December 2023 C.E.T. and EWP forecast contests -- start of 2023-24 contest year -- all welcome

[damianslaw]

A cold day in the CET zone today will likely result in a drop tomorrow recordings, then a marked rise for at least a week and possibly more. Quite probably will be close to average by mid month... 

[LetItSnow!]

If the signal of a surface cold high for the middle of December comes to fruition then perhaps a tick down again after the mild spell. I still think it’s all to play for - perhaps less chance of anything extreme now though. 

This month is reminding me of December 2020 a little bit when after a cold first week or so, then it turned mild and unsettled mid-month. I wonder if we’ll see another see-saw like that month…

[Summer Sun]

1.9c to the 6th

2.6c below the 61 to 90 average
3.7c below the 81 to 10 average

[Metwatch]

Quite a steep rise on the EWP for the first 5 days, up to 32mm.

 

Current wetter than average spell looks to last until early next week. An extra 40mm ish to be added to give an EWP total of around 70mm, ± 5mm by around next Thursday, before high pressure likely arrives and turns things a lot drier.

CET as Damian mentioned above probably returning quickly to average next week, but if the high pressure later next week makes it colder at the surface, may not see too much of a rise.

Edited December 7, 2023 by Metwatch

[The PIT]

Sunny Sheffield up to 0.9C -5.7C below average. Rainfall 38.1mm 43.5% of the monthly average.

[Roger J Smith]

I agree on EWP, my estimate is 45 mm to present time and 75-85 would be total by 23rd according to GFS (quite dry after 14th). I just posted in the Nov thread what that all means for annual totals and ranking of 2023, basically it suggests we are going to end up between 12th and 8th wettest year depending on what happens after the 23rd. 

For the CET, the cold start may be enough to overcome the milder trend for the next five or six days, as it then turns quite cold again for at least a week; my estimate is that CET will gradually rise to about 4.5 to 5.0 C at some point around a week from now, but will then drift back down towards 4 C as several days will only produce means of 1 to 3 C and at no point does it warm up again beyond about 4 or 5 C. Again, what happens from 24th to 31st, if all of that were accurate, would determine the fate of our forecasts, it could just as easily soar back up towards 5 or even 6 C, or drop down further towards the lowest forecasts we made in the 2 to 3 range. I was expecting a major energy peak around 25-27 Dec and again, if that occurs, it would be a wintry mix if we stay in a cold pattern, or a rain and wind event in a warmer turn. 

I would say odds of this now turning out as warmest year (it needs to be a 7.6 C Dec) are very long odds now, maybe a 1 in 20, and odds of all 12 months being above 1961-90 normals is a bit below a 50-50 proposition if not right on 50-50. (4.7 is needed for that, I think). If the GFS is correct, the last week would need to average above record high values of 11-12 C to get to 7.6, but would only need to average about 5.5 to 6.0 to get to 4.7, and that has often been the case in recent years with a tendency for higher values in the holiday period than earlier. 

[WYorksWeather]

2 hours ago, Roger J Smith said:

I agree on EWP, my estimate is 45 mm to present time and 75-85 would be total by 23rd according to GFS (quite dry after 14th). I just posted in the Nov thread what that all means for annual totals and ranking of 2023, basically it suggests we are going to end up between 12th and 8th wettest year depending on what happens after the 23rd. 

For the CET, the cold start may be enough to overcome the milder trend for the next five or six days, as it then turns quite cold again for at least a week; my estimate is that CET will gradually rise to about 4.5 to 5.0 C at some point around a week from now, but will then drift back down towards 4 C as several days will only produce means of 1 to 3 C and at no point does it warm up again beyond about 4 or 5 C. Again, what happens from 24th to 31st, if all of that were accurate, would determine the fate of our forecasts, it could just as easily soar back up towards 5 or even 6 C, or drop down further towards the lowest forecasts we made in the 2 to 3 range. I was expecting a major energy peak around 25-27 Dec and again, if that occurs, it would be a wintry mix if we stay in a cold pattern, or a rain and wind event in a warmer turn. 

