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#1178153 - 27/02/2013 20:32 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
7 mm soil moisture to 8 pm today since the 25th.

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#1181420 - 07/03/2013 14:07 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Potential for intermittent heavy rain over the next 2-3 days (GFS, Weatherzone, BoM).

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#1181617 - 07/03/2013 19:51 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Potential for intermittent heavy rain over the next 2-3 days (GFS, Weatherzone, BoM).

1 mm in about 1/2 an hour; 0.8 in 2-3 mins (so far).

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#1182943 - 12/03/2013 22:50 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Originally Posted By: -Cosmic- (naz)
Potential for intermittent heavy rain over the next 2-3 days (GFS, Weatherzone, BoM).

1 mm in about 1/2 an hour; 0.8 in 2-3 mins (so far).

Potential ceased 9th March...1.8 mm total.

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#1184652 - 19/03/2013 23:26 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Can just about walk along the middle of the river bed in several sections, including over exposed bedrock. Think that's saying something. Heard it might be the driest March in 19 years (recalled from the News, think it was 7).

As may be commonly enunciated in these circumstances about rain...

"Will believe it when I see it."

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#1184900 - 20/03/2013 22:28 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Based on Bureau's latest forecast for Mount Barker (21/14, Max/Min Thursday March 21st), expecting a sharp change in specific humidity, precipitable water and the diurnal temperature range in the next 24-48 hours.

Last 4 days temps:

21/9, 23/5, 25/5, 30/5.


Edited by -Cosmic- (naz) (20/03/2013 22:30)

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#1185020 - 21/03/2013 11:06 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
13 degrees overnight with ~ 4 mm (soil moisture) from a thunderstorm, possibly more to follow in coming hours/days.


Edited by -Cosmic- (naz) (21/03/2013 11:08)

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#1186304 - 26/03/2013 18:02 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
My Views - Written 23rd, Updated Yesterday (25th), with observations for today:

An interpretation of the likely/past weather conditions, 23rd to the 31st of March 2013 (inclusive):

After a prolonged period of dry conditions in which water levels have dropped to such an extent that (in sections of the river) bedrock is not only exposed, it too is dry or drying…

Streamflow, 24th of March 2013 – Looking Downstream:



…a recent change in weather conditions (starting the 20th of March, 8.1 mm over ~ 3 days) seems to suggest a more robust, rain-bearing change is on the way (or more than one gradually in the coming weeks to a month). This can been seen in both in a consistency of forecasts (mentioned below), and observations. While there is again no guarantee this will happen (in the next few days) it is, as reiterated below, promising smile .

On the following days (24th to 30th March 2013) the Bureau indicated (4:15 pm CDT forecast, 23rd March for Adelaide) that the maximum day-time temperature was expected to increase towards 32 deg C by the 26th, before falling back to the mid-to-low 20s by the 28th. The minimum night-time temperature was expected to increase from the 23rd to peak around 23 deg C on the 27th. The diurnal differences (according to the forecast at the time) were 9, 13, 14, 9, 5, 8 and 8 for the 24th to Saturday the 30th respectively. The maximum daily temperature appeared to be increasing towards the 26th-27th at a greater rate than the increase in daily minimum. While this suggested higher dew points due to correspondingly higher minimums, this could be offset by the change in diurnal range, meaning the maximum temperature was rising rather than falling (i.e. lower humidity); the latter – a fall – likely resulting in both an increase in the dew point and humidity.

The updated diurnal differences (one day on, 24th) of 13 (25th), 17 (26th), 5 (27th), 5 (28th), 8 (29th), 8 (30th), and 10 deg C (31st) indicated a more pronounced change from a difference of 17 deg C to 5, 26th to 27th. If the maximum temperature was to fall at a slower rate (23rd to 27th) than the minimum, this may mean less chance of rain than if the diurnal difference itself simply reduced (i.e. the day-time maximum approached the previous minimum), which now seems to be more likely (as of the 24th).

The likelihood of solid rain is increased by (according to Weatherzone; ACCESS G, GFS, ACCESS R, + 72HRS, runs for 23rd, 24th and +48 HRS for 25th) a robust change in pressure – forming pre-frontal trough and low – and a change in the 500-1000 millibar thickness associated with the temperature. In this situation, as the pressure changes about a day out from rain (currently 998 Sfc. P, 31% RH @ 3:30 pm, 26th) (first increasing slightly then falling sharply) the humidity falls sharply, meaning the specific humidity also falls. As the trough approaches, this gradient (in specific humidity) reverses, sharply, as the humidity increases as the pressure falls.

As indicated by the change in the diurnal temperature range, it increases and then decreases – the dew point increasing, as the humidity falls towards the 26th-27th. For the precipitable water to be impacted, the change in specific humidity needs to reverse in such a way that supports the advection of moisture (possibly a northwest in-feed), which a drop in pressure may assist (i.e. convection and moderated temperatures and dew points over land). Assuming an accompanying front or low (behind the trough), this would bring a change in temperature and thickness.

