Tops of clouds?
Thread Starter
Joined: Jul 2006
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From: UK
Tops of clouds?
This may seem a silly question, however I've always wondered if there was a particular way of working out what the top's of the clouds are on a particular day? The base is easily worked out by the temp and dew point, but found it difficult working out what the tops of the clouds would be. Any pointers? if any?
Joined: May 2001
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From: UK
http://www.epa.gov/asmdnerl/CMAQ/ch11.pdf
Of course there are a number of "professional" forecast sources available which do the work for you.
Of course there are a number of "professional" forecast sources available which do the work for you.
Joined: Jun 2003
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From: EuroGA.org
Not an easy area.
The UK Met office does not release its 3D model (except to paying commercial users, a disgraceful tactic IMHO) - the only thing you can get is the standard SigWx form which shows indications of tops if above FL100.
A more recent newcomer is Meteoblue which is a slightly tacky (Java based) site which can do slick looking vertical profiles from (mainly) the U.S. GFS model.
The GFS model itself can be accessed via numerous websites e.g. NOAA but I don't think they have a facility at NOAA to plot tephigrams (a.k.a. ascent or skew-t) which is the presentation that is really needed for easy interpretation.
Historical cloud tops can be found at Univ of Wyoming - these come from actual baloon ascents.
A really good site is Meteox - this carries weather radar and anything red is a sure sign of high tops/CBs. This also carries an archive which shows the weather to be quite patchy on the date of the flight discussed.
If you PM/email me, I have more reading material on this.
None of the tops forecasts are accurate; it's a difficult thing to forecast, but used in combination with other general data e.g. the MSLP charts one can get a pretty good idea.
The UK Met office does not release its 3D model (except to paying commercial users, a disgraceful tactic IMHO) - the only thing you can get is the standard SigWx form which shows indications of tops if above FL100.
A more recent newcomer is Meteoblue which is a slightly tacky (Java based) site which can do slick looking vertical profiles from (mainly) the U.S. GFS model.
The GFS model itself can be accessed via numerous websites e.g. NOAA but I don't think they have a facility at NOAA to plot tephigrams (a.k.a. ascent or skew-t) which is the presentation that is really needed for easy interpretation.
Historical cloud tops can be found at Univ of Wyoming - these come from actual baloon ascents.
A really good site is Meteox - this carries weather radar and anything red is a sure sign of high tops/CBs. This also carries an archive which shows the weather to be quite patchy on the date of the flight discussed.
If you PM/email me, I have more reading material on this.
None of the tops forecasts are accurate; it's a difficult thing to forecast, but used in combination with other general data e.g. the MSLP charts one can get a pretty good idea.
Joined: Aug 2003
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From: Surrey
The USAF has a useful site that also publishes some of the UK met office products Here These give forecast RH at various altitudes so you can deduce probable cloud density. Also, the NOAA site IO referenced does do Skew-Ts. You select a location and then it gives you a page where you can select 'Soundings'. These are forecast soundings and can be displayed as tabular data or as a skew-T (or both)
Joined: Jun 2003
Posts: 13,787
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From: EuroGA.org
Also, the NOAA site IO referenced does do Skew-Ts. You select a location and then it gives you a page where you can select 'Soundings'.
I wonder how the data compares with Meteoblue.
Joined: Mar 2007
Posts: 177
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From: EGNM
When I was taught in my undergrad, we used the rule of thumb that if the difference between the temperature and dewpoint was less than about 2 degrees celsuis in the observed sounding, then you have cloud.
The National Weather Service forecasters I know in the US use infrared satellite imagery and areas of relative humidity greater the 80% in the forecasts to 'suggest' clouds.
Geeks like me who spend all day messing with the numerical models can get these things to spit out concentrations of hydrometeors in the numerical forecasts/analyses, which should be a bit less vague (assuming the models are correct). In the US, the government agencies supply this data to the public e.g. this page: http://www.ral.ucar.edu/weather/model/ but in the UK and Europe the wise government think they can make wads of cash selling this info back to the people who have already paid for it.
Cheers,
Gareth.
The National Weather Service forecasters I know in the US use infrared satellite imagery and areas of relative humidity greater the 80% in the forecasts to 'suggest' clouds.
Geeks like me who spend all day messing with the numerical models can get these things to spit out concentrations of hydrometeors in the numerical forecasts/analyses, which should be a bit less vague (assuming the models are correct). In the US, the government agencies supply this data to the public e.g. this page: http://www.ral.ucar.edu/weather/model/ but in the UK and Europe the wise government think they can make wads of cash selling this info back to the people who have already paid for it.
Cheers,
Gareth.
