Notable Weather Events Page 34

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13th September 2007 front.

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Whats this another front on the way? Spring is here and the weather is speeding up. Quite literally as this system approaches hot on the heels of the last front and rain just a few days prior. The day started windy and warm and the satpic looked pretty darned interesting (see image to the right) Instability was building and the chances of a storm or 2 along the troughline were high The BOM got in on the act in the afternoon issuing a severe thunderstorm warning. SEVERE THUNDERSTORM WARNING for DAMAGING WIND For people in the Lower Eyre Peninsula, Kangaroo Island districts and parts of the Mount Lofty Ranges, Yorke Peninsula, Upper South East and Lower South East districts. Issued at 1:02 pm Thursday, 13 September 2007. A front over southern Spencer Gulf will move across the south of the State this afternoon. Thunderstorms and squally showers with damaging wind gusts are likely in the warning area with and following the front. Locations which may be affected include Port Lincoln, Kingscote, Warooka, Robe and Victor Harbor.

It was rocketting through at light speed and the first arrived in Adelaide early afternoon. A few light showers preceeded the main band and I even heard a solitary rumble at Belair. The main band looked impressive on radar and a bit further north than expected. Nice solid rain began to fall when these amazing echoes from Bucklands park radar were captured.

INTENSE! Should have been absolutely bucketing down wouldn't you think? But in reality it was just solid, steady and certainly NOT heavy rain at all! Bucklands radar was overestimating the falls enourmously. Perhaps Sellicks saw the picture with more accuracy? HOVER OVER THE RADAR IMAGE FOR SNIPPETS FROM SELLICKS AT THE SAME TIME.

By the time the band had passed I had recorded 8.5mm which was amongst the highest recorded for the central hills at this time. A nice total that accumulated steadily over an hour and a half from LIGHT rain, not heavy and certainly not torrential as Bucklands suggested.
Another band was fast approaching. It too delivered nice steady, but light rain down south. However as the line hit the northern suburbs it exploded into an incredibly intense tight squall. This time the radar was not overestimating and is well described by Tim Eckert from valley View
"OMG!!! Amazing stuff!!
5 minutes of the most intense rain for months here!!! Was wathcing radar closely and went outside to greet the incoming line. Could actually hear roar a full 2 minutes before it hit, reaching a stunning crescendo as it arrived!!"
As is so often the case down my way it was nothing more than light rain. Such rainfall intensities I have yet to see in my time at this location, yet they occur with regularity over the northern plains and hills over a 12 month period. It delivered 10mm in 6 minutes at Roseworthy and 10mm in 10 minutes at Forreston. Amazing stuff and very frustrating to watch YET AGAIN the best go north of that line that separates the hills from a heavy rain and storms zone to light rain and drizzle zone. This same line (a strong ranges/gulf/ocean convergence line) is an excellent indicator of where the regular convective storm boundaries lie. North of this and summer convective storms and rain are frequent and often severe. South of this line and the reverse is true.

Anyway, the radar is impressive. See image to the right. By morning I had 16.25mm in the gauge, Meadows town 17mm, Kuitpo AWS 13mm, Kuitpo Valley 18.5mm and as always the best was north with 23mm at Forreston, mostly from the torrential deluge as seen in the radar image to the right.

Meanwhile the Riverland and Mallee scored zilch zippo and dust.

A few spectacular mammatus images were captured by website subscriber Patrick Winnie at Echunga. See the images here here and here.

16th September 2007 , wind, rain and squall.

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Here it comes again! Another fast moving front. Preceeding the front was a rather interesting event in the southern ranges. At 1:45am exactly the wind went from a regular breeze to hammering through at nearly 70km/h. This (windspeed) is not unusual, but from nothing to slam is. The change was instantaneous! It was so sudden and abrupt that it woke us up with rattling gates, windows and roof. The noise of the wind in the big bluegums was deafening. It usually builds to such crescendo's. A nasty gust and sign of things to come. (see graph to right) Interestingly there was a rather significant near 5 degree temperature spike as well peaking at an unusually warm 15.6 degrees. (as warm as the previous days max). This temp maxed out at, yes you guessed it, 1:45am coinciding with the wind slam! Amazing stuff.

Rain was still to come. Most impressive was the squall line developing. The radar looked fantastic!

