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Roger J Smith

April 2019 C.E.T. and EWP forecast contests

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12 hours ago, kold weather said:

I think globally 30 years is about the limit, but I'd love to see a 100yr mean used in the UK say 1900-2000. It's long enough that a couple of freak months either way won't impact the mean much and would really highlight the exceptional months when they come. 

Thats not a bad idea not for this comp but for general use.

One question to all, why do we have a 30 year average why not 50 years or so.
Is it just because the MO fixed that reference for their use.

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Sunny Sheffield at 6.7C -0.1C below normal. Rainfall unchanged.

A year mean any cold months wouldn't have much effect on the over average.

If the met office isn't going to use the latest 30 year mean then why should it publish them?

Judging by the comments made by the Beeb forecasters they're using the 81 - 10 averages if they're not they getting the average values of by a long way :)

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Posted (edited)

I don't know why 30 years was originally chosen but it is an international standard so was likely a concept of some early consensus of climatologists that became the general standard in the International organization and its member countries. I know it has been in use for a while because when I first became interested in weather we were using the 1931-60 normals. 

As to which 30 year interval is the benchmark, the two North American agencies use 1981-2010 and are quite fast to update to the latest 30-year normal at the start of the new decade. It's easy enough to have January normals ready to go on first of January then collect the December 2020 stats and publish 1991-2020 normals fairly early in the calendar year. 

Then again, as to why they don't update every year, after all just because years end in zero means very little to a climate analysis, I suppose it's a habit that won't easily change but there is no really valid reason not to have the latest available 30-year average and we do that here in our contest tables. At the moment, counting Jan, Feb and Mar 2019, these are the CET normals of the most recent 30 years available (none of Jan to Mar change the one decimal value from 1989-2018), followed by 1981-2010, 1971-2000, 1961-1990, and all 360 (or 361 for Jan-Mar) years, as well as 1901-2000 and Dalton (1801-1830) and Maunder (1671-1700) samplers ...

CHANGING 30-YEAR NORMAL VALUES

Month ___ Most recent __ 1981-2010 _ 1971-2000 _ 1961-1990 _ 1659-2018 _ 1901-2000 _ 1801-1830 _ 1671-1700

