January 2021 C.E.T. and EWP forecast contests

[The PIT]

Sunny Sheffield at 1.9C -2.5C below average. Rainfall 63mm 77.8% of the monthly average

[Roger J Smith]

EWP update ... 53 mm to 16th and likely also to 17th. GFS ten-day suggests 50-70 mm potential with a bit more after that (28th-31st). Likely to approach 130 mm so have reconfigured the scoring file. Basically some of the higher forecasts made a big move up the tables, most others have just dropped slightly in overall position since my first estimate was already above 80% of the entries. Link to the new version of the scoring file is attached. 

The new annual leader would be shillitocettwo. On this reworked scoring, only three forecasters can gain points, with forecasts higher than 130 mm. Polar Gael (151.3 mm) and John88b (150 mm) already assigned 6th and 7th places for January could move up the annual and January scoring with any outcome above 132 mm. Deep Snow Please (300 mm) can start to move out of the January basement if we reach 163 mm which allows that forecast to outscore 25 mm (Thundershine), currently second lowest. Anyone whose forecast was below 110 mm can only drop two or perhaps three positions in January and maybe one position in the annual scoring as a result. Of course none of this has actually happened yet but as a lot of the heavy precip is due in around Tuesday-Wednesday-Thursday, it seems fairly certain to go well past 100 mm. 

CET appears to be heading for an outcome near 3 C, although still considerable uncertainty about trends beyond a week from today with a week then left in the month. Likely to peak near 3 C by Wed 20th, fall back to near 2.5 by Sunday 24th, and edge back up after that. Corrections could be fairly severe given the possibility of calendar day corrections on top of the usual downward adjustments we seem to get. 

(note: If you downloaded the file before 1700h 18th Jan, it contained an error which is since corrected. Cells P30, Q30 and R30 should not have had values shown but zero instead. This error did not find its way into the scoring columns (they were the scoring adjustments for current Jan leader Moffat in the earlier version). ) Eight downloads of the previous file took place.

 

 

EWP2020_21.xlsx

Edited January 18, 2021 by Roger J Smith

[Summer Sun]

2.6c to the 17th

0.9c below the 61 to 90 average
1.8c below the 81 to 10 average

___________________________

Current high this month 2.6c on the 17th
Current low this month 0.5c on the 1st & 2nd

[Frigid]

I'd say we got 3 days of mild weather ahead of us and possibly a stall in the CET or a slight decrease. Maybe we will get a drop at months end, looks very uncertain

[Roger J Smith]

Back on page 8 I have edited that matrix graph showing possible contenders for top combined forecast.

I have added the range of 2.9 to 3.5 to the chart and moved the target both up (to 2.6) and to the right (130 mm).

Our best combined forecast will likely be a case of best wet forecast and Feb1991Blizzard (5th CET, 17th EWP) and shillitocettwo (at 3.1 C, 105 mm, 23rd and 7th seem to have best chances now, most others in a reasonable CET range will be middle of the pack of EWP, almost all going lower than 80 mm.  Norrance would be close at 16,16. 

Moffat with current best EWP (estimate) has a 4.0 CET forecast and would need the outcome to be about 3.4 or higher to catch up to Shillitocettwo as Feb91Blizzard would be dropping out of contention after about 2.8 C. Reef (3,8 C, 97 mm) might also have a chance especially if the outcomes are very close to his numbers.

Edited January 18, 2021 by Roger J Smith

[Roger J Smith]

12z GFS looked to be a colder run, might justify a downward tick to the end of month estimate to 2.4 after corrections. 

Note -- the February CET/EWP contest thread will appear overnight for your forecasts starting tomorrow. 

Edited January 18, 2021 by Roger J Smith

[The PIT]

Sunny Sheffield at 2.1C -2.3C below normal. Rainfall 70mm 86.4% of the monthly average

[Summer Sun]

2.8c to the 18th

0.7c below the 61 to 90 average
1.6c below the 81 to 10 average

___________________________

Current high this month 2.8c on the 18th
Current low this month 0.5c on the 1st & 2nd

[BornFromTheVoid]

Latest projections and probabilities

 

At the moment, we have 98.8% chance of finishing between 1.5C and 4.5C.

The chances of finishing:
Close to average (3.9 to 4.9C) is  to 29.8% (2 days ago was 32.3%)
Above average (>4.9C) is  to 0.0% (2 days ago was 0.4%)
Below average (<3.9C) is  to 70.2% (2 days ago was 67.3%)

Coldest outcome is above 1C.

[Roger J Smith]

I like that analysis in general, would suggest that the first seven days portion be allowed to end up in a range of uncertainty itself (perhaps 0.5 above and below the mean) and from there the various historical outcomes could be assembled from three or possibly more points, which would have the effect of widening the absolute range of outcomes by 0.5 in both directions. 