I would say odds of this now turning out as warmest year (it needs to be a 7.6 C Dec) are very long odds now, maybe a 1 in 20, and odds of all 12 months being above 1961-90 normals is a bit below a 50-50 proposition if not right on 50-50. (4.7 is needed for that, I think). If the GFS is correct, the last week would need to average above record high values of 11-12 C to get to 7.6, but would only need to average about 5.5 to 6.0 to get to 4.7, and that has often been the case in recent years with a tendency for higher values in the holiday period than earlier. 

Just thinking about this. We're on 1.9C to the 6th. if the next six days were to average say 8C (which looks possible - tomorrow and Friday a bit cooler than that, but Saturday to Tuesday does look very mild), then we'd be at near 5C as you suggested.

I also think that as a rule, the GFS has a tendency to slightly under-read temperatures. Therefore, if it looks quite close, I'd probably err on the side of thinking it'll come out on the milder side. I'm not looking much past early next week though, to be honest.

[WYorksWeather]

Might as well post my average-based forecast from the other thread.

Update based on data up to 6th December

Today's average: 1.9C (6 days)

10-year average for rest of December: (1.9 * 6 + 5.9 * 25) / 31 = 5.1C

30-year average:  (1.9 * 6 + 4.9 * 25) / 31 = 4.3C

[Summer Sun]

2.2c to the 7th

2.3c below the 61 to 90 average
3.3c below the 81 to 10 average

[The PIT]

Sunny Sheffield up to 1.1C -5.5C below average. Rainfall up to 54.8mm 62.6% of the monthly average.

[ItNeverSnowsInWindsor]

Game over for my guess with the mild weather!

[The PIT]

Sunny Sheffield up to 1.7C -4.7C below average. Rainfall 59.4mm 67.9% of the monthly average.

[Summer Sun]

2.9c to the 8th

1.7c below the 61 to 90 average
2.4c below the 81 to 10 average

[Roger J Smith]

Current projection to 25 Dec is around 4 to 4.5 C, a cold week expected to follow a relatively mild one. EWP projection is around 85-95 mm. 

[Summer Sun]

3.6c to the 9th

1.0c below the 61 to 90 average
1.6c below the 81 to 10 average

[damianslaw]

Only going up and up, could well be comfortably in the 5s in a week's time. 

[kold weather]

Models all have the same broad pattern but the GFS keeps the high close enough to allow for some homegrown cold to develop, the ECM meanwhile keeps it just far enough away that we import, particularly the further west and north you go. 

Therefore its best not to weigh too much onto any one particular model solution at the moment, since the GFS comes in considerably colder than the ECM would.

[Summer Sun]

4.1c to the 10th

0.5c below the 61 to 90 average
1.0c below the 81 to 10 average

[snowray]

Made a little calculation to the 10th and came up with 4.04c, not too far off.

[Roger J Smith]

EWP at about 70 mm and after another 10 or so by late Tuesday, looks to add only about 10 additional by 27th as trends go dry for a change. 

CET projection (GFS) is a gradual rise to 18 Dec to reach about 5.5, followed by a slump back to starting point of 4 C, but the rise is probably higher confidence than the later fall. So all bets from 4 to 6 C are probably in play. Personally I don't trust this current run and figure we will get into a more active pattern after 20 Dec. 

 

[The PIT]

Sunny Sheffield up to 3C -3.3C below average. Rainfall 86.5mm 98.9% of the monthly average.

[Summer Sun]

4.4c to the 11th

0.1c below the 61 to 90 average
0.6c below the 81 to 10 average

[The PIT]

Sunny Sheffield up to 3.4C -2.8C below average. Rainfall up to 90.6mm 103.5% of the monthly average.

[Don]

Thinking my 5.4C guess 'could' be on shaky ground!

[LetItSnow!]

My 2.8C degree guess absolutely toast