October 2023 C.E.T. and EWP contests

[Summer Sun]

14.6c to the 14th

4.1c above the 61 to 90 average
3.0c above the 81 to 10 average

[Metwatch]

EWP up to 51mm now following the deluge on Thurs/Fri night. Seems like models have trended much wetter from Wednesday, as the Scandi high looks to ebb away by next weekend. I think another 100mm+ October EWP seems likely now. Would be the 5th time running since 2019.

[richie3846]

8 minutes ago, Metwatch said:

EWP up to 51mm now following the deluge on Thurs/Fri night. Seems like models have trended much wetter from Wednesday, as the Scandi high looks to ebb away by next weekend. I think another 100mm+ October EWP seems likely now. Would be the 5th time running since 2019.

I err on the side of caution when trying to attribute short term trends to a particular reason. However, it does appear that Octobers of recent years, seem to be the dumping ground of the warmer conditions in the summer, in the Northern hemisphere, in the form of rain. I think it was October 2021 that saw the extreme rainfall event that has been quickly forgotten - because of lack of impacts. We dodged a bullet, simply because of a dry September, and the steady nature of the rain.

 

[Derecho]

I expect a big drop due to the cold weather of today with maxima struggling to get far into double figures following cold minima.

There may be some discrepancy over timings but judging by the EC 00z control these are the temperatures up to the 29th:

15th: 14.0C (6.1C - EC may be a bit on the cold side here)
16th: 13.6C (7.1C)
17th: 13.4C (10.0C)
18th: 13.3C (12.4C)
19th: 13.4C (14.7C)
20th: 13.4C (13.8C)
21st: 13.4C (12.0C)
22nd: 13.2C (10.3C)
23rd: 13.1C (10.3C)
24th: 13.0C (9.6C)
25th: 12.8C (10.1C)
26th: 12.8C (10.9C)
27th: 12.6C (9.1C)
28th: 12.5C (9.3C)
29th: 12.4C (8.7C)

So the EC Control sees an unremarkable second half of October if it came into fruition. A large amount of uncertainty however, the warmest run would have a CET of 13.3C by the 29th so it would be on track to be a record breaker. The coldest member has the CET at 11.6C by the same date.

The EC control as it stands is slightly cooler then the ensemble average. I'd guess mid to late 12s would be a sensible estimate to end the month at this early point.

[summer blizzard]

12.4C is required to avoid the top 11. 

[Weather-history]

56 minutes ago, richie3846 said:

I err on the side of caution when trying to attribute short term trends to a particular reason. However, it does appear that Octobers of recent years, seem to be the dumping ground of the warmer conditions in the summer, in the Northern hemisphere, in the form of rain. I think it was October 2021 that saw the extreme rainfall event that has been quickly forgotten - because of lack of impacts. We dodged a bullet, simply because of a dry September, and the steady nature of the rain.

 

100mm+ Octobers are nothing unusual. It is on average, one of the wettest months of the year.

[WYorksWeather]

57 minutes ago, Weather-history said:

100mm+ Octobers are nothing unusual. It is on average, one of the wettest months of the year.

Yep, in fact the long term average is just above 100mm.

[cheese]

1 hour ago, Weather-history said:

100mm+ Octobers are nothing unusual. It is on average, one of the wettest months of the year.

2nd wettest month of the year here, after August.

However October still only gets 56.7mm of rain on average here. In most of England there is very little variation in rainfall throughout the year, so ‘wettest month’ is very much relative…

Edited October 15, 2023 by cheese

[richie3846]

28 minutes ago, WYorksWeather said:

Yep, in fact the long term average is just above 100mm.

I may be guilty of some localism here. The last 4 Octobers have been wetter than average, with 2 of those very wet indeed. This followed 4 dry Octobers in a row. So locally we've literally flipped from dry to wet, with rainfall roughly 3.5 times the amount during 2019-22, compared with the dry Octobers 2015-18. 

[Roger J Smith]

In the invitation post I mentioned this:

The wettest 30-year average for October was 106.9 mm for 1865-1894, almost matched recently by 106.1 mm for 1986 - 2015 and 1993-2022. The driest 30-year average for October was 77.1 mm for 1946-75. 

Could add that as 1993 total was 94.4 mm, any outcome above 118 mm would make 1994-2023 wetter than 106.9 mm; every 3 mm added to total for 30 years adds 0.1 to average, so to get an increase of 0.8 requires 24 mm more rain in 2023 compared to 1993 as it drops out of total to be averaged.

