September 2023 C.E.T. and EWP forecast contests

[Summer Sun]

18.3c to the 20th

4.7c above the 61 to 90 average
3.8c above the 81 to 10 average

[Summer8906]

I'm hoping this month does not break any records, to be honest. It would be a shame if a month with such a poor second half took the record due to a freakish heatwave early on. I'd much prefer a record warm September to be one dominated by anticyclonic conditions.

It's similar thinking to to how I was disappointed when that brief heat spike took the UK all time heat record in 2019; it didn't seem "worthy" of the record, if you know what I mean. The record being set again in summer 2022 during a prolonged fine period was thus a relief.

One record this month will take, perhaps, is "biggest and most disappointing come down after a promising start". December 2022 is another example, but I think this month has trumped it.

Edited September 21, 2023 by Summer8906

[Frigid]

Looks like the heat signal for the end of the month has faded away somewhat. Curious to know what the CET could be, perhaps mid to upper 16s. No chance of going below 16C. 

[summer blizzard]

1 hour ago, Summer8906 said:

I'm hoping this month does not break any records, to be honest. It would be a shame if a month with such a poor second half took the record due to a freakish heatwave early on. I'd much prefer a record warm September to be one dominated by anticyclonic conditions.

It's similar thinking to to how I was disappointed when that brief heat spike took the UK all time heat record in 2019; it didn't seem "worthy" of the record, if you know what I mean. The record being set again in summer 2022 during a prolonged fine period was thus a relief.

One record this month will take, perhaps, is "biggest and most disappointing come down after a promising start". December 2022 is another example, but I think this month has trumped it.

We were solid from the 29th Nov-18th Dec so that's a solid two thirds. 

[Don]

2 hours ago, Frigid said:

Looks like the heat signal for the end of the month has faded away somewhat. Curious to know what the CET could be, perhaps mid to upper 16s. No chance of going below 16C. 

Nope, September cannot be saved now! 

[The PIT]

Sunny Sheffield down to 17.7C +2.8C above normal. Rainfall 65.2mm 99.1% of the monthly average.

[Summer Sun]

18.1c to the 21st

4.5c above the 61 to 90 average
3.7c above the 81 to 10 average

[damianslaw]

Looking a close call whether we see the warmest Sept on record and also whether we beat June this year. 

We have a cooler interlude now, but the rest of the month looks mild largely thanks to unsettled windy weather keeping mins up. SE parts holding onto some warmth.

Further north and west closer to average, but still a little above late Sept mean.

[poleup]

22 hours ago, Summer8906 said:

I'm hoping this month does not break any records, to be honest. It would be a shame if a month with such a poor second half took the record due to a freakish heatwave early on. I'd much prefer a record warm September to be one dominated by anticyclonic conditions.

It's similar thinking to to how I was disappointed when that brief heat spike took the UK all time heat record in 2019; it didn't seem "worthy" of the record, if you know what I mean. The record being set again in summer 2022 during a prolonged fine period was thus a relief.

One record this month will take, perhaps, is "biggest and most disappointing come down after a promising start". December 2022 is another example, but I think this month has trumped it.

 

  aviator-fun

 

 

 

 

 

Of course, it's too early to say for sure. However, the current forecast suggests it's possible. If it does happen, I hope it's for a more worthy reason than the heat wave to begin with.

[Derecho]

22 hours ago, Frigid said:

Looks like the heat signal for the end of the month has faded away somewhat. Curious to know what the CET could be, perhaps mid to upper 16s. No chance of going below 16C. 

Indeed, it won't drop below 16C. The EC has us just short of the record at 16.8C, both the control and the OP.

GFS OP and control are both slightly cooler and end at 16.6C.

Good agreement on some above average temperatures between the 24th and 26th. Whether any warm persists after that is key to a record breaking September.

Personally I don't think it will happen. The EC is on the warmer side of the ensembles with the key point coming after the 26th.

[Roger J Smith]

Yesterday's CET average of 13.2 preserves for 1949 its distinction of recording the highest value for low daily average, 13.3. 

