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Timmead

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Posts posted by Timmead

    Convective / Storm Chat And Discussion

    in Storms & Severe Weather

    Posted

    The cumulative rainfall radar shows that most of the country has seen at least a couple of millimetres of rain in the last 24 hours, with many places having 5mm or more. The only areas that have stayed largely dry are some southern coastal fringes, a small area to the south of the Firth of Forth... and a little area of East Anglia centred on Norwich. :lol:

    Thanks. Probably not enough for the farmers then - though I guess some will be luckier than others

    Better Than The Models ?

    in Spring Weather Discussion

    Posted · Edited by Timmead

    I am always astounded when people speak of the Coriolis Force as though it actually exists. It doesn't.

    The Coriolis Effect certainly exists, and is a consequence of coordinate reference systems moving relative to each other. Imagine a missile fired due north from the equator, remembering that north / south simply means the alignment of a great circle passing through the poles. Now relative to solar system coordinates - however they are defined - the velocity of a missile fired from the equator towards the north pole has also a considerable west-to east component because of the Earth's rotation - which is greatest at the equator and zero at the poles - and this equatorial west to east component becomes increasingly evident as the missile approaches higher latitudes. Put another way, people on the equator are moving through the solar system faster than those in Greenland. For an observer on Earth, it appears that the missile's path assumes an eastward curvature. This is the Coriolis effect. Engineers dealing with the Coriolis effect must correct for the apparent drift if they want to hit the pole, and this correcting force corresponds to what is called the Coriolis force.

    The Coriolis force in fact is a theoretical force used to build mathematical models for correcting courses. There is no real-life Coriolis force, and it astounds me to read explanations of physical phenomena that refer to the Coriolis force. I even heard a load of rubbish being spoken about large tank ships having to correct for the Coriolis force as they cross the oceans. What a load of tosh; if their course is unsteady it is because of directional instability (wrong trim), propeller forces, rudder slightly misaligned, or unequal marine growth on the hull. Or have I misunderstood?

    A bit off topic, but it is a force as far as most physicists are concerned (albeit a "fictitious" one in that it does, as you say, originate from relative rotation of different co-ordinate reference frames), as it must be considered in dynamics calculations in a rotating frame. For example, a stone dropped perfectly vertically from a helicopter at the equator in totally calm conditions will experience the Coriolis force and thus drift slightly eastwards. If you ignored it, experiments wouldn't match your theory. Therefore it is a "real" force

    Evidence Of A Link Between The Moon And Weather ?

    in Space, Science & nature

    Posted · Edited by Timmead

    I'll be surprised if you get a decent PMCC based on that graph of predicted daily temps. However, as I said before, it's probably more interesting to see how well it works over the years, so I'm glad to hear you're going to have a look at past years.

    Admittedly you won't get as much praise for correctly predicting the past as you would the future, but I'll be impressed if anything does show up.

    Edit: The reason I'll be surprised (putting aside my general scepticism of lunar-based prediction) is that its far too regular - I don't see how it would out like that; cold and mild don't alternate in such a way. But I'll hold back any further comments until I see some more data.

    Better Than The Models ?

    in Spring Weather Discussion

    Posted · Edited by Timmead

    cant say as i have ever realy linked the moon cycles to weather

    thinking logicaly about it it makes perfect sense I think all would agree that the sea's pay a large part in our global weather

    all would agree that the earth is 70% + water

    the moons gravity gives us tides all that mass of water moving has got to influence the weather

    i dont know what im getting at but just sharing my thoughts

    I think you mean intuitive rather than logical, in which case I agree. Though obviously things in science are often counter-intuitive, which is why we must use data rather than intuition.

    Evidence Of A Link Between The Moon And Weather ?

    in Space, Science & nature

    Posted

    Yes, and also the direction of extremity - was it colder, or warmer ...

    Indeed.

    Have you thought about analysing the Hadobs precipitation series? If the moon were to play a part, I wonder whether the extremities would extend to other weather observation factors.

    It is certainly interesting to analyse data and try and find something, but I am doubtful of how meaningful it is.

    Here you go ...

    post-5986-0-94149500-1295102142_thumb.pn

    post-5986-0-30828100-1295102148_thumb.pn

    Was the moon closer to us in 1950? ;)

    That's one hell of a large variance

    Evidence Of A Link Between The Moon And Weather ?

    in Space, Science & nature

    Posted · Edited by Timmead

    Well, would you believe it ...

    I've think I might have found evidence of a link between the moon and the weather (particularly temperature) - I know, I know, I nearly fell of my chair, too.

    Here's what I did,

    I got hold of the daily CET temperature records from the HadObs site, and then I transformed the data from the irritating tabular format the MetO use into a format that is easy for databases to process easily (a pivot query) and removed all the -999 records. I calculated the moon-phase for each day using a system of 0..7 where 0 is a new moon, and 4 is a full moon, and calculated for each date in the series.

    etc.

    Would be interesting to see how those graphs look for each year of the record. i.e. how consistent is the correlation across the years.

    Compiling a series for some 300 years is fine for averages and thus making general probabilistic forecasts, but doesn't tell you much about whether it would be useful as a forecasting tool on any given day, since there may be some years where the correlation is atrocious.

    Isolated Frost Presents: Great Britain December 2010 Forecast

    in Spring Weather Discussion

    Posted

    100% = Average local value

    I.E. The av. temp for N England is 5C, the temp for 2010 December is 4C if 80%, 3C if 60%, or 8C is 160%. Same for precip.

    All in all, practically basing this year's December average on the long term one.

    I hope you realise that is not a valid methodology.

    You can only use proportions if you use an absolute scale - for temperature this is the Kelvin scale.

    An example of why using Celsius won't work:

    What's 50% of 0.1C?

    0.05C? No. Its approx -136C (using the absolute Kelvin scale).

    Hopefully you can appreciate that this is not a sensible way to compare temperature anomalies, and is why absolute anomalies are used.

    Winter Forecast Now Online

    in Spring Weather Discussion

    Posted · Edited by Timmead

    Looks like a good forecast to me; a very interesting read. Like the look of below average temperatures in the south east. Hopefully we will get some snow from this cold although the lack of precipitation will probably become quite an issue after a relatively dry summer here in the south.

    Rainfall was actually above average in every one of the MO's regions for this summer - the south had about 105%

    Source: http://www.metoffice...r/averages.html

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