With an increase in atmospheric moisture supported by a change in specific humidity, dew point and a pressure trough, that moisture needs a trigger to fall out of the sky – a change in temperature. How long it will rain for would likely depend very much not just on how much moisture is in the air, but on how long it can be sustained for. According to the Bureau’s chances of rain (27th), there is at least 90% chance of 1 mm (over Central Districts), grading to 50% chance of 5 mm, 25% chance of 10mm, and 10% chance of 15 mm (update: 10% of 15 mm, 25% to 10 mm). Based on this alone we may not expect much, however the consistency of the ACCESS-G, R and GFS forecasts for the last 3 days suggests it might be somewhat higher.

The expected change in both the temperature and the pressure support the Weatherzone forecast (for tomorrow, 26th) of increasing winds and wind speeds (more so in the afternoon).

This is just my view based on recent dynamics:
I believe this may mean 15-20 mm (locally), possibly 20-35 (localised), if the forecast does not change much in the next day or two. I think that might be bit conservative given the expected/forecast temperature gradient 26th-28th.

There may have been a slight chance of light rain today (25th), due to the aforementioned moderation of temperatures and dew points over land (already somewhat apparent, 25th), preceding the upward temperature change. Temperatures since the 30 degrees recorded on the 20th have not been higher (and no higher than 30 since the 12th), so the (update: 34 deg, Mount Barker) forecast for tomorrow (26th), may break another run of temperatures below 30 degrees.

In practice conditions and variations need to support the chance of this (26th-onwards) happening more than not, and the signs definitely seem encouraging for that period smile .

…26th: 33/9, Max/Min. Increasing winds and wind speeds..

Waiting for (what’s left of) stream water levels to increase substantially...


Edited by -Cosmic- (naz) (26/03/2013 18:09)

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#1186764 - 29/03/2013 12:34 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The minimum temperature overnight 26th-27th rose from 9 and 21 deg C, while the maximum dropped from 33 to 23. This could have meant that while the rain band had higher moisture content, the temperature gradient did not favour significant falls because the minimum rose substantially rather than moderately (say 9 to 16) => reality was 33 – 23 = 10 and 9 – 21 = –12, rather than 10 and –7. A possible interpretation of this is the minimum rising so much meant the pressure on precipitable water to rain out was not there.

The last time the overnight low equaled or exceeded 20 was 51 days ago from the 27th.

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#1186902 - 30/03/2013 11:00 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Fall in (max, min) temperature 27th-28th – rainfall in parts of the hills.
(http://www.bom.gov.au/cgi-bin/wrap_fwo.pl?IDS60160.html)
Note link will update.


Edited by -Cosmic- (naz) (30/03/2013 11:02)

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#1187899 - 05/04/2013 12:35 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
The observations of the opening post of this thread could be at risk of being exceeded (in record-breaking terms) if conditions continue the way they are for another 1-2 months.

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#1189108 - 12/04/2013 13:59 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Type "Percent Rank Relative Soil Moisture (Upper Layer)" or "Percent Rank Relative Soil Moisture (Lower Layer)" in Google to find recent maps for all of Australia smile .

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#1189902 - 17/04/2013 12:43 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Threshold of dry river conditions equalled or exceeded circa 17th April 2013 (observational equivalent of 11th May 2010).

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#1193423 - 11/05/2013 10:38 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Streamflow may be moderately impacted in the next few days.

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#1193992 - 15/05/2013 11:28 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Streamflow may be moderately impacted in the next few days.

Definitely not.

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#1194451 - 17/05/2013 23:35 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Originally Posted By: -Cosmic- (naz)
Originally Posted By: -Cosmic- (naz)
Streamflow may be moderately impacted in the next few days.

Definitely not.

22.8 mm total 11th to 16th May 2013.

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#1194453 - 18/05/2013 00:17 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Correction to last post +2.

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#1194501 - 18/05/2013 16:42 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Written 17th of May 2013 at 11.15 pm CST:

Reference #1189902:
Obs, 11:15 pm, 17th May 2013: Currently 75% relative humidity, 1016 hPa surface pressure and 1 deg C (also the overnight low, 17th-18th). Streamflow water level slightly above threshold.

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#1195112 - 22/05/2013 15:38 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
Continuation from previous reference – conditions now more conducive to substantial falls.

Temperature was 12 deg C today (currently 11). Overnight low of 9; humidity now 79-80% (at/above rainfall threshold), pressure 1001 hPa (~ 1010 MSL). Steady rain/drizzle for 2.5 hours (3 pm CST). Potential thunderstorms/probable scattered showers in the next 24-48 hours (BoM, WZ, ACCESS-R). Potential for water level to be slightly-to-moderately affected by the 24th if current forecast(s) (as of 3 pm CST) holds or upgrades.

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#1195322 - 23/05/2013 13:57 Re: Streamflow Observations [Re: Seina]
Seina Offline
Meteorological Motor Mouth

Registered: 27/08/2003
Posts: 7770
Loc: Adelaide Hills
System track was not as thought.

14.2 mm to 9 am today since midday 21st. Very slight to slight change in water level - little or no runoff.


Edited by -Cosmic- (naz) (23/05/2013 13:58)

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