Why Does The BBC Understate Temperatures?

[cyclonic happiness]

Seems ludicrous to me. The state the temperature will be 4-5'c and it end up just scraping over 1'c in the middle of town?

 

I've noticed this lack of wanting to acknowledge lower temperature creeping in over the last 10 years or so.

 

But some industries like Horticulture and farming, rely on accurate forecasts to know when to sow, or when to cover up crops etc, it makes the difference between me spending one and half hours fleecing the nursery, or not having to.

 

I just think that if the temperature 'could' go down to say -1'c they down't show it as 5-6'c ("and in rural areas it will be much colder")   

 

Just put the lowest and the highest temps that could happen....what's the big deal!  ><

[Guest]

I wonder if this may be because the forecasts are for a general area or region but so often micro climates can make quite a difference - in the case of fruit growers worried about the effects of frost I would imagine that many would pay for a commercial forecast specific to their actual location.

 

As far as I am concerned the forecasts for Watford, where I live appear to be reasonable accurate - not so many low temperatures are being forecasted these days because over the past 20 or so years there has been a general trend upwards in the winter and there seems to be nothing like the ice days we used to have, especially those with a -5C max which used to occur at more frequent intervals, though not necessarily every year.

[picog]

Certainly for this area, the BBC forecasted temps do tend to be too high in the winter, mostly at night, but quite often during the day too. Oftentimes, the difference at night can be 6 or even 7C, and what is OK for the towns turns into a proper frost for us.

I watched a BBC forecast today and temps from Mon through Thursday were double figures for here. The MetO 5 day forecast has no temp in double figures for the same time period, they are in the range 8-9C.

In the summer, the forecasted temps seem much more accurate. May be it is easier to get temps more accurate in the summer than the winter?

[Jax]

Here is a small town on the edge of a lot of rural/open countryside and it can vary in a small area, I have had a frost, yet a mile up the road did not, I work quite close to home, it is only a few miles as the crow flies, but there is a valley in there and a few high spots, it does make all the difference in a small area.

[The PIT]

They seem to get the night time temperatures very wrong over doing the heat island effect by quiet a bit. So if they say 9 degrees I wouldn't be surprised if we got 6C which is quite a difference. Day time they seem pretty good. Now whether it's because I'm on a hill and any heat island effect is lost by the breeze is another matter.

[MP-R]

I've noticed this as well but again probably because they cover quite a large area so take an average. I'm almost 4C lower in winter and 2-3C higher in summer than the value over my area on BBC forecasts. I'm also always amazed at how low they put London temperatures despite the fact it's warmer than all the areas around it.

[CongletonHeat]

The temps for here are always too low, many times over the xmas period it was supposed to be 6c and was always 7 or 8c.

[damianslaw]

The temperatures shown on the national forecasts are very misleading - they are representative of city centres mostly, and not representative of the countryside. Minimum temperatures are the same - skewed to take in the urban heat island effect. Occasionally the BBC show a map showing mins for the countryside especially when frost is forecast - however, as someone else has said they have to be quite conservative as they cannot represent micro climates.

 

The 5 day location forecasts are very poor for here, consistently overstating maxima by 2 or 3 degrees sometimes more! and understating minima. Take this evening at 7pm we should have been 2 degrees, yet we were close to -2 degrees..

[TonyH]

In fairness they often state that 'these are the temperatures in the cities' say +2c and it will be more like say -4c in the countryside. Of course then they are showing a temperature representative of a fairly wide area. Much local variation occurs within an area, my site is in a frost hollow and almost always several degrees below what is shown for a calm clear night. Another factor is that we may be judging by what our weather stations are showing and these can be inaccurate so they are best judged by recourse to the MO stations in that area.

[4wd]

As an example of how difficult it is, here is a wunderground list of online weather stations within about a ten mile radius of here.

This is a hilly area and some of the stations are in urban Teesside, some are quite high up and windswept, while some are in deeply rural sheltered valleys which can stay foggy and frosty all day while the high ground is +5C or more. Furthermore the chilly North Sea can have subtle or huge influence over just a couple of miles.
There are often great differences in local temperatures - and not in the way you might think - for example it's not unusual for stations near Teesside to be much colder then here on the moors if we are in a SW gale but they are sheltered and near freezing.

I'm sure similar variations are common elsewhere.

[Thundery wintry showers]

The BBC have often overstated maximum temperatures associated with northerly/north-westerly types for as long as I can remember.  I remember that in late January 2010 they predicted maxima of 5-7C from a northerly in Tyneside and in reality the maxima were between 2 and 4C.  I am not sure why this is, since it hasn't tended to happen when we've had cold easterly types.

 

With the minima I think that a change probably occurred in association with the graphics change back in 2005- in the old days they would often emphasise the lowest values.  The argument will most likely be that more people live in city centres than in prone frost hollows, which is very true, but then again, most people don't live in the centre of the urban heat islands.  But if you opt for something in between, you then have to decide what sort of area you want to represent if you want to be consistent- suburban or "peripheral city centre" perhaps?  Whatever they decide upon is likely to have some drawbacks.  

 

I've noticed that recently the BBC forecasts have been making more of a point of emphasising that values, especially for minimum temperature, are representative of town/city centres, and saying that values in rural/suburban areas will be up to a few degrees lower.  I think that is certainly a positive step.

 

The BBC 5-day forecasts, for whatever reasons, have always seemed to lag behind both the Met Office's 5-day forecasts and the BBC televised weather forecasts (which, incidentally, I think are back to being very good nowadays).

Edited January 4, 2015 by Thundery wintry showers

[Nick L]

As an example of how difficult it is, here is a wunderground list of online weather stations within about a ten mile radius of here.

This is a hilly area and some of the stations are in urban Teesside, some are quite high up and windswept, while some are in deeply rural sheltered valleys which can stay foggy and frosty all day while the high ground is +5C or more. Furthermore the chilly North Sea can have subtle or huge influence over just a couple of miles.

There are often great differences in local temperatures - and not in the way you might think - for example it's not unusual for stations near Teesside to be much colder then here on the moors if we are in a SW gale but they are sheltered and near freezing.

I'm sure similar variations are common elsewhere.

 

Indeed. 2 of my colleagues have weather stations, they live 7 miles apart yet the other night they had a 6c temperature difference.