Sometimes planes leave contrails, and sometimes they don’t.  It depends on the weather, and specifically it depends on the weather at altitude.  It’s also very localized.  A plane might leave a trail in one region, and another plane a mile away might not leave a trail.

NASA have put together a contrail forecast page that you can use to roughly predict when contrails are likely for a given region, and a given altitude.  The following image should be the latest forecast

I suggest also looking at a water vapor satellite image.

http://www.weather.gov/satellite#wv

The presence of a circle at a particular point simply tells you if the conditions are favorable for contrail formation at the altitude indicated by the color of the circle.  The size of the circle only varies so different altitudes can be shown at the same point, but the smaller the circle, the higher the altitude.

The Mb scale on the left is the measure of atmospheric pressure in millibars.  This can roughly be translated to altitude, as pressure decreases fairly uniformly with altitude.  Planes actually use the air pressure to measure their altitude using an altimeter, but you have to set it to the local sea level pressure in order to get an accurate result for landing and take-off.  To avoid confusion, planes flying above 18,000 feet all set their altimeters to the same reference, 29.92 inchs of mercury, or 1013.25mb (for sea level).

The scale starts at 400mb, which is around 23,500 feet, and goes to 125mb, or about 48,500 feet.

The page describes how this works, and I repeat it here in full:

The RUC model data are representations of the complete 3-dimensional structure of wind, temperature, and humidity over the USA at a resolution of 25 mb and 40 km. The horizontal resolution has been degraded to 1° latitude x 1° longitude to facilitate the computations. Because they are based on a sparse number of actual in situ (balloon sonde) data taken every 12 hours and satellite measurements, the RUC data are not a perfect representation of the various meteorological parameters, especially water vapor. The model humidity at upper levels of the atmosphere is often too low, reflecting the current biases known to exist in our measurement system. Persistent contrails require a relative humidity with respect to ice (RHI) that exceeds 100%. We know that contrails are sometimes observed in areas where estimates of the RHI are less than 100%. The existence of contrails in those locations highlights the “dry-bias” in the humidity fields.

Because the input data do not perfectly characterize the meteorological conditions, the diagnoses of persistent contrail conditions are only estimates and will not detect all of the areas where persistent contrails will form and may also add areas of formation that do not exist. All estimates of persistent contrail formation conditions are based on a modified Appleman curve using three different engine propulsion efficiencies. To give some idea of where contrails may form, but are not diagnosed, we have included information about RHI for values above 70% for single-level plots.

Two forms of results are presented.

  1. Favorable contrail conditions, for a range of pressure levels between 125 and 400 mb, are represented as concentric circles – color coded with reducing diameter for each level. These results can be displayed for engine efficiencies of 0.2, 0.3, and 0.4.
  • Favorable contrail conditions at each level, represented by ‘X’, along with relative humidity w.r.t ice (RHI). These results are only available for engine efficiencies of 0.3.

  38 Responses to “Contrail Forecast”

  • Just wanted to comment to regular readers that this is a new page. NASA’s contrail forecasting page does not show up well in search results, as Google links to an out-dated page. This should help get the info out to interested parties.

  • I once saw a very high plane leaving a contrail that lasted for a while, one just below it that made no contrail, and one below that making a short contrail. If chemtrails were true, why would they be spraying at certain altitudes? What kind of bologna is that?

  • I’m not sure what your point is there Nick, but you might want to read this, as it relates to your observation:

    http://contrailscience.com/why-do-some-planes-leave-long-trails-but-others-dont/

  • Wow. Once again, Uncinus, thank you for this site. I’ll be trying to send some old pals over here again.

    BTW, it is “contrail season” in Seattle right now, and I still hope to upload a video to YouTube shortly showing the cumulus clouds traveling below the high cirrus. I did not have any idea how far up those high cirrus clouds were until very recently.

    Lot’s on persistent contrails here, hope to get some things on video shortly that should help explain contrails, and thank you again for this stellar site.

    J.D.