JAN _____ 4.7 __________ 4.4 _______ 4.2 _______ 3.8 _______ 3.3 _______ 3.9 _______ 2.5 _______ 2.6

FEB _____ 4.9 __________ 4.4 _______ 4.2 _______ 3.8 _______ 3.9 _______ 4.0 _______ 4.0 _______ 2.6

MAR _____6.8 __________ 6.6 _______ 6.3 _______ 5.7 _______ 5.3 _______ 5.8 _______ 5.5 _______ 4.4

APR _____8.8 __________ 8.5 _______ 8.1 _______ 7.9 _______ 7.9 _______ 8.1 _______ 7.9 _______ 7.1

MAY ____ 12.0 _________11.7 ______ 11.3 _______11.2 ______ 11.2 ______ 11.4 _______11.4 ______ 10.7

JUN ____ 14.6 _________ 14.5 ______14.1 _______14.2 ______ 14.3 ______ 14.2 ______ 14.2 ______ 13.9

JUL ____ 16.9 __________16.7 ______16.5 _______16.1 ______ 16.0 ______ 16.1 ______ 15.8 ______ 15.5

AUG ____16.5 _________ 16.4 ______ 16.2 _______15.8 ______ 15.6 ______ 15.8 ______ 15.4 ______ 14.9

SEP ____ 14.2 _________ 14.0 ______ 13.7 ______ 13.6 ______ 13.3 ______ 13.5 ______ 13.1 ______ 12.3

OCT ____ 11.0 _________ 10.7 ______ 10.4 ______ 10.6 _______ 9.7 ______ 10.2 _______ 9.8 _______ 9.0

NOV _____7.4 __________ 7.1 _______ 6.9 _______ 6.6 _______ 6.1 _______ 6.5 _______ 5.9 _______ 5.3

DEC _____4.9 __________ 4.6 _______ 5.1 _______ 4.7 _______ 4.1 _______ 4.6 _______ 3.6 _______ 3.3

YEAR ___10.2 _________ 10.0 _______ 9.7 _______ 9.5 _______ 9.2 _______ 9.5 _______ 9.1 _______ 8.5

______________________________________________________________________________

Here's an odd fact, the warmest 30-year interval for each month has occurred in the very recent past for all months except December (1971-2000 was the peak at 5.1) and June (14.72 from 1822 to 1851). There were other 30-year intervals that rounded to 14.7 -- 14.66 in 1821-1850, 14.68 in 1817-1846, and even earlier 14.70 for 1772 to 1801, preceded by 14.66 and 14.68, then also 14.65 for 1759 to 1788. There were clusters above 14.6 in the early 18th century. We have just returned to 14.64 for the first time since 1825-54 and will round to 14.7 again for 1990-2019 if June exceeds the dropped 1989 value of 14.6 (by 0.2, 14.7 will leave it just shy). To exceed the two-decimal maximum for June (14.72) would take a very warm 17.5 this year. 

Those "most recent" values are a fairly good indicator of what the 1991-2020 normals will be, especially given that the rest of 1989 and all of 1990 were relatively warm so losing them to rest of 2019 and all of 2020 won't likely bump these averages up by very much. That July value of 16.9 could drift down to 16.8 without much trouble. 

 

 

Edited by Roger J Smith

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Posted (edited)

Something that might surprise you is that from April to September, the 1961-1990 normals are basically similar to the all-time averages for 1659-2018 while the winter half of the year (October to March) shows an increase except for February which was actually a touch colder than the long-term average. Those trends have changed to slight warmings confined to June within the summer half year and considerable warmings in the winter half year. June seems to be the last of the herd to respond to the warming signal anyway. 

Edited by Roger J Smith

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Think I'm going to be way, WAY off the mark with my CET predication for this month.  Looks set to get even colder over the weekend before a (rather slow) trend back towards average.

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From the Hadley tracker it would appear we have reached about 25 mm on the EWP, adding small amounts to what they report for the 7th. Amounts indicated on the GFS model now to 25th are not that great, with just one slight event and one moderate one shown. I will post the potential scoring for 50 mm just so you can see how that scenario works for or against your prediction (without endorsing it as an actual outcome, just something to look at for now). If 50 or very close verified, nobody would have a perfect score because closest forecast (Daniel has 50 mm) has a late penalty attached. 

I would estimate that the CET is going to stay near 7 for quite some time if it creeps up a bit towards 8 it will fall back towards 7 at least once if not twice (if the GFS is anywhere near being right which we all know is a big IF). 

(provisional scoring if April 50 mm)

 

 

 

EWP20182019e.xlsx

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7.5c to the 8th

1.0c above the 61 to 90 average

Bang on the 81 to 10 average

_______________________________

Current high this month 8.1c to the 1st

Current low this month 5.9c to the 4th

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Sunny Old Sheffield on 6.9C bang on average, Rainfall Unchanged

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A marked downward fall expected in the days ahead, some very cold minima for time of year and cold maxima. A warm up next week though, so we might dip below 61-90 average briefly before a slight climb. Jury out still how the latter part of the month may pan out. 

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On 09/04/2019 at 19:17, Earthshine said:

Think I'm going to be way, WAY off the mark with my CET predication for this month.  Looks set to get even colder over the weekend before a (rather slow) trend back towards average.

 

20 hours ago, Roger J Smith said:

From the Hadley tracker it would appear we have reached about 25 mm on the EWP, adding small amounts to what they report for the 7th. Amounts indicated on the GFS model now to 25th are not that great, with just one slight event and one moderate one shown. I will post the potential scoring for 50 mm just so you can see how that scenario works for or against your prediction (without endorsing it as an actual outcome, just something to look at for now). If 50 or very close verified, nobody would have a perfect score because closest forecast (Daniel has 50 mm) has a late penalty attached. 

