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 Post subject: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 6:16 am 
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Joined: Mon Jan 17, 2011 3:11 pm
Posts: 36
Location: Perth, West Aust.
Weather Station: WH3081
Operating System: Win 7 x64
Hi, been fiddling with my Baro settings as my forecast is constantly saying 'Stormy, Much Precipitauion" all the time and reading the Zambretti forecasting description I noticed that it mentions that the forecast should be calculated at 9am.

Is it a possible to have a setting to do this?


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 Post subject: Re: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 8:01 am 
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Joined: Wed Oct 21, 2009 11:19 am
Posts: 280
Location: Bayswater, Australia
Weather Station: La Crosse WS-2355
Operating System: Windoze 7
You could use Beteljuice's Zambretti algorithm.

I use a php translation which can be run as a Windoze scheduled task.

The php is here:
http://weather.gktnet.com/public/weather/zambretti.php.txt

Beteljuice's javascript is available here:
http://www.dickie.webfusion.co.uk/zambretti/forecast.html

cheers.

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http://weather.gktnet.com/cumulus/index.htm
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 Post subject: Re: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 10:13 am 
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Joined: Mon Jun 02, 2008 6:49 pm
Posts: 17835
Location: Sanday, Orkney
Weather Station: Davis VP2
Operating System: Windows Home Server 2011
The 'stormy, much precipitation' message is nothing to do with the time of day that the Forecast is calculated. Does the full forecast include "Exceptional weather"? Are you sure you have your barometer extremes set correctly? See http://wiki.sandaysoft.com/a/FAQ#My_forecast_always_says_.22Exceptional_Weather.2C_Stormy.2C_much_precipitation.22

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Sanday Weather
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 Post subject: Re: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 1:43 pm 
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Joined: Mon Jan 17, 2011 3:11 pm
Posts: 36
Location: Perth, West Aust.
Weather Station: WH3081
Operating System: Win 7 x64
steve wrote:
Does the full forecast include "Exceptional weather"? Are you sure you have your barometer extremes set correctly?


No, it doesn't include exceptional and I've had the settings the same for a long time, but around xmas when it was damn hot and around 33-39C it would say that all the time.


I know its only for fun, just seemed way out this time...

ANYWAY, when I was doing some research I noticed that
http://www.whitbyweather.com/Zambretti/forecaster.html

says "A forecast made at approximately 09:00 local time is reportedly better than 90% accurate, "

but maybe I read it wrong and they are not saying thats the best time to use the formula and it is less accurate at different times of the day..


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 Post subject: Re: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 2:00 pm 
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Joined: Wed Oct 21, 2009 11:19 am
Posts: 280
Location: Bayswater, Australia
Weather Station: La Crosse WS-2355
Operating System: Windoze 7
Yes, I read that also.
I think that it all gets down to who's got the clearest crystal ball... 8-)

As Steve says, setting barometer extremes is critical. If you set them wrong with Beteljuice's forecaster, the forecasts can be a mile off either way.
I've set cumulus to a few hPa above and below the max. and min. pressure over the last couple of years, but I'm still unclear on what are the best values to use.

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 Post subject: Re: Zambretti Forecast
PostPosted: Fri Dec 30, 2011 3:11 pm 
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Joined: Tue Dec 09, 2008 1:37 pm
Posts: 1888
Location: Dudley, West Midlands, UK
Weather Station: None !
Operating System: XP SP3
Quote:
I've set cumulus to a few hPa above and below the max. and min. pressure over the last couple of years, but I'm still unclear on what are the best values to use.
If the forecasts are (very) inaccurate, then that is the correct approach. (unless of course if some of them are regarded as extreme values - eg. typhoon etc.)
Quote:
No, it doesn't include exceptional and I've had the settings the same for a long time, but around xmas when it was damn hot and around 33-39C it would say that all the time.
If that was exceptional then the forecast is correct, if it 'normal' for your location increase the top of the range a little.
Quote:
Hi, been fiddling with my Baro settings as my forecast is constantly saying 'Stormy, Much Precipitauion" all the time and reading the Zambretti forecasting description I noticed that it mentions that the forecast should be calculated at 9am. ... Is it a possible to have a setting to do this?
Funny, it says that on my site as well :P
Actually it more correctly states "A forecast at approx. 09:00 local Solar Time is allegedly better than 90% accurate ! ".

I think there is already a setting somewhere to use 09:00 ish figures, but then you could lose some unexpected rapid change.

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 Post subject: Re: Zambretti Forecast
PostPosted: Mon Jan 02, 2012 2:47 am 
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Joined: Thu Aug 05, 2010 10:02 pm
Posts: 443
Location: GA, USA
Weather Station: WS2080
Operating System: W7
This is where Cumulus forecast shines. This is a small front moving fast. WU and TV forcast say no rain but Cumulus says:


You do not have the required permissions to view the files attached to this post.

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 Post subject: Re: Zambretti Forecast
PostPosted: Mon Jan 02, 2012 3:39 am 
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Joined: Mon Nov 28, 2011 2:13 am
Posts: 356
Location: Brisbane, Australia
Weather Station: La Crosse WS 2306
Operating System: Windows 7 64 Bit
With my station I am surprised that often it gets it roughly right because adjusting the pressure extremes helped but I don't alway keep an eye on that forecast.

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Web Site: http://www.localweatherdata.0glo.com


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