From the 06z GFS I would say most likely finish after corrections is still close to 3.0, and the range 2.4 to 3.8 seems to be locking in, but that's not allowing for any past outcomes just the GFS trend with the narrower range of uncertainty derived from the internal perturbation members of the GEFS. Of course in theory the model could be rather wrong at first and extremely wrong later, and any plausible set of January-friendly numbers could be imagined to the end. I would say if for some reason the pattern shifted to record cold after the current storm passes, then the theoretical lower limit of outcomes is about -0.4 (from 21x3 + 10 x --7.5) and the opposite end would be (63+120)/31 = 5.9 C. So we know that without breaking every record every day once Cristoph blows through, the outcome has to be between -0.4 and 5.9. Looks like the historical range is more like within 2-3 of record values in that same interval.

Over in the model thread I posted (about 18h ago now) a table of similar Januaries to the 18th, based on a range of running CET and a cold start; the average outcome of all of them was 3.2 C, and the range about 0.4 to 5.5. The following Febs were all over the place, indicating perhaps a tendency for blocking of some kind to follow a January of this general variety. I noticed that almost all the valid analogues were well back in the past, this current January is acting rather like your stock near-normal January from the late 18th or 19th centuries. Only 2002 and 2009 made it through the relatively wide doors for the analogue set, after 1970, although if I widened them slightly then 1971, 1978 and 1986 also qualified. 

On the EWP front, the current value is likely a bit over 60 mm (to 06z today) with the 06z GFS then adding 45-60 mm from a very regionally divided grid where eastern England gets only 20-30 and some parts of Wales and northern England over 100 mm. That takes us to 06z 29th after which maps suggest one more fairly significant top up in the 10-20 mm range ongoing at end of play.

All told that adds up to 125-150 mm so my earlier provisional for scoring (130) seems okay for now. 

The current value will likely pass 100 mm near the tail end of Cristoph on Friday or so. 

Edited January 19, 2021 by Roger J Smith

[damianslaw]

There has been a fair rise in the CET over recent days, and today is a very mild one, so will be in the 3s tomorrow. The rest of the week looks average in the CET zone possibly a bit below by the end of the week as we see a return to frost. So we are likely to see it stall in the low 3s and a chance might drop back below 3 degrees. Next week looking milder though in the main, so I doubt we can now end up below 3 degrees, the question is where in the 3s will we finish, safe bet probably somewhere in the middle.

The await for a cold January continues, this one had significant potential to be our first proper cold one since 2010, alas looks like ending up fairly average/slightly colder than normal.

[Frigid]

11 minutes ago, damianslaw said:

There has been a fair rise in the CET over recent days, and today is a very mild one, so will be in the 3s tomorrow. The rest of the week looks average in the CET zone possibly a bit below by the end of the week as we see a return to frost. So we are likely to see it stall in the low 3s and a chance might drop back below 3 degrees. Next week looking milder though in the main, so I doubt we can now end up below 3 degrees, the question is where in the 3s will we finish, safe bet probably somewhere in the middle.

The await for a cold January continues, this one had significant potential to be our first proper cold one since 2010, alas looks like ending up fairly average/slightly colder than normal.

Compared to last January, it's been much better. But as you say, yes the latter half of this month has been a disappointment and the CET will probably stall in the low 3s. I just hope, if there even is a chance we finish below 3. Last January CET in the 2s was in 1997. Maybe with corrections or a cold upcoming week, we could get there. 

[The PIT]

Sunny Sheffield zooms up to 2.6C -1.8C below average, Rainfall 86.7mm 107% of the monthly average.

 

[Summer Sun]

3.0c to the 19th

0.5c below the 61 to 90 average
1.4c below the 81 to 10 average

___________________________

Current high this month 3.0c on the 19th
Current low this month 0.5c on the 1st & 2nd

[Roger J Smith]

EWP around 75 mm by 06z today and climbing steadily. It was 62 mm after 18 days and looks to have added 10-15 mm on 19th with heavy rains in Wales and northern England, blended with lesser amounts further southeast. The GFS 10-day projections (from 06z) appear to average 45-50 mm with today's further rainfall a significant part of that, also some at intervals later in the outlook. This average once again is a blend of 100 mm amounts in some parts of Wales and the north, with 30-40 generally for the southeast.

That takes us almost to the end of January where an active system might continue to inflate the totals for the remaining time (estimate 10-15 mm) ... all told that brings the totals to 115-130 mm. Scoring estimate of 130 mm now looking a bit more likely to fall slightly but not enough to make much if any difference to scoring. 

Milder solutions tending to win out recently, CET seems headed for a finish in the 3.2 to 3.6 range after corrections. 

