April CET

[Bottesford]

I think its easier to acheive mild nights in autumn compared to spring I would have thought due to all that latent heat in the seas. Whether that makes any difference to where records are falling I'm not sure.

[parmenides3]

I know you weren't, I was just postulating the required output.

P3 - have to disagree, 7.2 would look VERY out of place in April given the recent trend for warming (0.9 below the 71-00 average) as would the current 9.5 in May (a full 1.8 below the 71-00 average)

Manley (link to Phillip's site here) has the CET to the 13th at 9.5

To get a record April, 11.5 required from here on in - certainly the next 3 days will be a good start but likely falling back after that for a time.

Feb.'s figure was nearer to the march average than the Feb. average; March's figure was mid-way between the March and April averages, and April to date (and possibly through to the end of the month) is closer to May's average than April's. It was just a bit of speculation, really, but if you were to shift the month-end date back 15 days, it would be interesting to see how close the adjusted figures would be to the relevant month's average.

This isn't really that serious a point, just a thought...

:)P

[Snowly does it]

Feb.'s figure was nearer to the march average than the Feb. average; March's figure was mid-way between the March and April averages, and April to date (and possibly through to the end of the month) is closer to May's average than April's. It was just a bit of speculation, really, but if you were to shift the month-end date back 15 days, it would be interesting to see how close the adjusted figures would be to the relevant month's average.

This isn't really that serious a point, just a thought...

:)P

No fair enough I just think the Spring Temps expressed as the CET average (and depending on what happens this weekend and after!) are really not very eye-catching at all - its the preceeding 8 months that have coloured them - they are a little above average (April becoming very much above average), but on the back of a record Autumn and near-record winter they look rather more impressive than they are imo. 7.2 in March - there have been only 3 Marches cooler since 1997 (which says more about the trend than the last year imo)

In respect of the Feb average, if we accept the trend for warming which we all do, it was much closer to its rolling 10 year mean then the rolling 10 year mean for March, in fact Feb and March were just 0.3 and 0.1 above their respective 10 year means and April at 9.0 would continue that average nicely - the 'lurch' flattening? (not an entirely serious point either as statistically I will get mooshed by SF)

[Thundery wintry showers]

Re. March's comparison being more relevant to the last 10 years, this is very true.

No decade until the 1990s had an average March CET of 6.0 or above; most decades in the 20th century were between 5.5-5.9C CET and earlier centuries were often nearer 5C CET.

The 1990s and 2000s saw the figure leap upwards, with a mean pushing above 7C. This March was unremarkable compared to the 10-year mean, or even the 20-year mean, but in the context of any other reference period it was a mild month.

[Stratos Ferric]

Re. March's comparison being more relevant to the last 10 years, this is very true.

No decade until the 1990s had an average March CET of 6.0 or above; most decades in the 20th century were between 5.5-5.9C CET and earlier centuries were often nearer 5C CET.

The 1990s and 2000s saw the figure leap upwards, with a mean pushing above 7C. This March was unremarkable compared to the 10-year mean, or even the 20-year mean, but in the context of any other reference period it was a mild month.

Precisely, and reference SM's post immediately prior, this is the point. We are requiring ever shorter frames of reference in order to make even weak arguments for normality. Compared to the standard reference period - which is chosen for statistical robustness - pretty much every month since last August has been noteworthy: the sequence as a whole is absolutely exceptional.

P3s' post is interesting, even if it only points out in other terms the shortening of the winter period from both ends of the calendar.

[Snowly does it]

Precisely, and reference SM's post immediately prior, this is the point. We are requiring ever shorter frames of reference in order to make even weak arguments for normality. Compared to the standard reference period - which is chosen for statistical robustness - pretty much every month since last August has been noteworthy: the sequence as a whole is absolutely exceptional.

P3s' post is interesting, even if it only points out in other terms the shortening of the winter period from both ends of the calendar.

Yes, but the shorter reference is more appropriate here. We know the world is warming and thus the 71-00 average is all but useless, how can a month even begin to be referenced to a climate that no longer exists? Yes the months are all exceptional against the 71-00 mean but if a month over a degree above 'normal' or even say a degree and a half is exceptional and the UK is around a degree warmer than the reference period then its fairly likely we will see such runs - its the record Autumn (Sept/Oct only) and July that stand out, December and Jan being noteworthy but El Nino influenced. The rest are nothing to write home about. It depends what needs to be shown here - warming? Yep, undoubtedly, a degree of warming? Yes, undoubtedly. A climate lurch? Looks less likely from the data November onwards given El Nino.