It held this to the coast and hit with a bang! Bloody hell it was HEAVY! For 5 seconds it reduced visibility as if someone had emptied a truckload of water straight down. Not a lot of actual rain and the WX won't record such intensity, but hells bells. If it lasted 5 minutes it would've made 15-25+mm I reckon. It did drop 4mm in its short burst. Was too fast for a tipping bucket rain gauge on the WX to record. Still got the trusty old nylex for such events! In the city, not protected by frontal hills like my location, severe wind gusts to near 80km/h rammed through, causing minor tree and property damage. The wind turned WSW following the squall and heavy showers followed in the normal streams. On the southern side of the KI rainshadow these rain cells had glaciated tops with almost true "coldie" structure.

Final rain count came in at 8mm for my location, 6mm in Meadows town, 7.2 for Echunga, 9mm for Sth Para and Mt Crawford and 7mm on the south coast. As always, the riverland and some mallee locations missed out yet again.

19th September 2007 localised hail.

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A classic example of a local convergence point was to be seen with the arrival of a front on the afternoon of the 19th. In certain conditions I am left in a dead spot while at a distance that can be measured in mere metres away often torrential rains can be had. In this case more than just rain fell with enough small hail to cover the ground in white. In just a few minutes 6mm of rain was also recorded along with the hail. This tiny spot is indicated on the radar snippets to the right as the red pixels near Meadows township. (top bucklands view, bottom sellicks) I am located just below the town in a "null and dead" zone of light rain and certainly NO hail. I managed just 2.5mm over a long period of time of 90 minutes. Insignificant in comparison, yet just a few hundred metres away, it is bucketting and hailing. Meanwhile just a few hundred metres south of my location its steady to heavy rain, leaving me stuck in the middle. This IS NOT a fluke! It occurs time and time again. Relatively speaking my location just south of Meadows is a "dead zone" where its extremely rare for significant and isolated weather events (such as this small example listed here) occur. As a result of the consistency of this my annual average is much lower than locations just a few hundred metres both north and south of me. This is a dubious honour, one I would rather not have!

September 2007 dry and patchy.

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With just 61mm September 2007 is the driest September for 13 years in my location. Last time it was lower was in in 1994 when we recorded. just 44mm. '94 was even worse than 2007 with just 640mm for the whole year and a VERY dry winter. 1994 is next eclipsed by 1982's woeful total of 470mm.

The lowest September recording for Meadows township is a piddly 22.3mm in 1951. However winter and autumn in this year was quite wet which gave such a low September total minimal impact.

Yes 2007 is a bad year, but it is not the worse. Far from it. What is compounding the problems is that 2007 is hot on the tail of a sequence of bad years ACROSS THE CONTINENT, in particular Southern Australia. Such widespread rainfall deficits have finally seen water resources just about run out from excess population pressure and poor management of what in this country is a fickle resource to begin with.

The current problems are not a climatic aberration or a symptom of "global warming" but a politically induced disaster.
"Grow - grow - grow" they said. Smart weren't they?

Enough politics from me!!!! he he he

Perfect example of the SW moisture Stream.

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Wednesday the 3rd of October 2007 saw a perfect example of "daytime cloud streets" This day saw a daytime SW airstream with just enough moisture to condense the moisture streams into distinct cloud lines while leaving the sky uncluttered. This is vividly demonstrated from the satellite image to the right (streams highlighted). These streams when stronger will often develop strong shower lines. More information on this can be seen at the following pages that describe the Adelaide and surrounds rainfall and cloud streams. RANGES MOISTURE STREAMS

11-10-07 First october rain.

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11 days into October and we see our first rain for the month. A weak westerly change delivers 6.5mm to my location from low based almost stationary drizzle streams. Highest falls were 11mm at Ashton and surrounds with the enhanced orographics. As has become the trend my location was again the odd one out with substantially lower falls than even 2km away where over 8mm was recorded. My spot is in a strange localised rainfall hole which is graphically demonstrated in dam fill failures and noticably lower pasture growth than my near neighbours.

It is worth noting that the previous day (10th) saw significant inland storms with Roxby Downs scoring direct hit from one particular cell that caused localised propery damage. Locally nice convection popped up on and east of the ranges resulting in a few showers and the odd rumble. Nothing significant from this though.

UPDATE.. Follow up rain dropped a further 10mm at my location giving 16.5mm for the event. A reasonable freshner after all.

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