Notable Weather Events Page 46

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15-16th May 2009

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Blocking highs have been a dominant feature for the last 12 month period. But this block managed to deliver a surpirise rainfall that demonstrated beautifully a south westerly style airflow with moisture picked up from oceans, frontal remnants and enhanced by local gulf streams and orographics dropping rains in only very specific areas.

It benefited very few significantly and a good system it was and is not except for those unique areas that fall in the lines of enhancement. The SE ranges and flats for example have done very poorly as can be graphically demosnstrated int he movie below. It is as mentioned the result of yet another blocking high, not of good system flow and interactions that produce good widespread rain.It was however a beautiful example of orographic rainfall enhancement AND importantly the SW gulf stream working in tandem to produce the near 50mm in the higher central hills. A 700 metre range around Parawa if it existed would not have wrung this much moisture from the skies. Location location location.

The movie below shows approximately 24 hours of the rainfall radar. Both the rain shadow, orographic effect and the south west/ gulf stream effect are hugely obvious. Final rainfall map is to the right of the animation

If the movie above does not embed or play in your browser you can download and view it from HERE.

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For the period from above to the following report I had a break from the site and events recording to concentrate on the birth of our new baby. In truth very little of significance happened in the SE ranges. It was generally average to below rainfalls while the city had scored well with good winter rains along with the mid north and west coast. Riverland districts stayed dry and marginal. A few minimal rainfall events occured and many days of strong gale force winds as is the SA winter period prone to delivering.
Now back to it......

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16th August 2009 storms

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August had been a pretty nondescript month to the time of this report. However an approaching vigorous front promised to  change that and deliver an early burst of record high August heat. What it delivered was a fierce couple of days - lightning, hail, torrential rain and howling gales. Synoptic and sat image to the right. Starting on Saturday 15th with some amazing extreme August temps. It rose to a smidge over 21 at my spot which is a local August record for this early in the month. The winds were howling all day gusting to 60-70km/h for 12 hours. A nasty ground drying day.

Approaching was a spring like prefrontal troughline and a vigorous front close behind this. Instability along the troughline kicked up evening altocumulus storm cells and the best SA style lightning bolts started flashing. KI copped a great show early on with a nice little line reaching us in the central districts around midnight and into Sunday. A half decent squall line had actually formed very rapidly in the usual spots over the northern gulf coastline (see radar image below) with very little down south at this stage.
The photographic conditions were extremely difficult. Wind on my hill was so bad I had to set up the camera on the front seat and shoot through the open window. The car was rocking so badly from the wind that the foreground is blurred in every shot. Storm points of instability moving from left to right in front of me so quickly and striking so unpredictably that capturing the bolts was almost impossible. I needed it to be moving at me, but alas it stayed on the difficult course. The wind eventually got the better of me and when rain and small hail arrived I decided to throw it in (around 2am). A nice fairly average little show of the sort that we used to get with fair regularity over spring and summer.

Not much rain initially with 5mm by 9am. At least the temps had dropped to a more normal wintry 7 degrees.

Graph to left showing rapid temp drop with the wind change

 

Sunday 16th saw the odd coldie style cell rocket through with the still savage winds. Late afternoon evening and a decent line of coldies approached with some solid red cores on the radar. This was a WNW airstream and not common for coldies in this stream anymore. Unlike the horrible SW stream which cuts me out of any rainfall from coldies the WNW works well for me and my area. Was not at home when the approaching evening line hit but only about 4km from home. Where I was scored direct, a VERY localised and intense hailstorm enhanced by local topography, the head of a steep gully and the highest hills this far south in SA, along with the strong updraughts and cold air aloft all combined nicely. It started with the normal pea sized stuff that has fallen during the day and very quickly turned into an amazing dumpage of marble sized hail and larger. It was not just a sparse stone drop but a wall of ice falling from the sky. No rain with the stones. The sound under the tin roof of the veranda was intense enough to be actually painful to the ears. It actually smashed some outside all weather heavy duty spotlights and knocked clumps of clay and stone out of an earthen embankment. This continued for a good 30-45 seconds before turning to torrential rainfall and then back to smaller hail. When over hail drifts cm's deep had collected under the verandah and in the drains. Hours later it was still there! It was the largest non summer thunderstorm hail I have seen. When I got home I discovered we had scored a solid downpour of 5mm in a few minutes making 10.5mm for the day and 15.5mm all since midnight. Nice! Some decent hail had obviously fallen home as well which makes rainfall estimation just that - estimation. Some water damage was evident from the downpour along the driveway from blocked drainage channels that could not cope. Winds were still fierce, but slightly lesser than the previous 12 hours.

More showers overnight the 16th bought the rainfall total  to almost 16mm and 21mm system total.

For the complete radar loop of the event See : 128km Radar Loop for Adelaide (Buckland Park), 09:00 15/08/2009 to 23:00 16/08/2009 UTC
A few snippets can be seen below.

		Far left - squall line over northern central SA areas. left - cell that dropped 5mm in just a few minutes
		left - black cored beauty that dropped the amazing hailstorm near meadows (as described above)

 

I did manage to capture a few shots which can be seen in the following gallery (click on the image).

November Heatwave

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This is incredible really when you look at it in the context of the last few years.

Starting almost 2 years ago in march 08 we have an incredible heatwave that smashes all records.