April does have a very good chance of being well above normal standing at 9.8 with two more days of big rises to come (taking it to maybe 10.5), we will do well to break 9 downwards from here.

Edited April 15, 2007 by snowmaiden

[Weather-history]

The driest month of this decade so far for England and Wales is August 2003 with 21.3mm

Driest April on record for England and Wales was April 1938 with 7.1mm

Rainfall trackometer for April 1938 (mm)

1. 0.2

2. 3.1

3. 3.2

4. 3.6

5. 3.7

6. 3.7

7. 3.7

8. 3.7

9. 3.7

10. 3.7

11. 3.7

12. 3.7

13. 3.7

14. 3.7

15. 3.7

16. 3.7

17. 3.7

18. 3.9

19. 3.9

20. 3.9

21. 4.0

22. 4.4

23. 4.8

24. 5.1

25. 5.3

26. 5.3

27. 5.4

28. 5.5

29. 6.2

30. 7.1

The last sub 10mm month was August 1995 with 9.1mm

Sunniest April in the Areal series is 1984 with 217.5 hrs

The sunniest spring in the Areal series is 1948 with 598.7hrs

[Optimus Prime]

Well we're 0.8mm by the 14th so it's much drier then 1938 already upto this point. The odds of a CET above 10.0c now looks very slight. Some low minima next week could push the CET down close to 9.0c by months end.

[Stratos Ferric]

Yes, but the shorter reference is more appropriate here. We know the world is warming and thus the 71-00 average is all but useless, how can a month even begin to be referenced to a climate that no longer exists? Yes the months are all exceptional against the 71-00 mean but if a month over a degree above 'normal' or even say a degree and a half is exceptional and the UK is around a degree warmer than the reference period then its fairly likely we will see such runs - its the record Autumn (Sept/Oct only) and July that stand out, December and Jan being noteworthy but El Nino influenced. The rest are nothing to write home about. It depends what needs to be shown here - warming? Yep, undoubtedly, a degree of warming? Yes, undoubtedly. A climate lurch? Looks less likely from the data November onwards given El Nino.

April does have a very good chance of being well above normal standing at 9.8 with two more days of big rises to come (taking it to maybe 10.5), we will do well to break 9 downwards from here.

This is where, and why, statistics can get a bad name. THe fact that we're warming doesn't of itself render the 71-00 baseline useless; it depends what you're trying to use thenumbers to show. To illustrate warming (or anything) WITH ROBUSTNESS you simply HAVE to use a long reference period (usually 30 data points or more, though once you get upwards of 60 or so the statistical gain is very slight, and beyond 100 it's really hardly worth the bother) to get the degrees of freedom in the data set, otherwise potential volatility in the data cannot be ruled out as the driver of a signalled difference.

I agree, in assessing how unusual months are in the current sharp upwards movement, one has to use a shorter period, but the risk to the untrained eye is that the "dampening" of effect so introduced can be taken to indicate a slow down. It's rather like the difference between acceleration and speed. The thirty year comparison is far better for illustrating the acceleration, though as I invariably point out on these threads, for the purposes of making a prediction the 30 year reference is defunct IF you don't build in the current tendency - which is more or less invariable - for monts to land well above this line. All the ten year reference does is account for this adjustment.

Sub 9.0 for the month is now all but dead. We're likely to be 10.3 or 10.4 after tomorrow, and even through to Thursday I don't see any more than a very slight downward correction. At something like 25 degree days up by the 18th, it would require an average of 7C to the month's end to get back down below 9. The baseline now looks low 9s, with the ceiling probably around 10.

Edited April 15, 2007 by Stratos Ferric

[Snowly does it]

Sub 9.0 for the month is now all but dead. We're likely to be 10.3 or 10.4 after tomorrow, and even through to Thursday I don't see any more than a very slight downward correction. At something like 25 degree days up by the 18th, it would require an average of 7C to the month's end to get back down below 9. The baseline now looks low 9s, with the ceiling probably around 10.

Yes, ok I agree with you there and it is indeed down to what we want them to demonstrate.

