs) to clip surface troughs (in ridge gaps).

For this time of year (27th) [around the Adelaide Hills] the temperature appears to be above average; signs of rain would have been well-and-truly on the horizon if we were to go by seasonal averages. Fortunately, front/trough-blocking weather structures such as NW-SE aligned ridges situated in the Bight/Bass Strait are not apparent smile . Thus longer-wave trough features (including isoheight anomalies orientated at the same NW-SE angle) are forming, with consistent attempts by the main long-wave trough to penetrate ridge gaps in the SE. One such attempt seems likely later 29th-30th of May, making it to the Adelaide area. A precursor [system] was also visible on the Sellick’s Hill Radar (on the 27th), with very mild temperatures and a modest upper-trough from the southwest – thunderstorm activity. The isoheight gradient on the system 29th-30th looks to extend towards Geraldton WA, so it is quite pronounced.

There have been two [2] main rain periods recently for the Adelaide area – 22nd and the 28th-30th of May – both from middle and upper troughs. Falls have already reached 30-50 mm in parts of the hills [before the official start to winter]. First potential signs of significant longer-wave middle/upper trough activity [involving the 532-thickness with sleet] for Adelaide-Wollongong-Melbourne in early June (1st-5th).

Disclaimer: see previous post.
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#1425512 - 07/06/2017 20:59 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
Written 30th of May, [Checked 6th-7th of June]:
Coral Sea higher-dewpoint moisture from the north meets [intersects] robust polar/southern maritime air with significant temperature gradient (10 degrees C, NE-SW, horizontally), shrinking tropospheric depth, and potential 540-thickness upper low from the west around the Sydney, Wollongong, Alps Region, circa 7th-8th of June.

A higher-pressure system in Coral Sea [adjacent Brisbane’s latitude] allows moderately warm, higher-dewpoint winds to drift east [along a surface trough running about longitudinally off the coast], reaching Sydney’s latitude. Polar/southern maritime winds in middle/upper troposphere moving [with some speed] north towards Wollongong area, Tuesday. Potential for severe weather north of about Wollongong.

Middle/upper polar winds are -26 to -28 degrees C on ACCESS-G/R (+ 48 HRS/+ 24 HRS); surface winds [from the N-NE along the possible surface trough] are 14 to 16 degrees, possibly 18 [22-24 degrees C], providing some instability [vertically] in addition to Alps uplift. The temperature being lower vertically means the thickness is likely to be lower as well (the troposphere shallower as an upper trough moves east of a strong ridge near Adelaide). This means less room for humidity to be uplifted, and more cloud-formation (air temperatures and dewpoints closer where the Coral Sea surface trough and southerly winds meet). 50-100 mm in the region (1-2 days) – low-lying inundation possible.

Disclaimer: as previous.
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#1426587 - 23/06/2017 22:48 Re: Streamflow Observation [Re: Seira]
Seira Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 6849
Loc: Adelaide Hills.
24 hours to 9 am 23rd of June 2017, SW WA (east of Perth):
Bannister (9507): 105 mm.
Wilgarra (10919): 133 mm.
Wandering (10917): 131 mm.
Widespread 50 to 99 mm through the region.

Significant impact on streamflow levels (near the above sites):
Crossman River at Rivendale,
Hotham River at Marradong Road Br,
14 Mile Brook at Congelin.
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