In article
,
Teignmouth writes:
Not sure if I'm reading this correct, and it's from Wikipedia, but 3
Standard Deviations = 1 in 370 years, 4 Standard Deviations = 1 in
15,787 years, and 5 Standard Deviations = 1,744,277 years.
http://en.wikipedia.org/wiki/Normal_distribution

I've calculated the December mean from 1971 - 2009 as +5.0c, with a
Standard Deviation of 1.5c, so by my calculations the current CET that
is running at -2.0c is somewhere between 4 & 5 Standard Deviations.


But you aren't comparing like with like. There is going to be much
greater variation in the average for a spell of 7 days (1st to 7th
December) than there is for the whole month. If the average CET for the
whole month turned out to be -2.0C - or even anywhere near that - then
it really would be something.
--
John Hall
"I look upon it, that he who does not mind his belly,
will hardly mind anything else."
Dr Samuel Johnson (1709-84)

On Dec 7, 7:43*pm, "Lawrence Jenkins" wrote:
Some amazing charts tonight there's one synoptic set up showing as Steve
Murr said on TWO -a cross polar flow. Now that really does look grotesquely
specialhttp://www.meteociel.fr/modeles/ecmwf/run/ECH1-216.GIF?07-0

It's like the NH climate is taking drugs !!!!!! *Quite unerving to see such
set ups

If ever a blocking high was saying "thou shalt not pass" then today's
EC T+168 is just that - enormous axis from Greenland down to Spain
(with a low over the Azores - will be giving a low NAO signal),
different from yesterday's T+192. Clearly issues with understanding
the main high for next week!

Richard

On Dec 8, 6:28*pm, John Hall wrote:
In article
,

*Teignmouth writes:
Not sure if I'm reading this correct, and it's from Wikipedia, but 3
Standard Deviations = 1 in 370 years, 4 Standard Deviations = 1 in
15,787 years, and 5 Standard Deviations = 1,744,277 years.
http://en.wikipedia.org/wiki/Normal_distribution

I've calculated the December mean from 1971 - 2009 as +5.0c, with a
Standard Deviation of 1.5c, so by my calculations the current CET that
is running at -2.0c is somewhere between 4 & 5 Standard Deviations.

But you aren't comparing like with like. There is going to be much
greater variation in the average for a spell of 7 days (1st to 7th
December) than there is for the whole month. If the average CET for the
whole month turned out to be -2.0C - or even anywhere near that - then
it really would be something.
--
John Hall
* * * * * * * *"I look upon it, that he who does not mind his belly,
* * * * * * * * will hardly mind anything else."
* * * * * * * * * * * * * * * * * * * * * *Dr Samuel Johnson (1709-84)

John, I forgot to say in my analysis that I was stating that if it
continued and ended up at -2c for the whole month it would be between
4 & 5 Standard Deviations, but obviously it probably won't stay that
way.

Prodata, I use an Excel Spreadsheet Function *(STDEV) which estimates
the Standard Deviation based on a sample of the data set 1971-2009 so,
can't say whether they are normally distributed as I don't have a
degree in maths. There is also a SKEW Function, but I'm not sure how
to use that one with the STDEV Function.

If I use STDEVP the Standard Deviation for 1971-2009 is still 1.5c.

*Excel Functions:

STDEV Estimates standard deviation based on a sample
STDEVA Estimates standard deviation based on a sample, including
numbers, text, and logical values
STDEVP Calculates standard deviation based on the entire population
STDEVPA Calculates standard deviation based on the entire population,
including numbers, text, and logical values


The mean December CET for the whole data set from 1659 to 2009 is
+4.1c, with a Standard Deviation of 1.7c, so 3 Standard Deviations =
-1.1c, 4 Standard Deviations = -2.8c & 5 Standard Deviations = -4.5c.

I get the same result for 1659 to 2009 if I use the STDEVP Function.

Hope that helps.

oh so the record recent breaking weather is just normal is it?

you have no idea, clue or a brain cell.

just cant take the fact meto and will are miles ahead of you.

still waiting for your credentials.

go away you ogre "mildy".


On 07/12/2010 8:07 PM, Dawlish wrote:

Will, calm down. This ramping is getting silly. It's only 3 weeks
since you forecast an average winter and were seeing no signs that it
would be as cold as the last one. Now the winter is going to be
"historic". Which is correct and what has changed in 3 weeks? The
charts show cold out to 10 days. No-one knows what the weather will be
like much after that. The winter may indeed be "historic", but as
absolutely no-one was forecasting that for the UK 3 weeks ago, why
should we believe anyone who is now forecasting it 3 weeks later? What
this proves is that either your original forecast is a guess (unless
it turns milder by Christmas and stays reasonabley mild with a few
colder spells, which it could do, of course) or this spot of ramping
is a hopecast.