As an example, if April came in at say 9.0 this would be 0.9 above the long term and 0.2 above the 10 year mean - making the Feb-April period 0.3, 0.1 and 0.2 above the 10 year mean. I think that shows we are progressing out of an El Nino winter at around the levels one would expect against the estabished warming with perhaps a further fraction of a degree being seen - short term yes and proof positive no but certainly the last few months are beginning to move away (it seems at the moment) from 'record' to 'new status quo' levels, thats how it seems to me anyway.

[Stratos Ferric]

Yes, ok I agree with you there and it is indeed down to what we want them to demonstrate.

As an example, if April came in at say 9.0 this would be 0.9 above the long term and 0.2 above the 10 year mean - making the Feb-April period 0.3, 0.1 and 0.2 above the 10 year mean. I think that shows we are progressing out of an El Nino winter at around the levels one would expect against the estabished warming with perhaps a further fraction of a degree being seen - short term yes and proof positive no but certainly the last few months are beginning to move away (it seems at the moment) from 'record' to 'new status quo' levels, thats how it seems to me anyway.

It certainly seems to be the case that the lurch we saw in autumn through to January seems to have slowed, but given that we have still got +ve anomalies, even over the ten year comparison, we are still warming above trend. We are, if you like, accelerating less quickly, but we have not stabilised.

[parmenides3]

Am I right in thinking that such issues are why the CRU/NCDC/Hadley datasets for climate are expressed in terms of anomalies, rather than absolute temperatures? there are probably good reasons for thinking in terms of ten-year 'sets', inasmuch as many climatic shifts are identifiable on the decadal time scale, but the thirty-year standard is used for good reasons. Perhaps it is better to think in terms of relative anomalies rather than relative temperatures, if we want to forecast a month ahead? Still just the odd thought.

:)P

[Kentish Man]

Can't see much downward correction if GFS is to be believed. A few cooler nights from next Thursday to Sunday but daytime temps only falling to average followed by a warm up again after next weekend to the end of the month. 10C or above still very much on.

[summer blizzard]

The driest month of this decade so far for England and Wales is August 2003 with 21.3mm

Driest April on record for England and Wales was April 1938 with 7.1mm

Rainfall trackometer for April 1938 (mm)

1. 0.2

2. 3.1

3. 3.2

4. 3.6

5. 3.7

6. 3.7

7. 3.7

8. 3.7

9. 3.7

10. 3.7

11. 3.7

12. 3.7

13. 3.7

14. 3.7

15. 3.7

16. 3.7

17. 3.7

18. 3.9

19. 3.9

20. 3.9

21. 4.0

22. 4.4

23. 4.8

24. 5.1

25. 5.3

26. 5.3

27. 5.4

28. 5.5

29. 6.2

30. 7.1

The last sub 10mm month was August 1995 with 9.1mm

Sunniest April in the Areal series is 1984 with 217.5 hrs

The sunniest spring in the Areal series is 1948 with 598.7hrs

Having looked at the latest model outputs and data from www.climate-uk.com, i think that there is a good chance of us having the driest month this decade, however i do not believe that we will have a drier month than August 1995, and definitely not the driest April on record.

As for sunshine, while it is a different series, going by Phillip Edens site, i believe that we are on course for the sunniest April on record.

The CET is currently 9.8C according to Phillip Eden and will go above 10C today, assuming a correction down to about 9.5C by the 23rd, i believe that there is a good chance of a near record month given that there is good agreement on the ensembles, for high pressure to provide a dry, sunny, warm but crucially more westerly flow, which i think may produce higher minima, i dont anticipate a record month but i think that there is a good chance of 10C+.

[Stratos Ferric]

Am I right in thinking that such issues are why the CRU/NCDC/Hadley datasets for climate are expressed in terms of anomalies, rather than absolute temperatures? there are probably good reasons for thinking in terms of ten-year 'sets', inasmuch as many climatic shifts are identifiable on the decadal time scale, but the thirty-year standard is used for good reasons. Perhaps it is better to think in terms of relative anomalies rather than relative temperatures, if we want to forecast a month ahead? Still just the odd thought.

:)P

I wasn't aware that Hadley is expressed in terms of anomalies. The downloadable data is absolute: anomalies are just a statement of net difference. Ordinarily a ten year cycle is probably going to be influenced more by short-term variability than it is by general apparent climatic stasis. Hence, if you go carve any thirty year period into its three constituent decdes, each decade will have a characteristic of its own. The argument over the last thirty years would be that each decade is warmer than the one before, suggesting a warming trend ongoing. Even so, in any trend, there are still short-term variations up and down, and if the period of these is, say, ten years, then short-term comparison becomes mudied.

