The 2006 "I have a weather question" thread

Bugski

A Local
Jul 15, 2003
18,937
7
638
Hot Ham
Hello all,

Every year we get questions about how to read charts, what the weather will be like on such and such a date and other miscelleaneous questions. This is the thread for those questions. I'll rarely if ever have the answers as I am a weather newb, but others can usually help.

The other types of threads we usually have here are threads predicting when snow bearing weather will arrive and threads where people make observations about those systems. Please do not put those matters in here.

So post away!
 

snowcrazed

One of Us
Apr 24, 2004
2,978
1
186
38
Aspendale, Vic, Australia
Will there be a 40cm snowfall at Hotham on August 5th for my birthday this year?

(sorry couldnt resist
laugh.gif
)
 
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percy_04

First Runs
Feb 12, 2004
3,676
0
0
32
south aust
no...it will be on August 4th my birthday... it will maily fall as very soft powder....August 5th will be sunny with fresh POWder...
 

percy_04

First Runs
Feb 12, 2004
3,676
0
0
32
south aust
hey mahtoh ive got a questions, what models would you reccomend to help in forecasting, i did it a bit last year and the year before but only went off of the one model which u kno...is plain stupid, im a WZ member and use GFS and LAPS but LAPS only goes 4 days out. what other models are there to help...where can i find them? thanks in advance,

oh and one more thing, i only use the 850hpA map to look at what weather is coming. what other levels would you reccomend? all of them?
 
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snow_hope

Hard Yards
May 23, 2004
383
0
86
35
Sydney
Legit question here:
I use weatherzone and the BOM site, and of course snowatch to check forecasts as well, but are there any other free forecasting / modelling sites which people have found really useful? I remember last season, I think Djon had a great graphical analysis set up (apologies to whosever's it was if I'm wrong here!) but I can't remember the address, and I'm sure there must be other decent resources...
 

Djon

First Runs
Mar 3, 2000
1,301
0
0
Melbourne
Snow Addict said:
djon's - snow.barratt.com.au
snow.barratt.com.au is still there, but is being/has been moved now to :

<a href='http://www.theweatherchaser.com/'>http://www.theweatherchaser.com/</a>

I have recently put up some new GFS forecast charts <a href='http://www.theweatherchaser.com/weather/forecasts/australia/seaus'>here</a> that simply show 1830m temperature, precipitation, and MSLP. 0-180hrs in 6hr increments, updated 2x daily just for South Eastern Australia. These are still being 'worked on' in terms of layout/colours, but it is intended to make it easier to 'read' the GFS forecast to work out if it is going to snow or not. Means you don't need to worry so much about interpreting thickness for instance as an indicator of temperature at a particular elevation.

I am working on some other forecast resources to go up there too which should be operating before the start of the season.

:cheers:
 
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The Frog

Old n' Crusty
Jan 1, 1970
48,171
0
1,386
NSW
What is global warming and how will this affect the snow cover at Selwyn on July 8th at the bottom of the easy does it chair?
 

Taipan

Old n' Crusty
Ski Pass
Jul 5, 2001
33,252
4,763
1,063
NSW Mid North Coast
The Frog said:
What is global warming and how will this affect the snow cover at Selwyn on July 8th at the bottom of the easy does it chair?
Sorry Frog couldnt help myself.

laugh.gif


SATELLITES SHOW OVERALL INCREASES IN ANTARCTIC SEA ICE COVER


seaice1.jpg


While recent studies have shown that on the whole Arctic sea ice has decreased since the late 1970s, satellite records of sea ice around Antarctica reveal an overall increase in the southern hemisphere ice over the same period. Continued decreases or increases could have substantial impacts on polar climates, because sea ice spreads over a vast area, reflects solar radiation away from the Earth’s surface, and insulates the oceans from the atmosphere.