It'll never happen again they scream, 1 in a thousand year event they scream
Then jan/feb 2009 rocks up and what happens. Well bugger me another heatwave of monumental proportions. On the back of the driest spell ON RECORD (for me anyways) Oh, well, er, strewth, its happened again..

hhmm surely not again?

Well.... here we are in NOVEMBER 2009!! and you guessed it - its happening again. The run of extreme temps. Its not just a flow through pattern of hot for a day or 3 then swing cool then hot. Nooooo its just plain hot. Day after day after day. What is of interest (and I stand to be corrected!!) is that all these runs of heat are caused by stagnating blocking weather systems. The machine just grinds to a halt. STOP! "why?" This is my question. Why has this become the dominant pattern? You can count the number of significant events in this part of the state on less than 2 hands in any 12 month period. This is "normal". By my limited years on this planet and limited understanding this current occurrence for the 3rd summer season (I say summer, because its summer folks, spring never happened) in a row is NOT what I understand as "normal". Now my memory is seriously flawed he he, so I may well be wrong, in fact am likely to be so.
However, to me this perpetuation of stagnation and run of sequential extremes one after another is disturbing. Another event like this over the summer period (let alone this is officuially still spring!) and I will be questioning some of my base beliefs on our weather systems.

Some heatwave commentary.

The "heat watch" warning system was activated for SA again.
Water restrictions will remain in force.
It is more than a century since Adelaide had an official heatwave in November. 115 years ago with four consecutive days of temperatures reaching 35 degrees.
On this last point its looking pretty sure that what we are suffering will WIPE the floor with all previous events. As of the 9th the forecast for Adelaide's days was as follows.

Sat 7th max 34.4 min18.6
Sun 8th max 36.7 min 25.4
Mon 9th 37 min 24.5

And the forecast for the week ahead
Wednesday Min 25 Max 39
Thursday Min 25 Max 39
Friday Min 23 Max 39
Saturday Min 22 Max 34
Sunday Min 18 Max 29
Monday Min 15 Max 28

That is extraordinary!

And not in any way good..........

On the 11th the progression read like this....

This is day 4 for the city above 35 degrees. If it follows through then it will make 8 consecutive days above 35. Consider the old record, that 115 years ago it made 4 consecutive days above 35. This event will double the previous recorded data. This is not just a beating of the old record, it smashes it so far it almost seems impossible. It is so FAR removed from even the noted extremes let alone averages that it truly beggars belief.

Now add to this that we have experienced 3 of these boggling events in less that 24 months.
I have to ask, why, how, help!

From a statistical point of view as far as I can tell this should not be happening.

The runs are as follows

My place maximum min
Sat 07/11/2009 29.2 10.6
Sun 08/11/2009 32.1 16.4
Mon 09/11/2009 32.7 19.5
Tue 10/11/2009 33.7 19.4
Wed 11/11/2009 33.6 19.4

Adelaide Maximum Min
Sat 07/11/2009 34.4 18.6
Sun 08/11/2009 36.7 25.4
Mon 09/11/2009 37 24.5
Tue 10/11/2009 38.9 22.9
Wed 11/11/2009 39 23.7

Of Great interest......

I received this very interesting email from site subscriber Janita from Aldgate. Its a fantastic recollection of conditions in the hills. It reads as follows (with her permission)

Just a few thoughts then, on your latest comments.
Not at all scientific, I am sorry, but one kind of notice things sometimes.
The hills seem to always be cool from April to October inclusive.
Leastways, in the last 30 + years I have always used the fire through these
seven months. So, the Adelaide Hills are generally cooler than hot.

I am older, at nearly 60, and I have been wondering seriously the same
thing about these latest heatwaves. I have lived in the hills since 1976.
I remember one day in 1958 it reached 108 F and we were let of school early.

But here in the hills, I remember thinking a couple of years that we barely had
any hot days - one or two at most. Maybe I was at work at the time and missed them.
I remember years with summers when I didn't feel any warm days
before the new year. A heatwave in November?! Cannot remember that.

I can remember other years when it seemed it was constantly raining.
One year in the late 1970s, 1980s, I noted 3 week period of constant drizzle,
and I hadn't been able to get outside at all in any breaks. I vaguely
remember that that was a high rainfall year.

I cannot ever remember a heatwave as bad as the last one.
I have never felt the need to have air-conditioning in the hills, ever, bragging
year after year that at night the hills cool off and we can sleep in peace - but
that last bout of heatwave changed that! It didn't cool overnight. This was a
first in all those decades of living here. Even my posh new fans weren't enough.
It mostly gets unpleasantly stifling around 3 - 4 p.m. in the afternoon but one
just hangs out for sundown and coolth to return.

I was really stunned by that last heatwave you mentioned and thought, (hoped?)
this must have been a rare one-off. I may even have to put in an air-conditioner
if it happens again. Very wow.

November at this point is running a mindblowing 4.3 degrees ABOVE FEBRUARY'S average max!

Some more stats at the end.
the 19th in Adelaide topped an incredible 43 degrees! This is a new November record for Kent Town/West terrace breaking the old 42.7 set in 1962!. WOW! ALL records were whacked out of the ball park.
The BOM released a special statement detailing the event. It can be downlaoded (in PDF) HERE.

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