Happens every winter. It's just that this winter, it is presently
cold, so we get this silly desperate hoping that we'll see a winter of
epic proportions. We may, but at this stage, just like 3 weeks ago, no-
one knows.

Dawlish wrote:


errrrrrrrr. No. Not when it is daft. Like I said; calm down. People
have just as much right to criticise the ramping as the rampers have
to ramp. (I do hate that word, but that's what coldies do when it is
cold, or further cold is possible!). No-one can forecast at 2 weeks
with any record of reasonable accuracy, so best not to believe the
ones that do, even when they are "forecasting" exactly what you want
to see forecast.

And people have a right to criticise those who criticise the rampers.
etc, etc
--
Col

Bolton, Lancashire
160m asl

On Dec 8, 7:30*pm, "Col" wrote:
Dawlish wrote:

errrrrrrrr. No. Not when it is daft. Like I said; calm down. People
have just as much right to criticise the ramping as the rampers have
to ramp. (I do hate that word, but that's what coldies do when it is
cold, or further cold is possible!). No-one can forecast at 2 weeks
with any record of reasonable accuracy, so best not to believe the
ones that do, even when they are "forecasting" exactly what you want
to see forecast.

And people have a right to criticise those who criticise the rampers.
etc, etc
--
Col

Bolton, Lancashire
160m asl

Heh. Absolutely!

better to have something to ramp about billy no mates. heh?

still waiting for you credentials and winter LRF

On 08/12/2010 7:33 PM, Dawlish wrote:

Heh. Absolutely!

In article
,
Teignmouth writes:
Prodata, I use an Excel Spreadsheet Function *(STDEV) which estimates
the Standard Deviation based on a sample of the data set 1971-2009 so,
can't say whether they are normally distributed as I don't have a
degree in maths. There is also a SKEW Function, but I'm not sure how
to use that one with the STDEV Function.

ISTR that for the winter months the distribution is skewed, with the
coldest months in the whole CET series being below the mean by more than
the warmest months are above it. (That means that there are rather more
months above the mean than below it, ie the median is rather greater
than the mean.)
--
John Hall
"I look upon it, that he who does not mind his belly,
will hardly mind anything else."
Dr Samuel Johnson (1709-84)

John,

If I use the SKEW function I get the following values:

Period Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1659-2009 (0.6) (0.5) (0.1) (0.1) 0.1 0.2 0.4 0.3 0.0 (0.1) 0.0
(0.2)
1971-2009 (0.8) (0.8) (0.2) 0.2 (0.1) (0.2) 0.8 0.4 (0.1) 0.0
(0.1) (0.8)

Now what do I do with the value and the Standard Deviation?

If I have a December mean for the period 1659-2009 of +4.1c, and the
STDEV is 1.7c, and the SKEW is -0.2c, do I get a revised STDEV of 1.5c
or 1.9c? Then do I use +4.1c and the revised STDEV x1 x2 x3 etc to
get the revised Standard Deviation thresholds?

Your help is much appreciated.

Thanks

In article
,
Teignmouth writes:
John,

If I use the SKEW function I get the following values:

Period Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
1659-2009 (0.6) (0.5) (0.1) (0.1) 0.1 0.2 0.4 0.3 0.0 (0.1) 0.0
(0.2)
1971-2009 (0.8) (0.8) (0.2) 0.2 (0.1) (0.2) 0.8 0.4 (0.1) 0.0
(0.1) (0.8)

Now what do I do with the value and the Standard Deviation?

If I have a December mean for the period 1659-2009 of +4.1c, and the
STDEV is 1.7c, and the SKEW is -0.2c, do I get a revised STDEV of 1.5c
or 1.9c? Then do I use +4.1c and the revised STDEV x1 x2 x3 etc to
get the revised Standard Deviation thresholds?

Your help is much appreciated.

Thanks


Sorry, but my statistics knowledge is not good enough to help. I know
about "vanilla" Normal distributions, but not about skewed ones. I'm
sure that we have at least one or two stats experts here though.
--
John Hall
"I look upon it, that he who does not mind his belly,
will hardly mind anything else."
Dr Samuel Johnson (1709-84)