C. Finch's 37- rule

[Terminal Moraine]

It might be worth resurrecting this 1960s/70s forecasting tool, firstly to see if this year qualifies and secondly to decide whether or not it applies 40 years on.

Colin Finch developed a rule which stated; if, over southern England, there was a period of at least 5 consecutive days between Dec' 11th and Dec 24th when the max' remained below 3.1c for 3 days and not higher than 4.7c on the other two,

then there was a much greater likelihood that severe cold spells would return during January and February.

Qualifying years in the 60s and 70s were 1962, 1963, 1968, 1969 and 1978, all of these were followed by cold spells during the remainder of the winter and, apart from 1964, there was a good deal of snow.

Is there anyone in the area between Surrey and Hants, north to about Berkshire who could confirm or otherwise whether or not the rule has been met this year?

Finch regarded this indicator as the strongest pointer to cold weather during the rest of the winter, overriding even SSTs, although if SSTs were below average all the better. If I remember correctly he backtracked it to the early years of the 20th century and found very few ( if any ) failures. The last year I can think of which may have met the criteria was Dec' 1995, perhaps someone can enlighten me if there have been any qualifying years since.

T.M

[Tom Quintavalle]

Hi TM,

I'm glad you've posted on this subject again. This is what I posted on the 8th Dec.

"I remember having a discussion with Terminal Moraine a couple of years ago regarding a theory of Colin Finch and A.N.Other. The theory suggests that if max.temps fail to reach 40f in old money on 4 consecutive days in the first 3 weeks of December, then the likelihood of further spells of cold weather during the rest of winter are more likely than if these criteria are not met. I cant quite remember what part of the country this applied to but as I heard this when Colin Finch was appearing on a London radio station back in the 70s, I think it probably suggests S.E.England. Now to me that kind of temp regime would suggest high pressure to the north/east or indeed a cold high sitting over the S/East. The forecast charts seem to be suggesting this kind of set-up with that kind of temp. regime. I dont think Decembers in recent years have produced these kind of synoptics. As we know only to well our winters have changed a fair bit since the 60s and 70s but if these forecasts come to fruition it will be interesting to test this theory out. If you read this TM please correct me if I've got my facts wrong!"

I couldnt quite remember the exact qualifying max. temps and period but I knew it was something along the lines that you mention. Off the top of my head I would say that we havnt quite met the qualifying criteria but it was a close run thing. I stand to be corrected of course!

Regards,

Tom.

[The PIT]

Well the test is going to come isn't it. Pretty sure this has happened over to Mr data

[BLAST FROM THE PAST]

There is no doubt this has happened...and IMO there is a very cold spell to occur from the back end of week one.

BFTP

[Stu_London]

There is no doubt this has happened...and IMO there is a very cold spell to occur from the back end of week one.

BFTP

Pretty sure 2007 will have qualified - less sure about 1995

[Weatherfanman]

I'm not so sure that the criteria will have been met. I admit I'm not in the zone, too far north, but the stubborn presence of floating cloud has at times kept the overnight temps up too much to overly suppress the following maxes........see attached for N Oxfordshire.

dec__07.xls

WFM

[Terminal Moraine]

Very interesting TM and quite compelling analogue years. I won't mention the M word but who would like to bet that this year bucks the figures ?

I wouldn't be entirely surprised, Ian. I seem to remember reading that Colin Finch also backtracked his rule into the 19th century but found it was wasn't as reliable then, more to do with the fact that non-qualifying Decembers were also followed by cold/severe spells during the following winter rather than qualifying Decembers being followed by mild winters if I remember correctly.

It's equally possible, the way things have been since around 1989, that 'rules' which have previously seemed almost infallible will be broken by the synoptics of the current period of warming, notwithstanding the cooling blip of the last few months.

T.M

[Stu_London]

I'm not so sure that the criteria will have been met. I admit I'm not in the zone, too far north, but the stubborn presence of floating cloud has at times kept the overnight temps up too much to overly suppress the following maxes........see attached for N Oxfordshire.

dec__07.xls

WFM

Very close near miss so likely somewhere might have hit the criteria - West of London has stayed pretty cold

[Rustynailer]

As temperature average is slightly higher than the 60s and 70s, perhaps the 37 rule may be the 40 rule or something like

[johnholmes]

I'm not so sure that the criteria will have been met. I admit I'm not in the zone, too far north, but the stubborn presence of floating cloud has at times kept the overnight temps up too much to overly suppress the following maxes........see attached for N Oxfordshire.

dec__07.xls

WFM

not that different from what I've had here; mean is now at 4.8C from 8.0C after the first 10 days.

[Terminal Moraine]

As temperature average is slightly higher than the 60s and 70s, perhaps the 37 rule may be the 40 rule or something like

I think that would be moving the goalposts to suit our aspirations, RN. According to Finch's original work the whole point of the temperature limitations imposed by the 'rule' was that it was the minimum requirement for a good chance of cold spells later in the winter. If the general climate has warmed so much that these criteria are no longer met, it's probably a good indicator that there are unlikely to be any serious cold spells during the oncoming winter ( assuming the 'rule' works in the first place )

T.M

[Polar Continental]

Yes sounds very interesting TM, especially as his rule had such a low failure rate.

Pity the rule didn’t extend to here in Staffs and south Derbyshire I am sure the criteria would have been met this December; with the mean max here in Burton over 7 days being 2.7c. Quite out of the ordinary really, even after 11 days the mean max is still at 2.7c.

Paul

[johnholmes]

yes, its a pretty cold spell by most standards for many people I think.

the mean temp here for the last 11 days is 1.5C.

it must be a long time since 11 days in any month gave that value.

[Anti-Mild]

I've just had a quick search in the CET data and the only years since 1988 that met the criteria were 1990 (see February 1991) and 1992 (possibly an exception to the rule although there was a huge blizzard in Scotland and N.England in early January).

1995 came close to meeting the criteria but not quite.

[ukmoose]

It might be worth resurrecting this 1960s/70s forecasting tool, firstly to see if this year qualifies and secondly to decide whether or not it applies 40 years on.

Colin Finch developed a rule which stated; if, over southern England, there was a period of at least 5 consecutive days between Dec' 11th and Dec 24th when the max' remained below 3.1c for 3 days and not higher than 4.7c on the other two,

then there was a much greater likelihood that severe cold spells would return during January and February.

Qualifying years in the 60s and 70s were 1962, 1963, 1968, 1969 and 1978, all of these were followed by cold spells during the remainder of the winter and, apart from 1964, there was a good deal of snow.

Is there anyone in the area between Surrey and Hants, north to about Berkshire who could confirm or otherwise whether or not the rule has been met this year?

Finch regarded this indicator as the strongest pointer to cold weather during the rest of the winter, overriding even SSTs, although if SSTs were below average all the better. If I remember correctly he backtracked it to the early years of the 20th century and found very few ( if any ) failures. The last year I can think of which may have met the criteria was Dec' 1995, perhaps someone can enlighten me if there have been any qualifying years since.

T.M

Well this is very interesting, TM. I haven't heard of Mr Finch, or his rule, but I had my own notion that a cold spell in December was almost a prerequisite for cold later in the winter. I mentioned this in another thread but I didn't have any evidence to support it. I based it on memory and gut feeling mostly - hardly scientific, I know. Stratos was unsure about my assertion but was thinking of looking for some figures to confirm or rebut it. It seems that you have unearthed the very factor I was talking about. I'm slightly further north than the zone you mentioned, but the temperatures fit the bill here.

It will be interesting to see what happens further down the line. Interesting stuff to me - thanks for posting it.

Moose