A total of 137 mm was applied to scoring estimates in contest supporting excel file, and if we get to any outcome 120+ scoring will be similar, snowray (99 mm) manages to hold on to lead in contest, but Reef (131 mm) and Bobd29 close in with higher forecasts and Summer Shower (134 mm) and better scores for October, while current second place Leo97t (80 mm) drops back (if this happens). Leo97t could catch snowray if outcome avoids predicted amounts and stays below 80 mm. Bobd29 (112.5 mm) would be third in that scenario, and between second and fourth at various outcomes between 85 and 125 mm.

If I don't see trends wobbling in next few days, will post preliminary scoring estimates based on the latest outcome from guidance. In any case, the final stage of the contest (Nov 2023) will be a showdown between snowray and whoever of the chase pack gains the most; an outcome very close to 99 mm would benefit snowray the most. 

 

 

[snowray]

19 minutes ago, Roger J Smith said:

In the invitation post I mentioned this:

The wettest 30-year average for October was 106.9 mm for 1865-1894, almost matched recently by 106.1 mm for 1986 - 2015 and 1993-2022. The driest 30-year average for October was 77.1 mm for 1946-75. 

Could add that as 1993 total was 94.4 mm, any outcome above 118 mm would make 1994-2023 wetter than 106.9 mm; every 3 mm added to total for 30 years adds 0.1 to average, so to get an increase of 0.8 requires 24 mm more rain in 2023 compared to 1993 as it drops out of total to be averaged.

A total of 137 mm was applied to scoring estimates in contest supporting excel file, and if we get to any outcome 120+ scoring will be similar, snowray (99 mm) manages to hold on to lead in contest, but Reef (131 mm) and Bobd29 close in with higher forecasts and Summer Shower (134 mm) and better scores for October, while current second place Leo97t (80 mm) drops back (if this happens). Leo97t could catch snowray if outcome avoids predicted amounts and stays below 80 mm. Bobd29 (112.5 mm) would be third in that scenario, and between second and fourth at various outcomes between 85 and 125 mm.

If I don't see trends wobbling in next few days, will post preliminary scoring estimates based on the latest outcome from guidance. In any case, the final stage of the contest (Nov 2023) will be a showdown between snowray and whoever of the chase pack gains the most; an outcome very close to 99 mm would benefit snowray the most. 

 

 

Was hoping for somewhere in the 100-110mm range but most likely will be higher now looking at recent model runs, it was looking rather dry for much of the rest of the month just a couple of days ago with the Scandi high moving further west, it just goes to show how quickly things can change,

[Metwatch]

4 hours ago, Weather-history said:

100mm+ Octobers are nothing unusual. It is on average, one of the wettest months of the year.

 

3 hours ago, WYorksWeather said:

Yep, in fact the long term average is just above 100mm.

Average is ~103mm for October yes, but that is the latest 30 year average and in the past it hasn't usually been this high as Roger mentioned.

A look through the EWP data and looks like there has never been 5 consecutive years or more with an October EWP of above 100mm since at least 1765.

There's only been 2 runs of 4 consecutive 100mm Octobers such as

1770 - 1773 and 1777 - 1780

And a few more instances of 3 consecutive 100mm Octobers but that also is still not common.

The last 4 October's EWP:

2019 - 148.8mm

2020 - 164.1mm

2021 - 145.3mm

2022 - 114.0mm

 

Edit: Just looking through the data again, and the last 6 Decembers have had an EWP of above 100mm, that has never happened with any other month before apart from November 1926-1931. Perhaps a 7th this year?

To add: Not sure if this all relates to the changing climate in any way, but if it does, is it something to worry about?

 

Edited October 15, 2023 by Metwatch

[richie3846]

21 minutes ago, snowray said:

Was hoping for somewhere in the 100-110mm range but most likely will be higher now looking at recent model runs, it was looking rather dry for much of the rest of the month just a couple of days ago with the Scandi high moving further west, it just goes to show how quickly things can change,

With rainfall coming up from the south later in the week, we could see some large downpours.

[WYorksWeather]

10 minutes ago, Metwatch said:

 

Average is 102mm for October yes, but that is the latest 30 year average and in the past it hasn't usually been this high as Roger mentioned.

A look through the EWP data and looks like there has never been 5 consecutive years or more with an October EWP of above 100mm since at least 1765.

There's only been 2 runs of 4 consecutive 100mm Octobers as well such as

1770 - 1773 and 1777 - 1780

And a few more instances of 3 consecutive 100mm Octobers but that also is still not common.

The last 4 October's EWP:

2019 - 148.8mm

2020 - 164.1mm

2021 - 145.3mm

2022 - 114.0mm

Edit: Just looking through the data again, and the last 6 Decembers have had an EWP of above 100mm, that has never happened with any other month before apart from November 1926-1931. Perhaps a 7th this year?

