Weather forecasts are flawed

Caught up with this one, at last … and did it over 15 days.

OK - I’ll accept that the topic title is a tad harsh on its own, but not really all that inaccurate when it comes to our needs, either.

No - I’m never going to say “completely disregard forecasts and weather apps/websites”, but I am saying don’t rely upon them alone for making your decisions to fly, or to not fly.
Actual weather reports are always best, and particularly recent actual history to see trends.

Most apps, websites, whatevers are using forecasts that were created hours previously, that had taken ages to process the models that are based on data that was collected some time before that. They are, at best, an indication.
And many of you will have seen posts of mine that are rather dismissive of them - particularly for deciding whether, or not, to go out and fly.

Anyway - the animation below is NOT a weather chart changing from day to day … it’s the changing MSLP (Mean Sea Level Pressure) forecasts for 00:00Z on Sunday 18th of November grabbed at 12 hour intervals from 00:00Z on Friday 2nd November to 12:00Z on Saturday 17th November … ending with a couple of slower switches between the 1st and 31st (last) grab. (Yes - mathematicians will have detected there’s one missing - that changes nothing.)


Now - you don’t have to know a damned thing about MSLP charts, all you need know (as you probably already do) is that these are atmospheric pressure charts, that pressure controls the surface winds and the mixing of air masses - and hence the weather we experience.
(Yes - there is a pressure/jet-stream interaction at much higher altitudes where each is affected by, and affects, the other - but that complication isn’t relevant to this.)

So - for a weather forecast to be accurate, first they have to model the future air pressures (and other factors, at all altitudes, and jet stream speed/location).

This animation shows how successive (every 12 hours) models change for 00:00Z on Sunsday 18th … as to where high and low pressure systems will be, how deep/high they will be, and the pressure gradients in between them, for that particular time in their future.
They eventually begin to change less between successive forecasts as they get closer to 00:00Z on 18th, but do indeed still keep changing right up to 12 hours beforehand.

I’m never going to suggest that weather forecasting is easy - my relatively limited understanding of the process is more than enough to know and appreciate this fact.
But, then again, I’ve not studied the subject in order to become a forecaster, I am not being paid to create these forecasting models, nor am I asking the government for the MASSIVE funds for the constantly updated/replaced biggest computers in the UK that the Met Office has had over the past 50 years to help me do this job. AND this is repeated in countless countries, of course, to provide the data for, and process, the models.

But STILL forecasts are fundamentally flawed and inaccurate and unreliable … as this animation basically shows.

Other than to have a job that still pays me when I get things totally wrong - I’d not have the job … but the whole things really interests my, and I’ve read shit loads over the last 50 years (since I started flying with the RAF) about it as a consequence.

I repeat - don’t IGNORE forecasts. But learn to use the information they provide wisely and always find recent actual weather reports whenever you can. (Airports are the best, IMO.)
Actual weather reports that are 1 hour old are probably near 12 hours more accurate than the best online forecast.
Forecasts don’t take into account a lot of what can impact the wind where we are actually wanting to fly.
Forecasts don’t take account of local topography and the way in which it can funnel wind into, or even shelter, places.

Remember, weather is fickle! Always keep your eyes open to what’s happening around you. That is ALWAYS your best source of weather info.


I just look out of the window Dave :crazy_face::upside_down_face:


So you didn’t actually read the post then. Ah well.

Err… not really, I’d not long been up and there are far to many words at that time in the morning

But you seemed to miss the whole point and just re-quote it …