The Quest For The Perfect ForecastAdded : Sunday at 13:45 Next month, we expect the GFS ► to be replaced by the new FV3 model by NCEP. There has been a little bit of concern over this, especially as the model hasn't been performing too well across parts of the world, including the USA where it was expected to be a major improvement on the current GFS.
The truth is, that when a model gets a major overhaul, then it does take a few months of upgrades and tweaks in order to get it working perfectly. Small bugs in coding are ironed out and errors in data ingest are also corrected.
That said, the way models work will never be perfect. Take a look at the post stamp charts for just T+6 on the GFS ► :-
×View All GFS ► PostStamp Ensembles Images
They all look the same right? Wrong. In fact, take a close look and you'll see tiny differences between the starting conditions of each model run. These are what we call stochastic perturbations. Basically, the models way of saying that the observation data might be wrong, perhaps there are missing values so it tries to fill them in, but even that's a guess.
The obtain the perfect forecast, you would need to accurately obtain the temperature, water vapour and vertical motion of pretty much every millimeter of the atmosphere around the world at trillions of levels in the atmosphere.
Then, if you had a computer powerful enough, run the physics packages on it and hope that the forecast is created before the actual time occurs. After all, what's the point in getting a forecast for tomorrow, when the computer finishes processing it on Thursday?!
Meteorologists know what would create the perfect model, but until technology is there to do it, we will have to use ensembles and perturbations in order to get a decent idea of the weather in a week or two.
But then again, would we want a perfect weather model? Would we want to know exactly what the weather would be like in three weeks time? Sure, the public would, but for meteorologists? Nah, it would make our job boring, we'll take ensembles, perturbations and busted forecasts until then...
METEOROLOGIST : MARSH |