  • Using this contrail prediction map on days when little contrail formation is forecast seems to silence these chemtrail enthusiasts. When they see no trails, it seems to upset their paranoid minds.

    On videos like “What in the World are They Spraying ? ” this tactic appears to be very effective.
    Ernie Lee, BSc Chemistry

  • Radar for “predicted contrail” on Jan 1st 2012 http://www-angler.larc.nasa.gov/cgi-bin/site/showdoc?docid=33&cmd=forecast

    Another Satellite view on Jan 1st 2012 http://ge.ssec.wisc.edu/modis-today/index.php?satellite=t1&product=true_color&date=2012_01_01_001&overlay_sector=false&overlay_state=true&overlay_coastline=false&sector=USA4&resolution=250m

    The Radar map shows “no” predicted” contrail formation as the conditions aren’t right. The other shows contrails in that area…. I have many more examples of the same where the NASA radar that predicts contrails show not possible and the othe other satellite from MODIS showing in fact contrails are where the conditions aren’t right. Seems either the NASA predicted radar is useless or they are spraying b/c the conditons aren’t right?

  • FYI… The location for the contrail/chemtrial is below PA and above WV… If you need more examples to show the NASA “predicted contrails” do not match where the contrails are actually forming, let me know.

  • Like any weather forecast, it’s just not 100% accurate. They have a pretty clear disclaimer on their page: (click the “more..” to read it)

    Because the input data do not perfectly characterize the meteorological conditions, the diagnoses of persistent contrail conditions are only estimates and will not detect all of the areas where persistent contrails will form and may also add areas of formation that do not exist.

    So you will always be able to find examples where it is wrong. The question is: how often is it right?

    Looking at the animation for Jan 1, there seem to be occasional contrail condition popping up all of the country for short periods of time.

    Note the time on the forecast is UTC, that would be Eastern +5

  • Thanks!

  • @jugg

    In the satellite images, there is a large overcast area west of the contrails. If you compared the Terra image taken at 16:25 UTC with the Aqua image taken at 18:00 UTC, you would see that this wet area were moving eastward. That is, the contrails formed in front of the incoming wet air mass, just in the right conditions for them.

    As for the NASA forcast, it probably was made 12 to 24 hours in advance and did not predicted the time and direction of this weather front movement accurately enough. It predicted probability of contrails in this general area but at a later time, 21:00 UTC.

  • Based on the map, the Las Vegas area has unfavorable conditions yet here they are again just west. We’ve have been getting sprayed like bugs for the past couple weeks.

  • “We have” – sorry, typo…..

  • Bugs usually die when sprayed. You are still very much alive.

  • Based on the map for 12 April I see now almost all of Nevada is suitable at atmospheric altitude pressures from 275 or 300-375mb – which corresponds to roughly 18-24,000, or perhaps 26,000 feet for the 275 figure – interpolated by eye from http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html

    Las Vegas doesn’t have conditions directly overhead, but they are certainly there just to the west, down to maybe 250mb which might be 27-28,000 feet.

    From that I’d guess you don’t know how to read the map.

  • Today’s forecast for Northern CA shows a lot of contrails, but we can’t see any because there is a 100% cloud cover with snow and rain. I don’t know what the elevation of the cloud layer is. Are the contrails higher, where the conspiracy theorists will be blissfully unaware, or is this a glitch in the forecast?

  • There are probably contrails well above the overcast. If the theorists could see all the contrails above or often mixed in with cloud layers they would be forced to drop the climate manipulation theories. What would they have left?

  • The tragic thing is that no matter how you TRY to explain the REAL SCIENCE about this chemtrail nonsense, these nut job fanatics are saying that ALL these websites are UNDER “THERE CONTROL”. the government or whatever black op operation that wants to sidetrack the “TRUTH”.
    These highly under educated people are easily manipulated by the conspiracy whacko’s.
    The weak are easier to control via the internet. Get em to believe what you want em to believe with B/S science yeah, internet….. You will never get them to understand….