The long and short of it is that to use time series to understand patterns you need to use three or four different series: this is precisely what chartists in the city do to predict stock movements: in particular, you look for a sequential alignment of the series arranged by time order in order to predict a strong and sustained movement: i.e. the weekly is above the monthly is above the quarterly is above the 365 day cycle (or below, in a bear market).

[Snowly does it]

It certainly seems to be the case that the lurch we saw in autumn through to January seems to have slowed, but given that we have still got +ve anomalies, even over the ten year comparison, we are still warming above trend. We are, if you like, accelerating less quickly, but we have not stabilised.

Although if we came in as stated as say 9 we could say we had stabilised at 0.2 above the running 10 year mean - to test the theory 'if' (and I know its a fairly big if in some ways) we come in at 9.0-9.2ish for April then I would back a yearly outcome of..... (Jan, Feb. March and assumed 9.1 April plus remainder on 10 year mean plus 0.2) - 10.86 and squeaking home with a new record.

So in terms of the 11plus etc we have discussed before we need to be warming well beyond the 10 year mean (with 0.2 correction as the plateau post-lurch). Food for thought if that record goes.

[kold weather]

By the way, while off-topic, does the April 06-April 07 get a 11C CET IF it does come out at say 9.5C (Which i think is about the most likely temp for April, i agree with SF in his ideas and 9.5C seems a nice little figure!)

Beyond then and we do see quite a cool-down, mins do look quite cold for the time of year and also for once the maxes also look slightly below average, which has been quite rar eover the last 45 days or so.

Saying al lthat after a breif correction in temps given the shape of the jet and where its heading I can only see a wind direction from a mainly south-westerly/southerly type of direction much like its been over the last 30 days.

[Stratos Ferric]

By the way, while off-topic, does the April 06-April 07 get a 11C CET IF it does come out at say 9.5C (Which i think is about the most likely temp for April, i agree with SF in his ideas and 9.5C seems a nice little figure!)

Beyond then and we do see quite a cool-down, mins do look quite cold for the time of year and also for once the maxes also look slightly below average, which has been quite rar eover the last 45 days or so.

Saying al lthat after a breif correction in temps given the shape of the jet and where its heading I can only see a wind direction from a mainly south-westerly/southerly type of direction much like its been over the last 30 days.

By my reckoning, at the end of April last year the rolling 12 month was 10.03. Assuming 9.5C this month we will be at another all time high of 11.52, though I haven't rechecked all the latest revisions to Hadley so I'm likely to be out by around 0.1C or so. May was about bang on 10 year trend last year, and June was only +1, so some further increase to the mid year point is likely. There are fairly short odds on a +11.00C year now, particularly if recent warmth continues into late spring.

[PersianPaladin]

I'm sticking by my original 9C prediction.

[Stratos Ferric]

I'm sticking by my original 9C prediction.

You're either bold or foolish my man!

[Stratos Ferric]

Indeed and it makes March 2006 especially look like a real outlier. It just seems these days that the odds are completely stacked against anything average, never mind cool. It really is hard to see where any cold weather is going to come from that allows a well below average month. The current trend seems to be for homogeneous mild weather, with any cold spells shortlived, only allowing a CET that isnt record-breaking, but still well above average.

I seem to recall that when I made that very point during the autumn BFTP, or was it AFF, took great exception. However, since we haven't seen its relative like for eleven years I think it's game, set, and point well made.

[Stratos Ferric]

Looking at the latest chart, and ahead of my mid month projection, we look likely to be nudging 11 by the end of the week (expect probably 0.8C uplift from yesterday + today), and a slight movement up on Tuesday + Wednesday. Thursday / Friday are not going to make much of a dent, and thereafter the month looks like it's warm side of normal and northwards of that. Not only is 9 / 9.5C looking like cert, but +10 is starting to seem quite plausible.

[PersianPaladin]

You're either bold or foolish my man!

Nope....it's called sticking by your guns. All this chopping and changing (even after the month begins) makes a guess look less educated and more on the whim.

Edited April 16, 2007 by PersianPaladin

[Joneseye]

The current N-W UK tracker figure for April 2007 is: 10.43°C

(difference from average April CET is 2.33°C)

CET: (Apr 1-15): 10.1°C (+2.4 degC) © Philip Eden

[Roger J Smith]

I would prefer 10.2 now.