Author Topic: 13 Dec 2008 Stanthorpe NE cell  (Read 5113 times)

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Offline Paul D

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13 Dec 2008 Stanthorpe NE cell
« on: 17 October 2009, 10:26:17 AM »
In mid Dec 2008 I was working NE of Stanthorpe in the Cherry Gully area, about 1/2 way between Stanthorpe and Killarney.

On the 13th of December there was strong although relatively calm, downpour from a rapidly moving cell. As the rain eased there was what sounded like the roar a few Chinook's approaching, this was accompanied by a sudden increase in wind (West to East). The trailing end of the storm was a couple of km's to the south. It appeared very low and moving fast toward the app ESE, the roar appeared to be travelling at the same speed as the back of the storm. The wind further to the south of us appeared to increase in strength appreciably. The closer to the back of the storm you looked the more the trees were being bent over. The main area under the back of the storm was over a ridge to the south, the view of underneath the tail base was obscured by a ridge and precipitation.

The time of the tail passing was app 4:30PM 13th Dec 2008. The track of the back of the storm was app from Old Stanthorpe road over Cherribah resort land toward the border with NSW. Over the next couple of minutes as the storm travelled off the wind eased back to almost calm again.

The reason I though I would post this even though is a bit late is I found my note of the time and date a few days back & I just stumbled across how to get archive radar images of the day.

See : 128km radar

The radar image doesn't appear to show any intense rainfall associated with the system but the rain we encountered was fairly heavy although brief, as the system was moving very rapidly toward the SE.

Although there is no evidence that this system grounded a tornado, the sound from the back of the storm was intense.

The area the tail of the storm crossed is fairly rugged and mostly inaccessible. I haven't found any recent remote sensing imagery of the area, current Google imagery is 4 years old, and in QLD they don't appear to do regular airphoto swaths. In WA you can get detailed online Airphoto imagery through Skyview WA, where you can access (at least in the SW) images which are updated yearly, which is a handy way of checking for suspected tornado damage if you don't have time to do it on the ground.

I've attached a Google Earth image of the app track of the back of the storm +/- a km.

Regards Paul
« Last Edit: 17 October 2009, 01:56:23 PM by Michael Bath »

Offline Paul D

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #1 on: 24 October 2009, 11:11:59 AM »
A bit of extra info
A couple of things which are apparent from the Radar images
1. the main downpour of rain was from a completely different cell that had past just to the south / overhead in the 15-20min prior to the approach of the 2nd cell.
2. the 2nd cell associated with the associated wind past well to the south, and the tail in the trailing NE corner past a lot closer to us with the 4:24 and 4:30 images showing what appears to be a hook.

The winds which I observed to the south I estimated at the time to be up to app 90km/h ( I seen measured constant wind speeds of these values in the last few years in passing TC's) .
My view to the west was completely blocked (We were at the base of an steep east facing ridge) but we had a reasonable view across a low gully and gradual rise to the Sth / SSE.

Below are 3 radar images of the event 4:18 - 4:30
I have marked a cross on the images to highlight my location at the time.

Archived Images sourced from :-TheWeatherChaser.com
Underlying images remain copyright Bureau of Meteorology :- http://www.bom.gov.au
The 128 km Brisbane (Mt Stapylton) Radar Images have been adapted with permission & remain :- copyright Commonwealth of Australia reproduced by permission. :- http://www.ag.gov.au/cca
Paul

Offline Michael Bath

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #2 on: 25 October 2009, 04:17:32 AM »
Hi Paul - I'm surprised the radar shows so little at your location unless the time you report are a bit out?

There is a fast moving cell towards the SE from 0500 UTC - that would be 3pm QLD local time.

Then heavier stuff towards the ENE after 0720 UTC (5.20pm QLD)

The radar overall does not look impressive. The shear was pretty good on the day despite the saturated profile - see Moree sounding which indicates potential for severe gusts at the surface.

Michael


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Contact: Michael Bath

Offline Paul D

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #3 on: 25 October 2009, 07:12:23 AM »
Your dead right Michael I've completely botched the time
I had picked up there was something at odds with the time explanations on The Weather Chaser site but then proceeded to use the AEDT on the images as the EDT he lists as UTC = EDT-10 hours
The Archived images list an AEDT time for QLD images, yet he lists an explanation :-
# UTC is Australian Eastern Summer Time (EST) -11 hours (Daylight Savings).
# UTC is Australian Eastern Daylight Time (EDT) -10 hours

which is a bit at odds with the offical line
Australian Eastern Standard Time (AEST) is UTC + 10 hours
Where daylight saving is being observed: AEST becomes Australian Eastern Daylight Time (AEDT), and clocks are advanced to UTC +11 ( AEDT = Australian Eastern Summer Time)

Now that only leaves clear skys at 06:30 UTC (4:30 PM) I remember noteing the time at the end of the event, and wrote it down as 4:30.
Just a shame I didn't have my cammera and video on me they, were 500m away. The main noise event would have lasted less than 20 seconds
It was definately the 13th of December and may have been 5:30 local time but after the wind event started it was relitively clear at our location and we had a good view of the low trailing tail of the storm to our South which seems a bit at odds with the 5:30 sequence.
Paul


Offline Chris.

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #4 on: 30 November 2009, 04:28:01 AM »
Hi Paul, certainly not trying to dismiss what you heard however the Air Force were practicing maneuvers in and around the storms that month near Stanthopre. Would that explain the noises you heard approaching you?

Regards,
Chris.


Offline Chris.

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #5 on: 30 November 2009, 04:42:53 AM »
I should probably also add that Stanthorpe residents believe the jets were releasing a substance into the storms to suppress hail across the Granite Belt. If this is true or not, I don't know. The Govt dismissed any claims at the time and claimed the Jets were practicing maneuvers around storm cells.

One resident observed several jets around a cell in December 2008 and claims that within minutes the storm dissipated. While the cells do cause Millions of dollars damage across the Granite Belt every season (the most recent 13/11/09 caused half a million dollars damage to one cucumber crop alone) one would think the Govt would have stopped that if at all possible.

I'm starting to get out of my depth here.

Regards,
Chris.

Offline Paul D

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Re: 13 Dec 2008 Stanthorpe NE cell
« Reply #6 on: 30 November 2009, 08:12:30 AM »
Hi Chris
I could understand the Air Force undertaking practice maneuvers around cells. But as for purposes of storm suppression.. I would have to be skeptical.
The particular cell in question though the noise appeared to be in association with what appeared to me to be a fairly intense inflow winds. (Based on recollection only) the noise was loudest (and resonating, hence Chinook analogue) as the winds approached then died off / changed to a constant lower wind roar (not resonating) as they passed..
My thoughts at the time were you would have to be nuts to want to fly in the back of that storm.. I suppose you could never rule it out. but to me it seems highly unlikely due to the timing of the noise and association of intense winds.

I wonder who the locals might have blamed if there had of been any tornadic damage around the time the jets were practising...

I've attached a couple of pics of the 530 radar sequence, 5-30, 5-36 and 6-00 local time
Cheers,
Paul
Seeings I've added an x at my location at the time..

Archived Images sourced from  TheWeatherChaser.com
Underlying images remain copyright Bureau of Meteorology :- http://www.bom.gov.au
The 128 km Brisbane (Mt Stapylton) Radar Images have been adapted with permission & remain :- copyright Commonwealth of Australia reproduced by permission. :- http://www.ag.gov.au/cca
« Last Edit: 30 November 2009, 08:18:15 AM by Paul D »