  • Here in Tucson there is a small group that goes around town posting signs on telephone poles saying LOOK UP AND SEE WHAT THERE SPRAYING and tell you to GOOGLE chemtrails and view a movie.
    These losers even do demonstrations on street corners waving signs and all. They are easy to follow as they post there rallies and theories here on CraigsList…So EASY to mess with……LoL.

    Everytime it’s cloudy here in Tucson the idiots will say looks like they were spraying again!
    When you ask anyone of these moron’s what is it there spraying, who is spraying and why they clueless and tell you to google it and learn….Heck, they don’t even have a clue, they just repeat what they are brainwashed into believing.

    Now, if there is DUST on the cars here it is there PROOF that they were spraying again…Never mind we are LIVING in the DESERT!

    They are spraying to KILL the PLANTS, Spraying to CONTROL OVER POPULATION, Spraying to change the climate, Spraying to poison the water supply to cause cancer, Spraying radioactivity, low levels to weaken the human immune system and the best one I heard was to suck out the moisture from the air to create droughts and severe weather down the line.

    They, whoever you want to believe is they is also totally controlling the news media and FORBIDS them from reporting any aspect of the chemtrails story!!!

    Site I send them…..http://conspiracies.skepticproject.com/articles/chemtrails/#wtf_are_chemtrails

  • I’m sorry folks… I’ve read your “science” and “explanations” but all said and done there is little to no consistency to when and where the “contrails” are appearing. I am an observation first person and when I see with my own eyes the inconsistent behavior of the trails and where they appear I can’t help but think the numbers and your “proof” don’t add up. My uneducated questions follow these lines of thought.. 1.) why are these commercial airliners flying directly over metropolitan areas? 2.) Even on days that there are light to no contrails the air traffic is not the same as the previous weeks air traffic 3.) If these are natural reaction to airplanes in the atmosphere why is it ok to block out the sun with the trails? Dont we all have a right to have clean skies and access to important sunlight?
    4.) I have seen dozens planes start trails just over the city where I live and not stop them until they are on the other side of the city.. these trails NEVER start way out west and come into town .. they are all beginning at the western edge of the metro and usually are sprayed outside the metro IF the wind is blowing steadily toward populated areas…

    I also don’t appreciate the vitriolic name calling when someone questions the validity of whats in our air … if the first response to someone questioning them is to berate them and call them whackos then nothing will ever get done in a cordial intelligent manner. Just because some of you were “indoctrinated” into the scientific world through a state college doesnt make you any better than anyone else. It just makes you the person who paid more $ to be part of the program.

    I remember Americans standing up for the Nazis before we went to world war 2 and even a large % of Americans didnt want a revolution. Before then the Scientists wer sure the world was flat and if you didnt believe the same you could be killed.

    Why did the UN make aerosol spraying to modify weather illegal in the 70′s?

  • 1.) why are these commercial airliners flying directly over metropolitan areas?

    Because lots of air routes go directly over metropolitan areas – airports usually have navigation beacons of various types, and cities are easy refernce points.

    2.) Even on days that there are light to no contrails the air traffic is not the same as the previous weeks air traffic

    What is the question here?

    3.) If these are natural reaction to airplanes in the atmosphere why is it ok to block out the sun with the trails? Dont we all have a right to have clean skies and access to important sunlight?

    Pretty much irrelevant to whether there are “chemtrails” or not.

    contrails usually blot out very little sunlight worldwide – any look at satellite photos of the earth show a great deal of “clear sky”, and “normal pollution” is probably a lot worse.

    Eg have a look at http://lance-modis.eosdis.nasa.gov/imagery/subsets/?area=na & click around North America

    4.) I have seen dozens planes start trails just over the city where I live and not stop them until they are on the other side of the city.. these trails NEVER start way out west and come into town .. they are all beginning at the western edge of the metro and usually are sprayed outside the metro IF the wind is blowing steadily toward populated areas…

    What is the question here?? If you live in a town then it seems pretty normal that you will see contrails over your town. And it may be that the local high altitude air routes do only go 1 way in your area – I don’t know – but you can look them up – http://skyvector.com/ – click on the “Charts” menu and select where you love (if you are in the USA) & check out various types of routes.