In a study just published in the Annals of Glaciology, Claire Parkinson of NASA’s Goddard Space Flight Center analyzed the length of the sea ice season throughout the Southern Ocean to obtain trends in sea ice coverage. Parkinson examined 21 years (1979-1999) of Antarctic sea ice satellite records and discovered that, on average, the area where southern sea ice seasons have lengthened by at least one day per year is roughly twice as large as the area where sea ice seasons have shortened by at least one day per year. One day per year equals three weeks over the 21-year period.

seaice2.jpg


“You can see with this dataset that what is happening in the Antarctic is not what would be expected from a straightforward global warming scenario, but a much more complicated set of events,†Parkinson said.

The length of the sea ice season in any particular region or area refers to the number of days per year when at least 15 percent of that area is covered by sea ice. Some areas close to the Antarctic continent have sea ice all year long, but a much larger region of the Southern Ocean has sea ice for a smaller portion of the year, and in those regions the length of the sea ice season can vary significantly from one year to another.

To calculate the lengths of the sea ice seasons, Parkinson used satellite data gridded to 25 by 25 kilometer grid cells for the Southern Ocean region. For each grid cell, the satellite data were used to determine the concentration, or percent area, of the sea ice cover. Whenever the percentage was at least 15 percent, the grid cell was considered to have ice. Using this method, Parkinson went through the entire data set and for each grid cell had a computer count how many days of each year had ice, then calculated trends over the 21-year record.

Overall, the area of the Antarctic with trends indicating a lengthening of the sea ice season by at least one day per year was 5.6 million square kilometers (2.16 million square miles), about 60 percent the size of the United States. At the same time, the area with sea ice seasons shortening by at least one day per year was 3 million square kilometers (1.16 million square miles).

Regionally, the Ross Sea, on average, had its sea ice seasons getting longer, while most of the Amundsen Sea and almost the entire Bellingshausen Sea had their sea ice seasons getting shorter.

“The Antarctic sea ice changes match up well with regional temperature changes,†Parkinson said. “The one region in the Antarctic where the temperature records have shown prominent warming over this period is the Antarctic Peninsula, and indeed it’s immediately to the west and east of the Antarctic Peninsula, in the Bellingshausen/Amundsen and western Weddell seas, respectively, that the sea ice seasons have been shortening rather than lengthening.â€

The Arctic also shows a mixed pattern of sea ice trends over the 1979-1999 period, but in contrast to the Antarctic, the area with shortening seasons in the Arctic is far greater than the area with lengthening seasons. The Arctic patterns suggest some connections with major oscillations in large-scale atmospheric pressures, called the Arctic Oscillation and the North Atlantic Oscillation, and it is possible the ice covers of both hemispheres could be influenced by oscillations that are still not fully identified, Parkinson said.

The study used data from NASA’s Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) and the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imagers (SSMIs) and in the future will be extended with data from the National Space Development Agency of Japan's Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) recently launched on board NASA's Aqua satellite.
 
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BrentC

Hard Yards
Jun 8, 2005
428
1
88
34
Victoria
I have a general question regarding what is the Jet stream.
I have very little understanding of what it has to do with the weather (and snow). I know its just a current of fast moving air between warm/cold air masses. My question is - is there an ideal placement of the Jetstream for cold/snowy weather?
I would guess that becuase it represents a boundry between the cold polar air and temperate air masses, then the further north the stream are locateed the better - because we'd have the polar air over souther Australia. Probably wrong though
smile.gif

Also - what happens when the two jetstreams overlap? Is this good?
Cheers!
 
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Undies

Superspreadin the lurve
Ski Pass
May 15, 2002
21,972
17,693
1,063
Top drawer
A few years and a few laptops ago, I had a piece of software that was hooked up to the BOM's various weather stations, and would update every 5mins or so, according to how it was set. It was a little icon in the bottom right of screen, and would constantly show the temp of the weather station I had chosen, next to the clock on my screen. If you clicked on it, it would give you a full read-out of pressure, humidity, etc....

Does anybody know where I can download this from again? I don't recall it being a BOM tool, but it was a long time ago.....

Thanks!
 

thatbuttonsendsit

First Runs
May 14, 2002
72
0
0
Sydney
No probs. Yes it's a neat little program, I first found out about it here ages ago. The copy in my backup was downloaded in May 2003! I used it for some time before upgrading my PC, then, like you, I just didn't get round to putting it back on.
 