[summer blizzard]

Funnily enough 09 and 13 with the Jan SSW's were also in the low 3C's.

[DAVID SNOW]

6 hours ago, Roger J Smith said:

EWP around 75 mm by 06z today and climbing steadily. It was 62 mm after 18 days and looks to have added 10-15 mm on 19th with heavy rains in Wales and northern England, blended with lesser amounts further southeast. The GFS 10-day projections (from 06z) appear to average 45-50 mm with today's further rainfall a significant part of that, also some at intervals later in the outlook. This average once again is a blend of 100 mm amounts in some parts of Wales and the north, with 30-40 generally for the southeast.

That takes us almost to the end of January where an active system might continue to inflate the totals for the remaining time (estimate 10-15 mm) ... all told that brings the totals to 115-130 mm. Scoring estimate of 130 mm now looking a bit more likely to fall slightly but not enough to make much if any difference to scoring. 

Milder solutions tending to win out recently, CET seems headed for a finish in the 3.2 to 3.6 range after corrections. 

Very wet and rather cool/cold will be the summary of Jan 2021.

Still difficult to pin down exact final numbers, but my best guess would be just under 4c and 120 mm.

See how that holds up with 11 days still to go.

[damianslaw]

5 hours ago, summer blizzard said:

Funnily enough 09 and 13 with the Jan SSW's were also in the low 3C's.

I mentioned the strong similarities with Jan 09 and 21 so far, Jan 09 brought a cold start, the second half of the month was nearer average with some milder and colder interludes, we then had the very cold first 12 days to Feb 09..

Jan 13 was the opposite, a very mild first 12 days, then much colder 2 weeks and a milder end. Feb 13 was episodic with some cold and mild, generally colder later.

Interestingly Dec 08 and Dec 12 shared similarities, cold first halves then much milder, though in 2008 mild was shorter lived with a cold end - hallmarks with Dec 20. 

[Frigid]

35 minutes ago, damianslaw said:

I mentioned the strong similarities with Jan 09 and 21 so far, Jan 09 brought a cold start, the second half of the month was nearer average with some milder and colder interludes, we then had the very cold first 12 days to Feb 09..

Jan 13 was the opposite, a very mild first 12 days, then much colder 2 weeks and a milder end. Feb 13 was episodic with some cold and mild, generally colder later.

Interestingly Dec 08 and Dec 12 shared similarities, cold first halves then much milder, though in 2008 mild was shorter lived with a cold end - hallmarks with Dec 20. 

I feel like winter 2020/21 is a teaser for something much better next year. Time will tell

[damianslaw]

48 minutes ago, Frigid said:

I feel like winter 2020/21 is a teaser for something much better next year. Time will tell

As happened in winter 09-10. Hope so.

[Don]

5 minutes ago, damianslaw said:

As happened in winter 09-10. Hope so.

Could be and hopefully COVID will be under control by then too!  Colder winters do tend to come in clusters and whilst 2020/21 has not been particularly cold so far, it is synoptically very different to the vast majority of winters since 2012/13!

[The PIT]

Sunny Sheffield at 2.7C -1.7C below average, Rainfall 111.7mm 137.9% of the monthly total.

Edited January 21, 2021 by The PIT

[Roger J Smith]

EWP update ... my estimate for 19th (13 mm) was correct and the map for 20th looks very similar so now we have probably jumped up to around 88 or 90 mm. The ten-day GFS estimate looks to be in the 40 mm range and a bit more would fall on the 31st so we're still good with the 130 mm scoring estimates. 

If anything, latest guidance is very slightly colder during the milder days after Monday when the coming cool spell begins to fade out ... that provides a new estimate of 2.9 to 3.4 as landing zone for CET. Good to see a January that isn't 5 or 6 point something anyway. 

[Froze were the Days]

12 hours ago, damianslaw said:

I mentioned the strong similarities with Jan 09 and 21 so far, Jan 09 brought a cold start, the second half of the month was nearer average with some milder and colder interludes, we then had the very cold first 12 days to Feb 09..

Jan 13 was the opposite, a very mild first 12 days, then much colder 2 weeks and a milder end. Feb 13 was episodic with some cold and mild, generally colder later.

Interestingly Dec 08 and Dec 12 shared similarities, cold first halves then much milder, though in 2008 mild was shorter lived with a cold end - hallmarks with Dec 20. 

Still struggling to get that first -1c anomaly for a winter month on the 1961-90 CET series for over a decade now!...

[Summer Sun]

3.3c to the 20th

0.2c below the 61 to 90 average
1.2c below the 81 to 10 average

___________________________

Current high this month 3.3c on the 20th
Current low this month 0.5c on the 1st & 2nd