[Earthshine]

How are we looking for beating the old maximum CET record of 20.9C for September?  Starting to plummet a bit now but still 22.8C.  Could be in for a good chance!

[Don]

4 hours ago, damianslaw said:

Looking a close call whether we see the warmest Sept on record and also whether we beat June this year. 

Whether it's the warmest September on record or not, it's still going to be a case of hoping that we get a 'first time for everything' this coming winter!

[Roger J Smith]

The legacy of this Sep will perhaps be the very high SST values around Britain and that will add vigour to fall cyclones as well as eventually adding potential for snow in any winter easterly outbreaks. I believe there will be a few, looking at the variable trends this past season. Also our moon is at its greatest declination range (29 deg) and that was identified in 20th century research as a positive factor in blocking patterns. Recent peaks of range were 1950, 1969, 1987 and 2006, all winters with cold synoptics along with milder spells. Expect a bit of a wild ride for winter 2023-24, don't believe it will be a bland winter but variable in nature. 

[The PIT]

Sunny Sheffield down to 17.4C +2.6C above normal. Rainfall up to 65.6mm 99.7% of the monthly average.

[damianslaw]

19 hours ago, Roger J Smith said:

The legacy of this Sep will perhaps be the very high SST values around Britain and that will add vigour to fall cyclones as well as eventually adding potential for snow in any winter easterly outbreaks. I believe there will be a few, looking at the variable trends this past season. Also our moon is at its greatest declination range (29 deg) and that was identified in 20th century research as a positive factor in blocking patterns. Recent peaks of range were 1950, 1969, 1987 and 2006, all winters with cold synoptics along with milder spells. Expect a bit of a wild ride for winter 2023-24, don't believe it will be a bland winter but variable in nature. 

Lunar influence is a whole science in itself and there are some who value it as a key factor in influencing the weather. Interesting to note the 18-19 year pattern, though I assume mean winter 86-87 rather than 87-88 which would be 17 years different. Is the post above from a Canada perspective?

Back to the CET, trending less mild than expected rest of the month but still a bit above average under a predominantly south - west flow. The cloudy wet conditions will supress maxes somewhat but keep mins up. 

 

[Don]

6 minutes ago, damianslaw said:

Back to the CET, trending less mild than expected rest of the month but still a bit above average under a predominantly south - west flow. The cloudy wet conditions will supress maxes somewhat but keep mins up. 

 

Yes, cold nights are required to properly dent the CET.

[Roger J Smith]

1 hour ago, damianslaw said:

Lunar influence is a whole science in itself and there are some who value it as a key factor in influencing the weather. Interesting to note the 18-19 year pattern, though I assume mean winter 86-87 rather than 87-88 which would be 17 years different. Is the post above from a Canada perspective?

Back to the CET, trending less mild than expected rest of the month but still a bit above average under a predominantly south - west flow. The cloudy wet conditions will supress maxes somewhat but keep mins up. 

 

The exact timing of the lunar declination cycle is 18.6 years and peaks were 1950.2, 1968.8, 1987.4, 2006.0 and next one around 2024.6. My comments were about colder UK winters. Research shows that when the moon's range of declination exceeds 27 deg (which is about a 5-6 year interval surrounding those peaks) blocking is enhanced, and when the opposite occurs between peaks, zonal flow is favoured. Last peak of favoured zonal flow was around winters of 2013-14 to 2016-17, before that, late 1990s. In terms of correlation with North America, a better correlation exists with western North America and Europe, winter anomalies tend to run opposite phase to some extent when comparing eastern NA and western Europe (and that is not something governed by any one influence). 