  • http://en.wikipedia.org/wiki/Trimethylaluminium

    WHAT IS TRIMETHYLALUMINUM?
    Trimethylaluminium is the chemical compound with the… formula Al2(CH3)6, abbreviated as Al2Me6, (AlMe3)2 or the abbreviation TMA. This pyrophoric, colorless liquid is an industrially importantorganoaluminium compound. It evolves white smoke (aluminium oxides) when the vapor is released into the air.

    MATERIAL DATA SAFETY SHEET for Trimethylaluminum Source Source
    - TMA is a colorless liquid which is pyrophoric (capable of igniting spontaneously in air )
    - TMA is a combination of hydrocabons that closely resembles gasoline.
    - TMA is used in weather sounding rockets where the white smoke provides a “tracer” for scientists to determine wind directions it various altitudes above ground level.
    - TMA Decomposes into Carbon Dioxide, Carbon Monoxide and Aluminum Oxide dust (nanoparticles)

  • TMA is actually almost entirely harmless to spray into the air, as it reacts violently with oxygen, so burns up almost immediately into aluminum oxide.

    Of course nobody is actually spraying it. It was used in the recent NASA ATREX five rocket launch into the upper atmosphere, as a visual tracer. Essentially a firework.

    It’s not used as a fuel additive either, at least not in any conventional jet engines. Even if it was, it would be quite safe after exiting the engine (although incredibly dangerous before that).

  • This site is bs how can you not believe that airplanes are dumping tons of aluminum nanoparticles in our atmosphere when all you have to do is lookup and see it with your own too eyes something is definitely going on…..wake up and stop trying to dumb people down!!!

  • Can you point out which bit is BS, and I’ll correct it. Thanks.

  • You’ve got aluminium measurement capability in your eyes?

    Impressive.

  • dumb people down

    too eyes

    Good one. I suppose you could blame the aluminium.

  • Today is September 26, 2012 and the NASA image/forecast that you posted in your article is dated 01 MAY 2012.

    Do you know of any other contrail forecasting websites?

  • No. I’ll ask NASA and see if they are going to fix it.

  • NASA says:

    It looks like the switch from RUC model data to RAPS have halted our production of the contrail forecast. We need to change our code to work with the new model data and can expect it to be implemented within the next two weeks. We will keep you posted.

  • I just wanted to thank you for some scientific information that actually makes sense. Ive been searching for some logic and truth to the “Chemtrail” bs, and found this site. Thanks for taking the time to speak reason to the reasonable.

  • Uncinus,
    Referencing your reply to a question on 26 ept 2012 at 6:03 PM.

    Can you please update your answer on this page. Thank You, T.

  • Not sure what you are asking Tom, but as far as I know the NASA page is still down.

  • [...] that weather data is never completely up-to-the-minute and accurate. For instance, as explained at Contrail Science, it is basically impossible to measure humidity in a specific part of the sky at a specific [...]

  • [...] that weather data is never completely up-to-the-minute and accurate. For instance, as explained at Contrail Science, it is basically impossible to measure humidity in a specific part of the sky at a specific [...]

  • Thank you Mick very good explanations supported with lots of scientific information, not like “chemtrails” people using You Tube and home made videos
    Keep up good work
    Branko

  • When will you be up and running again? The last image is from April 16, 2013.

  • Mark, At the site where those images are made, there is this notice:
    http://www-angler.larc.nasa.gov/cgi-bin/site/showdoc?docid=33&cmd=forecast

    Important!
    We are currently converting our input data source from the RUC model to the RAPS model. During this conversion, we are only able to present results until May 1, 2012. We are working on the conversion and intend to have this tool working as soon as possible.

    Note the dates! I think we are luck there is anything at all!

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