One feature I miss, keeps me from buying the premium version.
BrassBoss | Premium last edited by
If the premium Version of the app would include forecast in 5min steps for rain in the next hour, like weather Radar but estimated one hour in the future, I would totally buy premium.
Here`s an example, where the missing feature is included
@BrassBoss Hi, the example from WetterOnline does not show forecast, but it shows past precipitation movement. Nevertheless, one hour steps are already included in Premium.
This actually a concept I've always been really interested in. The correct term would be "nowcast", or "extrapolation". Since models tend to be unreliable for precipitation (especially in unstable air-masses) over very short lead times, prediction of such features is actually better served by this technique. It would be really cool to see it in Windy.
BrassBoss | Premium last edited by
@Korina Yes it does. Follow my link. The yellow bar on the Bottom side of the map is an estimation of the future situation in 5min steps. Thats what i meant.
It is more or less the last image of the radar loop which is shown moving in the same direction during 1h30. Wetteronline does not show a real rain forecast: Radar echoes are not changing during the time lapse. A Radar is not able to predict the future weather, even if there are some weather websites which show this type of illusion.
Yes, nowcasting allows to predict rain at a similar scale as the radar does. But it needs high resolution model on a limited area. It is what MeteoSwiss does using COSMO1km:
Here it’s not the same image moving in one direction and it’s pretty accurate.
@idefix37 Extrapolation is one technique used in nowcasting; hi-res modelling is another. It depends on who's doing the nowcasting – it's actually a fairly loose term. So is "forecast" for that matter: if I used radar extrapolation to predict rainfall more accurately than an NWP forecast, is it any less valid because it didn't use a model?
Convective showers are a great example of how limited short-range NWP can be. Modelled showers are stochastically generated, they are quite literally random. (This stochastic approach to convective modelling was the topic of my recently-completed PhD. All modellers do is inject random numbers to get things going.)
The point is that a model knows a certain area will be "showery", so it spins up random showers. But the real showers will not be in the same place. Only the radar can tell you this. That means that extrapolation over very short time scales (0-2 hrs) is more valuable for point precipitation forecasts than a model. The nowcasts are simply creating a "seamless" feel, but I question the value of this approach.
I understand what you mean but frankly I prefer the Swizz approach rather than a basic displacement of the last radar image during 2 hours. I just want to take an example: in mountains, does the radar extrapolation has an interest for predicting a stormy weather due to the orographic effect? The rain will be triggered without the radar being able to « predict » it, while this type of precipitation is usually predicted by hi-res NWP with convective skill. Of course the last radar image is useful to get an idea of the risk of rain for the next 20 minutes and this is just provided by the radar loop.
@idefix37 Sure, I take your point, I don't want to be throwing the baby out with the bath water. I'm generally thinking about non-orographically induced convective precipitation when I talk about the merits of extrapolation. But do bear in mind – models can be pretty bad when it comes to orographically induced convection.
Frontal precipitation is a very different story however, and I would most certainly agree that a high-resolution model will beat extrapolation in a frontal situation over complex terrain even at short lead times. I'm not sure what the Swiss approach specifically is, so I won't comment on that.
With convective showers though, the terrain won't matter as much. The triggering is a bit less random, sure, since the model will understand the thermal properties of the orography to some extent. But terrain induced resolved convection still has a ways to go, especially because of a problem known the "grey zone", which is emerging in sub-kilometre resolution limited-area models.
All the same, if anyone knows their way around complex-terrain NWP, it's the Swiss :)