(non-weather content follows, skip reading this unless interested in lunar orbital details)

In case anyone reading is interested in knowing why there is a lunar declination cycle, the basic reason is that the Moon orbits the earth in the ecliptic plane rather than around our equator, but has a fast-shifting 5.1 deg inclination to that plane. If there were no inclination, we would get solar and lunar eclipses at every full and new moon. But the 5.1 deg inclination is then added to, or subtracted from, sun's apparent declination in our skies, on a monthly cycle that runs just a bit faster than the 27.32166 days that it takes the Moon to complete an orbit relative to the fixed star background. The Sun is moving slowly forward against that so it takes 29.53 days for the Moon to complete an orbit relative to Sun's position. Each month, the nodes of the orbit crossing the ecliptic retogress back along the ecliptic slightly, and this causes the northern and southern latitude maxima to be positioned slightly earlier in each succeeding orbit. Right now, they are just a bit after the Sun's seasonal declination maxima (23.4 deg N and S) which are fixed against the calendar year at summer and winter solstice. So this coming winter, peak lunar declinations will be around where the Sun was in late June and early July, plus five degrees. The winter minima of full moon declinations will be around where the Sun is then located near end of Dec and start of Jan, minus five degrees. The timing of 2024.6 means that the following winter will see the peaks corresponding to solar positions in mid-June and mid-December. It will be during summer 2024 that the absolute largest declination ranges will occur. 

Obviously the moon will be well displaced from the Sun's position at summer and winter full/new moons and will cross the solar track along the ecliptic at times favourable to eclipses in October and April forthcoming (there's an annular solar eclipse about to happen in Oct 2023 south of my location, and a total eclipse across the south-central U.S. on April 8th, 2024). This is also why the timetable of eclipses shows two tendencies : first, eclipses happen about every 5-6 months in groups, and therefore about a month earlier each successive year (it would be more like 12/18.6 of a month earlier each year or about 20 days). It also explains why similar solar eclipses occur every 19 years but only for limited times until the differential between 18.6 and 19.0 removes the repeating tendency and introduces a new set. By similar, I mean similar as to date and track orientation, the longitudes will vary considerably placing these eclipses in different regions of the world. Lunar calendars are similar every 19 years, I think it takes about four or five centuries to move full and new moon dates a couple of days forward, but position relative to leap year cycles will prevent the 19 year lunar similarity to becoming fixed to exact dates. Basically, if five leap years fall between two dates 19 years apart, the Moon will reach its full and new phases at similar if not exactly the same dates and times, but if there are only four leap years then the timing will be about one day later on the calendar after 19 years. As there are more of the former cases (five leap years) the general pattern over 76 years is for long intervals of dates being similar to dates 19 years previous, followed by intervals of dates that are about one day later than 19 years previous. All of this can be a bit complicated by the effects of moving lunar perigee altering the speed of the Moon in orbit so it can reach full or new moon a bit earlier or later than a fixed schedule would imply. The most recent occasion with four leap years intervening in 19 years would be (1 Mar 2004 to 28 Feb 2005) to (1 Mar 2023 to 28 Feb 2024), and as expected later dates occur for the current interval than in 2004-05, for example, the November new moon was on 12th in 2004, and 13th in 2023. Almost identical dates and times then resume in March 2024 after the 29 Feb 2024 leap year day restores an interval of five intervening. That lasts until 1 Mar 2027 but you can see the effects of lunar perigee and possibly other second-order orbital effects for the earth in the solar system, distorting the exact replication as times creep earlier in 2025-26 relative to 2006-07, after very similar times in 2024 compared to 2005; the differential for new moons reaches about 12 hours early by mid to late 2026 and that remains the case to the next leap year date interruption in Mar 2027, so that calendar comparative dates then shift from one half day early to one half day late, and this persists to the reset in March 2028 and through most of 2028. Dates and times for 2029 compared to 2010 become more similar with the offset only two hours by late 2029. By mid-2030 times are a few hours earlier than for 2011, and then creep back to parity just before the next one-day shift in March 2031. By 2400 AD all comparisons with 380 years (20 x 19) previous will have shifted about two days forward. The removal of leap years from three out of four centuries tends to accelerate this drift forward until the century with the added leap year. If there were 29th of Febs in 2100, 2200 and 2300 (there will not be), then dates in 2400 would be shifted three days earlier and the two day later phenomenon would change to one day earlier. So until after 29 Feb 2400, there will be a slight tendency for the 19 year comparisons to drift forward at about one day per century, pausing the forward drift by the 25th century. The extra leap year in 2400 will reset the entire system to times more similar to the century then ending.

