Coldest 18th March since 1853

[xmetman]

Coldest 18th March since 1853

Don't forget that you can keep an eye on the latest daily CET values here

[John Hall]

I was hoping that yesterday's CET maximum would come in below zero, which would have made it easily the latest "ice day" in March since daily CET maxima become available in 1878. So 6th March 1942 retains the record. Of course, as yet yesterday's CET value is provisional, but it must be unlikely that it will be revised down far enough to make it negative. I'm a little surprised that it wasn't lower, especially in the light of the station values plotted on your map of the UK.

[xmetman]

John

You're right about the day max in the charts. The 06-18 max at Pershore was -0.3, and the max from Rothamsted -1.1, so the Stonyhurst max must have been well above freezing to have thrown the made the max positive, and in an easterly that looks very unlikely.

I think they work out the mean max and min by doing a calculation something like this:-  CET = ((2 x Rothamsted) + (1 x Pershore) + (1 x Stonyhurst)) /4

But it's the 09-09 extreme max and not just the 06-18 max that you get in a SYNOP.

Bruce.

[John Hall]

Ah yes, that would probably explain it. At 9 AM the sun has been up for almost three hours at this time of year, and by that time this morning the temperature might well have been slightly above freezing.

[Tezza]

Thanks for that Daily CET link.  There was a similar beautiful page somewhere that did the same thing but had to be pulled last year as the S/W became unsupported.  I've missed it ever since - until now.  

Cheers

[xmetman]

It's still very much work in progress - it's taking some time to get to grips with JavaScript once again.

[Tezza]

OK, thanks. Stupid question time:

How can the daily max (red dot) be lower than the average maximum for any specific day? Ditto minimum.

Be gentle...

[xmetman]

Tezza

1. The thicker dashed red and blue lines represent the 7 day centred moving average, and because they are centred they will always run 3 days behind the latest data.
   
2. The red and blue area graphs behind them represent the max and minimum daily extremes since the max/min series started in 1878.
   
3. The two series which lie within the extreme series (small black dots) are the daily maximum and minimum 1961-1990 long-term averages. 
4. The square red and blue scatter graph points are the actual daily maximum and minimum values.
5. If the red dashed line is blow the top dotted black line it was colder than average.

The recent cold spell is just starting to effect the 7 day moving averages, but because it's been short lived then it will only produce a small dip in the long term average.

If I made the moving average period 5 days instead of 7, the graph would make more of this cold spell but it would also make the graph a lot more spiky.

Bruce.

[Tezza]

Hiya Bruce,

Many thanks for the explanation.

Cheers

T