nowcasting fail

Prediction is very difficult, especially about the future.

— Niels Bohr (attrib)

Or even about the present, it seems.

We have grown more attentive to the weather since installing solar PV.  Knowing when it is going to be sunny for a long period is useful for scheduling clothes- and dish-washing. (Sunny weather used to be “washing day” for hanging clothes out to dry; now it’s washing day for powering the washing machine.  Plus ça change, plus c’est la même chose.)

I gave up on the default weather app that came with my phone long before we installed solar PV, and downloaded BBC Weather instead.  I’ve had my issues with the BBC weather app before, but today was quite extreme.

Here’s what my phone says the forecast is for the town where I live.

today’s weather forecast, as of 7:55GMT

That doesn’t look good: thick cloud at 8am, thinning to light cloud during the mid-morning, thickening again around noon, then rain later.  Okay, not a nice day at all.

Hang on a minute.  Thick cloud at 8am?  But, out the front window it looks like this:

today’s weather, at 7:55GMT

I know weather prediction is supposed to be a hard problem, but getting it so wrong not for the future but now, well, that's another thing.