Undies

Superspreadin the lurve
Ski Pass
May 15, 2002
21,972
17,693
1,063
Top drawer
It's great. I remember losing hour after hour at work on it whenever a front was approaching.
smile.gif


As the last job I had it in was 2001, it's no wonder I couldn't find it!

On behalf of bosses and bored employees throughout the the forum, I salute you.
 
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BrentC

Hard Yards
Jun 8, 2005
428
1
88
34
Victoria
Just wondering if anyone knows what times the computer models (Like GFS and GASP) are usualy updated? Is it once/twice a day - morning/afternoon?
Thanks!
 

Djon

First Runs
Mar 3, 2000
1,301
0
0
Melbourne
BrentC said:
Just wondering if anyone knows what times the computer models (Like GFS and GASP) are usualy updated? Is it once/twice a day - morning/afternoon?
Thanks!
The main GFS Model runs (00z & 12z) usually finish around 4am, and 4pm our time, but can often run late. Some time after that (probably within an hour) different organisations will create the charts based on it (eg <a href='http://www.weatherzone.com.au/charts/twcGrads.jsp?model=gfs&chart=mslp&hour=-1'>Weatherzone</a>, <a href='http://www.wxmaps.org/pix/aus.fcst.html'>COLA</a>, and <a href='http://www.theweatherchaser.com/weather/forecasts/australia/seaus?hour=24'>www.theweatherchaser.com</a>
smile.gif
etc.). GASP updates twice a day, but I'm not sure when each run finishes exactly, but is approximately early morning, and later afternoon I think.

Edit : Fixed links.
 
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IAB

A Local
Ski Pass
Jun 20, 2005
8,957
9,055
563
The Shire, Sydney
Can someone please remind me of what the 540 line means again. Is it 0C at 1000m?

And is there a 520 line and a 500 line? Does one of these mean 0C at sea level?

Thanks in advance. :woohoo:
 

BrentC

Hard Yards
Jun 8, 2005
428
1
88
34
Victoria
I realise its proabably an impossible question to answer but I'll ask anyway...

(Won't update, click for larger image)

In the above chart, it shows a massive low the south of WA forming. It also shows it developing on the +144 chart. However, Its not shown on the GASP charts.
Now I know GASP and GFS this far out are pretty much just a
laugh.gif
, but, when the model shows such a massive event on one, but not the other - does that usualy mean it has NFI to what is going to happen?
Does it have any substance in this case?
 
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Falls expat

One of Us
Jul 12, 2000
2,922
219
213
London
Intermediate At Best said:
Can someone please remind me of what the 540 line means again. Is it 0C at 1000m?

And is there a 520 line and a 500 line? Does one of these mean 0C at sea level?

Thanks in advance. :woohoo:
The 540 line is the thickness in deca-metres (i.e. 540 = 5400m) of the layer of atmosphere between the 1000mb(hpa) which is near the surface and 500mb(hpa)which is around 18000ft.

Colder air occupies less volume than warmer air so hence a 1000-500mb thickness of 552dm is warmer air than a thickness of 540dm.

In this case the 540 line indicates cold enough air for snow to fall on the Aust Alps.
 
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Falls expat

One of Us
Jul 12, 2000
2,922
219
213
London
Croweater said:
540 line = 1500 metres I think.
smile.gif
No!

540 line is the thickness in deca-metres of roughly the surface to 18000ft. Therefore 540 = 5400m and bears no relation to 1500m in altitude.

540 line just indicates the overall temperature of the atmosphere is cold enough for freezing levels to drop below the height of our ski resorts. See post above.
 
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tomtankman

Addicted
May 12, 2003
264
166
113
42
Sydney
Gday Grant

GASP is one of the worst performing models. I do not know of any meteorologists who use it. Its subsets LAPS and MESOLAPS are far more usefull. The GFS is a far more accurate model but not quite as good as the EC. If the GFS and the EC are both going for a massive low its a pretty good chance. The EC is available on weatherzone silver.
 

tomtankman

Addicted
May 12, 2003
264
166
113
42
Sydney
Gday Falls

I much prefer using 850 temps and height and lapse rates to work out a snow level compared to thickness. What do you think.
 
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