Updated 11th of January 2012:

Note of benefit: Estimates are theoretical with a large margin for error, not actual. Rain rate footage for the event on the 7th of January can be found here:



Written 4th of January 2012:

An analysis of the last two years of daily rainfall observations – 1st of January 2010 to 31st of December 2011 – indicates a difference in the number of days on which 5 mm or more was recorded. Commencing approximately the 12th of May 2010, and 2011, ending the 31st of December respectively, 40 days recorded greater than or equal to 5 mm, whilst for 2011, 26 recorded at or above 5 mm. In contrast, estimates of soil moisture may indicate greater moisture content overall (on average) for 2011, than for 2010 (138 and 123 mm respectively). The peak in soil moisture estimates which occurred during the peak in winter rainfall (and runoff) during 2010 indicates the potential of up to 200 mm present. In 2011, a similar peak did not occur, however estimated moisture levels appear to have maintained (relatively constantly) at between 100 and 150 mm, although mostly closer to 150 mm. In the latter part of 2011, soil moisture estimates began to fall towards 100 mm (from about the 30th of September onwards). The trend of near-constant soil moisture estimates may have, in part, been due to the significant rainfall events of February and March 2011; on Friday the 18th of February, 57.4 mm was recorded, on Tuesday the 8th of March, 58.4 mm. These events alone contributed significantly to soil moisture estimates, if not runoff directly. Direct runoff for 2011 was significantly down on 2010. Long-term stream flow estimates appear to indicate peak winter flow in 2010 may have been up to 3.5 to 4 times the magnitude of flow in 2011. Rainfall observations and trends are also supported by variations in an experimental maximum and minimum temperature dependent latent heat index, which, while highly complex, for the most part seems to reasonably represent probable falls for this area for the given 2-year period.

Update 9th of January 2012:

The local river is slowly but surely drying out. A rain event on the 7th was only slightly enough to contribute to direct runoff, most soaking into the soil in the short period of time it did occur. Heavier falls appear to have been recorded to the south and west. The river water level has receded half to one metre since the last significant rainfall event (>20 mm). The last significant rain event of greater than 20 mm occurred on the 17th of December 2011.

Note 22nd January 2012:

Surface pressure (1006 hPa, 12 noon) is sufficiently high enough, humidity sufficiently low enough (~20%) and temperature rising enough (currently approaching 34 degrees) for conditions to become conducive to significant moisture advection and convective activity. Currently very light winds.

Period end: 25th January after humidity increased. Trace recorded on the 23rd.

Latent heat estimates indicate moderate-to-substantial rainfall for the period starting tomorrow ending approximately 30th-31st (first noted 21st). Precipitable water for the period appears to be increasing substantially, particularly on the 28th and 29th. The temperature appears to increase slightly before falling somewhat by the end of the month.

There were moderate-to-significant falls in the Greater Adelaide Area over the period 28th-31st, and since the 29th when stream flow was thought likely to peak (for the period)…but not in the Woodside area specifically. In fact no rainfall (other than a trace) was recorded locally until the 30th. That is 1 mm fell 30th to 31st.

A precipitable water estimate from an earlier calculation (28th) showed quite a significant difference when compared to GFS, by more than 10 mm (GFS being higher). It could have meant little, being a relatively simply calculation based on vapour pressure and barometric pressure, but then it could have been something.

The temperature dropped to remain in the mid-to-low 20s with west-to-south-westerly winds and a cool change after about the 30th-31st. There was a period prior to the 30th characterised by sporadic thunderstorm activity late in the afternoon into the early evening which tended to fall abruptly (in a deluge) within a period of 30 minutes or less. Conditions were moderately conducive to a thunderstorm event/period, but I believed anything conducive to a significant impact on stream flow was highly unlikely (we’re talking many inches over a longer period of a couple of days). So while there was a chance of an impact to stream levels, this became more remote with each passing day from about the 28th.

I was also somewhat reluctant to revise the above quote to peak on the 30th-31st (defined by the cool change) because the drop in surface pressure to 984 hPa prior to the cool change (correct reading, which is approximately 998 adjusted to mean sea-level) was not synonymous with the sporadic nature of the thunderstorm activity (which appears to have been very localised, as opposed to widespread).

I feel there is now an increased chance March-April 2010 river conditions being reached or exceeded (i.e. severely low flow levels). While there is every possibility this synoptic pattern could be broken within weeks or months, with each passing day without rain, the probability of a robust change in the patterns falls, not linearly, but more non-linearly, as a power function of how long the period is between substantial rain events capable of noticeably changing flow levels.

[Increasing chance] Continues to climb…

[NB: Based on recent analyses, this trend in reducing stream flow levels is dynamic, meaning it could change.]

This system has been looking interesting (28th-29th) for some time. Initial forecasts appeared to indicate larger totals on the 25th-27th, however the atmospheric conditions were not particularly conducive to breaking the increasing chance of severely low flow levels. There appear to be some fine streams of rain through the Mount Lofty Ranges area in general at the moment, but time will tell whether this rain goes beyond mostly soil moisture.

