Victoria: A week of fronts/lows for SE September 21st-24th 2009

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Re: Victoria: A week of fronts/lows for SE September 21st-24th 2009

Post  Power Storm on Thu Sep 24, 2009 5:29 pm

Just noticed that there is quite a substantial cell to my NE, and in the last couple of hours convection has shot up and grown strongly. Maybe an interesting night here...

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Re: Victoria: A week of fronts/lows for SE September 21st-24th 2009

Post  droughtbreaker on Thu Sep 24, 2009 5:30 pm

I'll put my comments in before I go through all the posts from today. Classical spring day today in Melbourne with the 'four seasons in one day' making a welcome return. Mostly cloudy for most of the morning and early afternoon with an absolute ripper of a downpour around 12:00pm that flooded part of Errol Street, everyone had to walk on the road to get around it. I'm sure many parts of inner Melbourne were flooded in parts where there is poorer drainage. Later in the afternoon, sunshine and warm.

2.2mm here but other than 0.6mm at the Melbourne Water Mount Macedon automatic gauge there were no other totals falling over the gauges locally so we must have got lucky. Plenty of puddles around anyway on the way home. 1.7mm yesterday as well so another 3.9mm the past two days which keeps things ticking. There was some very nice cold air Cu/Cb bubbling away towards sunset over the Dandenongs.

As for this weekend. If anything it looks to have upgraded although I'm going purely by GFS here so could be a different story with the other models but hopefully not. Very strong and vigorous SW flow. 850T of -4C and could even reach -6C locally if LAPS is to be believed although I reckon that's a bit over the top. The main thing though is rainfall progs remain very healthy on and south of the ranges to coincide with the cold air with roughly 10-15mm likely here by the looks of things which usually doesn't happen here in SW winds which indicates very vigorous dynamics. Catchments are going to get an absolute drenching with a dumping of snow on the Yarra Ranges and maybe the top of Mount Dandenong.

As for here there is still the chance of some snow at times down to my elevation (520m asl) but more likely 600-700m+. You'd reckon Mt. Macedon would be covered to half way down the mountain by Sunday but I admit I have a habit of getting over excited about things and mozzing them so I'll keep quiet. Rolling Eyes

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Re: Victoria: A week of fronts/lows for SE September 21st-24th 2009

Post  JC on Thu Sep 24, 2009 6:57 pm

hillybilly wrote:
Your working above are not dissimilar to my understanding and I am well aware that your knowledge is far superior.

Johnno the 850 level varies with the surface pressure and the temperature - I took a guess at what the current progs were suggesting. Looking closely the actual level looks to be (about) 1300m at the peak of the cold outbreak over southern Vic.

If you look across southern OZ on Saturday the level ranges from near 1200m over Tasmania to near 1600m over southern WA.

The variation of the levels is a bit of a trap for "young" players. I've seen 850T before to -7 associated with BIG highs coming in behind cold outbreaks. These look furiously cold, but when they are sat at 1700m (rather than ~1300m) they are a pretty unremarkable airmass!

I actually find the thickness values a better guide on most occasions as they measure temperature and are not dependent on surface pressure.

Hi Hillybilly,

I am not Johnno I am afraid, JC stands for Justcruising from WZ.

I always take into account the thickness values and as a rule of thumb this will equal snow at 1400 metres if the 540 line is above the alps.
As a guide 536 will get down to around 1k and 528 will get down to around the 500-700 mark.
Once again the 540 line can even be present as a "doughnut" over the alps within a cold cored high pressure system.
I find it interesting that the '850 level varies with surface pressure and temp' I haven't taken this into account with my analysis.
I know that accurately forecasting snow levels is most certainly a difficult art and topography has a huge impact on what happens in real life. Nevertheless, I still stand by my forecast that snow is certainly a chance or even likely at Mt Macedon and I think the Dandenongs will only see sleet at best.

Anyway enough of that - was probably best for another thread I dunno..

Onto today that was a very photogenic cell or what looked like a series of cells that I saw coming down the eastern freeway at around 2ish today. Very strong updraughts that looked fantastic against the clear blue sky.. Certainly doesn't surprise me that there were some great rain rates observed, the structure was solid and anything but weak...

Now onto tomorrow and this weekend - I can't wait!
My type of weather and it was long missed this disappointing winter...

JC

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Re: Victoria: A week of fronts/lows for SE September 21st-24th 2009

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