What that all means to lunar calendar comparisons would be that every 76 years, dates would shift almost a full day forward, in cases where missing leap year days intervened, so 2024 to 2100 would shift forward after 1 Mar 2100 (29 Feb 2100 will not occur), dates would be similar 2176 to 2100, another shift forward would happen 2252 compared to 2176 (2200 intervenes), and also another shift forward 2328 compared to 2252 (2300 intervenes), but 2328 would be more similar to 2404 (while 2400 intervenes, it has the added leap year day to prevent a forward shift for 2404). 

The math of this is clear enough ... 76 years = 27759 days with all leap years counting, 27758 when one (e.g. 2100 AD) is not counting. 940.01 lunar cycles in 27759 days, 938.98 in 27758 days.

With no missing leap years, 760 years would take 9400.1 lunar cycles; 0.1 lunar cycle equates to about 3 days so after 760 years moon would be reaching full or new dates 3 days earlier, however in that 760 years, six or seven leap years will be dropped from calendars, so that will change the 3 days earlier to 3 or 4 days later. 

[Roger J Smith]

No Hadley CET updates showing yet, would estimate that yesterday's mean was around 12 C and the running CET is therefore around 17.8. 

The EWP was last spotted at around 73 mm and GFS gives another 15-20 on average (quite dry in southeast, wet in parts of Wales and nw England, but grid average is not much over 15 mm). Our scoring estimate table seems safe enough at this point. 

The output for CET rest of the way appears to settle at about 16.7 or 16.8, so GFS says no record for you. Odds are probably a bit less than 1 in 3 chance now, it's not carved in stone either way. In any case, for CET scoring it only affects a few outcomes as to where this lands, anyone below 16.2 is probably going to score the same no matter what the value actually is, the flow is such that I think we can rule out a finish below 16.5 now. 

[Shillitocettwo]

1 hour ago, Roger J Smith said:

No Hadley CET updates showing yet, would estimate that yesterday's mean was around 12 C and the running CET is therefore around 17.8. 

The EWP was last spotted at around 73 mm and GFS gives another 15-20 on average (quite dry in southeast, wet in parts of Wales and nw England, but grid average is not much over 15 mm). Our scoring estimate table seems safe enough at this point. 

The output for CET rest of the way appears to settle at about 16.7 or 16.8, so GFS says no record for you. Odds are probably a bit less than 1 in 3 chance now, it's not carved in stone either way. In any case, for CET scoring it only affects a few outcomes as to where this lands, anyone below 16.2 is probably going to score the same no matter what the value actually is, the flow is such that I think we can rule out a finish below 16.5 now. 

In a way I don't think this September actually deserves the CET record warmth title, an exceptionally third should not be sufficient to carry a very average two thirds!

[Don]

5 hours ago, Roger J Smith said:

rule out a finish below 16.5 now. 

This will make winter evermore intriguing!  

[Derecho]

11 minutes ago, Don said:

This will make winter evermore intriguing!  

I don't think it really matters. The weather during September doesn't affect the weather during winter.

[Dancerwithwings]

18 minutes ago, Derecho said:

I don't think it really matters. The weather during September doesn't affect the weather during winter.

Absolutely 10 days is pushing it

 I’m sure Don was thinking lightly

[The PIT]

Sunny Sheffield down to 17.2C +2.4C above average, Rainfall 66.1mm 100.5% of the monthly average.

I think our new record is safe needs to lose another degree to fail to create a new record.

Edited September 24, 2023 by The PIT

[Don]

11 hours ago, Derecho said:

I don't think it really matters. The weather during September doesn't affect the weather during winter.

Well, until we get a cold winter following a very warm September, this will continue to be debated!  However, nothing wrong with that of course.

11 hours ago, Dancerwithwings said:

Absolutely 10 days is pushing it

 I’m sure Don was thinking lightly

Like I said, an intriguing winter season coming up and not only because of the warm September.  No thinking lightly from me!