The forecast minimum temperature at Coffs Harbour today was 4.1 degrees too high. So what, you might say. But it seems to happen every night. Or at least every cool, clear night, and we've had quite a lot lately. Does the BoM ever learn from its errors?

Very interesting, but you are not the only one, it has been happening in many other locations too, Canberra, Hobart, Armidale etc...
Maybe there is an AGW component but its not working.

No, it's just that there is not enough time spent forecasting the coming weeks weather, rather it is spent on forecasting what the weather will be in 30 years time.

A colleague contacted the BoM on this issue a few days ago, and got a helpful response, including that it had been noted "...that with the last week of calm and generally clear nights some forecast minimum temperatures had significantly large errors in a number of NSW locations. With this sort of change in weather pattern the forecast models can often do poorly and the forecasters do need to be mindful of this when finalising the temperature forecasts."

Interestingly, the last couple of mornings have been much closer: 8/9.0 and 9/8.1

Graham - your colleague highlights why we need to make sure there are experienced forecasters around who can make judgement calls from experience and observation instead of relying on computers.

The forecast errors around Bathurst have been VERY regular the last couple of months.

Yep, things have definitely improved since the matter was brought to the BoM's attention. There is hope for the world.

We've had another prolonged spell of clear weather. And it would appear that forecasters have short memories ...



I couldn't be bothered communicating with the BoM again. It looks to me like the computer models need a tweak.

There can be BIG differences between ridge tops, valleys and coastal locations in winter, making them hard to forecast. Is the Coffs AWS in a hollow? Those forecast minima would probably be close to the mark for somewhere on the coast and/or on a ridge top. Even hollows a stones throw from the coast can record surprisingly cold minima if they are in a sheltered spot, Moruya Airport is a great example.

The Coffs AWS is on a coastal plain about 500 metres from the sea. Ironically, the forecasts have been pretty spot on for my place, on a ridge about 5 km inland. But they're not forecasting for my place, they're forecasting for their place, aren't they?