 

To be fair I think a lot of these quirks are just statistical coincidences. If we assume the odds of a 100mm+ October are slightly below half if you take a longer term perspective (say 0.4), then the implied probability of five such years in a row is 0.4 ^ 5 or 1%. And of course there are about 250+ groups of five consecutive years to choose from, so you'd expect us to have five in a row at some point, in fact it's probably more surprising that it hasn't already happened.

[Roger J Smith]

As you say, first five consecutive 100+ possible, but I was looking at that potential too and noticed six in a row at 96+ (1820-1825) and another six at 98.6+ (1891-96) so those are fairly close to current streak and roughly on a 70-year cycle that did not repeat around 1960 in a drier period where three wet Octobers would be about the longest stretch (such as 1959-61 and 1966-68).

 

[Summer Sun]

14.1c to the 15th

3.5c above the 61 to 90 average
2.5c above the 81 to 10 average

[Roger J Smith]

... also 2.3 above 1991-2020 average. 

After ten days Oct 2023 was third in running CET but is now t9 with 1825:

 

Top ten first half CET for October

rank __ YEAR ____ 1-15 __ 1-16 (rank) ____ end Oct 

_ 01 ___ 1921 ____ 15.44 _ 15.14 (1) ___ 12.8

_ 02 ___ 1949 ____ 14.95 _ 14.92 (2) ___ 11.7

_ 03 ___ 1959 ____ 14.87 _ 14.73 (3) ___ 12.6

_ 04 ___ 2011 ____ 14.65 _ 14.39 (5) ___ 12.5

_ 05 ___ 1995 ____ 14.49 _ 14.47 (4) ___ 12.8

_ 06 ___ 2001 ____ 14.31 _ 14.14 (8)___ 13.2

_ 07 ___ 1908 ____ 14.22 _ 14.21 (6)___ 11.8

_ 08 ___ 1969 ____ 14.15 _ 14.15 (7) ___ 13.1

_ 09 ___ 1825 ____ 14.09 _ 13.79 (9)___ 10.8

_ 10 ___ 1831 ____ 13.93 _ 13.75 (10)__ 12.7

___________________________________________

various top Octobers not in list

_ xx ___ 2005 ____ 12.94 _ 12.99 ___ 13.0

_ xx ___ 2006 ____ 13.37 _ 13.38 ___ 12.9

_ xx ___ 2022 ____ 12.05 _ 12.03 ___ 12.8

_ xx ___ 1968 ____ 13.28 _ 13.06 ___ 12.5

_ xx ___ 2013 ____ 12.71 _ 12.52 ___ 12.4

_ xx ___ 2014 ____ 11.53 _ 11.65 ___ 12.3

_ xx ___ 1811 ____ 13.27 _ 13.35 ___ 12.3

====================================

Today's GFS guidance suggests an end of October value of 12 C give or take 0.5. EWP is heading for 130 or higher. 

[The PIT]

Sunny Sheffield down to 14.4C +2.0C above average. Rainfall unchanged

[WYorksWeather]

I imagine EWP will be heavily impacted by whether the rain from Storm Babet is focused more over central areas (therefore adding a lot to the E&W total), or more northern areas (adding less since most will hit Scotland).

[Summer Sun]

13.6c to the 16th

3.0c above the 61 to 90 average
2.1c above the 81 to 10 average

[Dancerwithwings]

3 hours ago, Summer Sun said:

13.6c to the 16th

3.0c above the 61 to 90 average
2.1c above the 81 to 10 average

It’s dropping fast now

[ItNeverSnowsInWindsor]

I’m not sure if it’ll make it down to the 11s with a few mild days coming this week. Will take something special to drop  below 12c now.

[damianslaw]

Nothing overly cold on the horizon, indeed near or a little above average, thanks to the cloudy wet conditions holding minima up. Northern parts just outside CET zone will see less in the way of milder weather, average temps.

At this stage a finish in the 12s looks a good bet, but very wide parameters and a late cold snap could pull it down into the 11s, conversely a notable mild end, and we've seen many such instances could see it hold just in the 13s. Either way another above average month on the cards. 

[Addicks Fan 1981]

1 hour ago, prolongedSnowLover said:

I’m not sure if it’ll make it down to the 11s with a few mild days coming this week. Will take something special to drop  below 12c now.

I'm inclined to agree with you on that to be honest and the GFS 12Z tonight doesn't look especially chilly at all really.    

[The PIT]

Sunny Sheffield down to 13.7C, +1.4C above normal. Rainfall unchanged