I would estimate that the CET is going to stay near 7 for quite some time if it creeps up a bit towards 8 it will fall back towards 7 at least once if not twice (if the GFS is anywhere near being right which we all know is a big IF). 

(provisional scoring if April 50 mm)

 

EWP20182019e.xlsx 56.38 kB · 2 downloads

Sounds daft but i don't think people who went high are out the equation, i would not even rule out my 9.5 yet, last week too far off to predict and 20c max and 7-9c minimums are not out the question in the last week of April if you got Southerlies, that would shift it up by 2 degrees easily.

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7.6c to the 10th

1.0c above the 61 to 90 average

Bang on the 81 to 10 average

_______________________________

Current high this month 8.1c to the 1st

Current low this month 5.9c to the 4th

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Sunny Sheffield at 6.8C -0.1C. Rainfall unchanged. Today was milder than forecast with temps above normal by day so there will be pause in the drop. If the next few days are milder than forecast we will remain close to the average value so we are looking probably at another possible very mild month again

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Another warmer than average month looking likely now.

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Expecting a marked downward adjustment in CET values this month, current running mean looks too high, isn't factoring into account the low minima..

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7.4c to the 11th

0.7c above the 61 to 90 average

0.2 below the 81 to 10 average

_______________________________

Current high this month 8.1c to the 1st

Current low this month 5.9c to the 4th

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Very slow drop in Sunny Sheffield down to 6.7C -0.3C below normal. Rainfall unchanged at 5mm 7.9% of the monthly average.

I can't see there being a massive downward adjustment in the finally figure. Even today being cold is only drop the figure down by a little amount. We did start from a low point so the mild spell just cancelled that out.

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EWP tracker was 25 mm after 10th, not likely to add much in the next ten days according to GFS 12z output, then could start to climb after 22nd. 

Looking at temperature trends on the 12z GFS, would say the current provisional CET would drop to about 7.0 by Monday 15th then rise gradually to a high point near 8 C by the Easter weekend. The trends beyond day ten look very cold with arctic air flooding south. Obviously not that reliable but it would, if any guide to reality, drop the CET values gradually back through the 7's. If we were at 8.0 on the 22nd, an average of 5 (about as low as could be imagined) for 23rd to 30th would leave the outcome at 7.2 C. I could also see there being a downward adjustment with the cold nights in recent days perhaps being under-valued in the provisional to date. 

However, with faint warming trends in a prolonged blocking pattern, you can always get into accelerated warming too, so I don't think too many forecasts are necessarily ruled out yet, all depends on that trend in the last ten days. 

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7.2c to the 12th

0.5c above the 61 to 90 average

0.4 below the 81 to 10 average

_______________________________

Current high this month 8.1c to the 1st

Current low this month 5.9c to the 4th

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I can well see the second half averaging 10C or more. I'm thinking a finish in the 8s looks good right now, better chance of above 9 than below 8 imo. 

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7 hours ago, Man With Beard said:

I can well see the second half averaging 10C or more. I'm thinking a finish in the 8s looks good right now, better chance of above 9 than below 8 imo. 

Agree with that, 8.5 to 9c is what I see atm.

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Sunny Sheffield at 6.3C -0.9C below normal. Rainfall unchanged.

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7.1c to the 13th

0.3c above the 61 to 90 average

0.5 below the 81 to 10 average

_______________________________

Current high this month 8.1c to the 1st

Current low this month 5.9c to the 4th

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Currently running at 7.9C for the April mean at my station.  Looks like next week may very well bump that a couple of degrees especially if the milder weather is sustained!

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6.0c here to the 13th, 0.9c below the 1981-2010 average.

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