At the current rain rate of about 2 mm/hr, it will likely take perhaps 5-6 days [possibly less, given this is a dynamic system] for rainfall to have a noticeable affect on run off. Some puddles and beginning to form, but I think 3-4 mm/hr or more might be more sufficient (over 2-3 days).

Edit (update):

Having said all that, this rain is very consistent. Rain rate now 3.7 mm/hr.

Rain rate is not yet sufficient for significant change in runoff (stream flow).

Now that we're officially in March and Autumn:

Taken 5.15 pm, 26th of February 2012, looking upstream:



Taken 5.20 pm, 26th of February 2012, Dry Landscape:



Taken 5.15 pm, 26th of February 2012, looking downstream:



Taken ~ 5.30 pm, 26th of February 2012, looking downstream:



…has not change much since.

We now have a week or more with little or no probability of rain fall (BoM).

Hello! I am new in this forum too!I am a new member in this community. I am happy to be here. Thank you!

System note: ~14th-17th March 2012 on Thursday, 8th March.

Written Friday, March 09, 2012 (I think this is worth a mention), updates where indicated:

I believe, at this stage (9/3/2012), there is the possibility (GFS, maybe ACCESSG) for a significant low pressure system to form over Central South Australia circa 14th-16th March (a cut-off low, surrounded by high pressure to the south, low to the north [tropics]), dragging with it moisture from the Southern Ocean. Soil moisture may be up in the southeast [Australia], much drier in the southwest. Significant (+20 mm) falls may be possible in the Adelaide Hills [update (13/3/2012): latest GFS suggests up to 40-45 mm, 14th-15th]. I suspect there will be a change in the weather pattern in general (temperatures specifically, from low-to-mid 30s to low-to-mid 20s) in addition to a change to runoff and pressure (likely a substantial fall based latest GFS – 9th March [backed up 13/3/2012]). Update (13/3/2012): change in soil moisture 0-10 cm may be as much as 50% of current levels [for example: 50% of 0.2 is 0.1 => 0.2 + 0.1 = 0.3].

The reasons for drawing these conclusions are several-fold:

• An extended dry period with little discernible change in river flow (most recent rain fall has evaporated or soaked into the soil – 24.7 mm in a 24-hour period, with patchy falls a few days after).
• Bedrock formations becoming clearly exposed in the riverbed – suggests a higher evaporation rate.
• Very dusty underfoot; top-soil may have lost some structure due to lack of rainfall/biological activity.
• Insufficient evidence of continuation of river flow from groundwater sources, first noted on the 4th of February (at least a month ago).
• Prevailing light/no winds – insufficient moisture advection.
• Temperature (maxima and minima) remaining relatively steady for several days to weeks (the diurnal difference increasing).
• A general absence of moisture in the local catchment system (temperature too high or low, humidity too low, pressure average).
• A relatively moderate pressure for the said dry period – no significant deviation from observed mean conditions (pressure as at 11 am, 12th March 1013 hPa, currently ~1000 hPa, i.e. falling).

I am not going to guarantee that it will rain in the said period, but there appears to be a higher probability of rain falling during that period, at this point (13/3/2012).

Mostly moderate rain ~ 6 pm to 8:40 pm (14th); Pressure down to 990, then up to 993 hPa ~ 8:40 pm; Temperature 17 C. Rainfall: 15.7 mm total.

Still not enough moisture in the catchment to see a noticeable change in surface runoff (apart for more of a green tinge to the paddocks).

Written 18th March 2012:

Multiple events possible: Tuesday evening-night, frontal system; current forecasts temperature 30-31 C early Tuesday afternoon, 17-18 C through to 25th (next Saturday); 15-20 mm (estimate, at the moment). See ACCESS-R, -G, GFS! First front (short-wave) may clip (or jackknife) Fleurieu Peninsula Central Areas. Overnight lows now regularly 4-5 C. 16.6 mm to Friday night. Significant change pressure and specific humidity (18th and update 19th) – with reservations: 20-40 mm (moisture from current Tropical Cyclone Lua (18th)). Second front may be possible in the days after (3-5 mm). May also be a chance of thunderstorms (?) Tuesday night (update 19th).

Higher falls in the southeast: 20-40 mm (mean falls).

Question: is there a pattern shift this week?

[Note: Higher falls on the 14th to west and south-west Fleurieu.]

Yesterday (Monday 19th): Unchanged.
Today (Tuesday 20th): 17-18 C through to this time next week (unchanged). Pressure now ~ 991 (4.40 pm), was 1005, 2.40 pm 19th.

Time will tell .

10 mm overnight Tuesday-Wednesday. Higher falls again to west and south-west (~ 15-22 mm, BoM). 2.7 mm from stream (?) showers yesterday overnight to 12 midday today. No significant affect on runoff (yet).

Post: #862764 - 11-05-2010 03:48 PM:


Pretty much sums up this situation in the riverbed today. Ponds/puddles fast disappearing.

Special Note Written 1st April 2012: Observations

Possible spike in [specific] humidity circa 27th March. Trace on 30th (convective). Pressure may fall in coming days.

Today (2nd) could be interesting. Convective activity already evident.

This is recently, Late March (24th) this year:



This is Early-to-Mid May (11th) 2010:

9th April 2012: Surface-water drying out rapidly. Questioning potential causes. Not obvious .