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

[Frigid]

First 7 days of May 1996 had a provisional CET of 7.1c, so it's been the coldest first week of May for 25 years. I still think my 10.8 is safe, temperatures look average over the next week or so...

[damianslaw]

38 minutes ago, Frigid said:

First 7 days of May 1996 had a provisional CET of 7.1c, so it's been the coldest first week of May for 25 years. I still think my 10.8 is safe, temperatures look average over the next week or so...

Not surprised coldest start since 1996, growth has been stunted all week. 1996 stayed cold until the very latter stages, many days with maxima in the 8-10 degrees range under a cold cloudy NE airstream. There was a marked change to very warm at the tail end of the month, lasting through early June - it was a major shock after a generally long cold period.

 

[Roger J Smith]

EWP is probably close to 40 mm, it had reached 23 mm by 6th and the 24h amount to 06z 7th appears to be 10-12 mm, then since I'm using the 12z GFS for its projection, I need to estimate rainfall 06z-12z that fell between the two amounts, that could be 3-5 mm as the heavy rain band moved north earlier today ... and the ten day projection is a solid 30 mm over the grid with a few areas up to 50 mm, taking the lower value the total is 23+11+4+30 = 68 mm by the 18th (06z), and maps for 18th to 24th appear fairly juicy too so could be as high as 80-90 mm by the 24th. Predictions around 100 mm may not be too far off at that rate. One thing about going high is that you have a bit of a comfort zone, where I went there's nobody within 10 mm on either side, just one forecast higher by quite a bit so I have 20 mm room on the upside, problem is to get into that range though.

Would say the CET will average about 12 C through the sixteen days, Sunday-Monday look fairly warm, rest of next week a bit below average at times, then up and down around normal, anyway 7.2 to the 8th and 12 average for sixteen days would give an average of 10.4 by the 24th which as some have said would make predictions near 11 C a good bet. 

[Frigid]

26 minutes ago, damianslaw said:

Not surprised coldest start since 1996, growth has been stunted all week. 1996 stayed cold until the very latter stages, many days with maxima in the 8-10 degrees range under a cold cloudy NE airstream. There was a marked change to very warm at the tail end of the month, lasting through early June - it was a major shock after a generally long cold period.

 

Wish I was alive to witness it, must've been very bizarre. Similar situations I can recall is that mini heatwave late May 2012 and July 2013 where cooler periods preceded them.

[SummerShower]

2 hours ago, Frigid said:

Wish I was alive to witness it, must've been very bizarre. Similar situations I can recall is that mini heatwave late May 2012 and July 2013 where cooler periods preceded them.

I remember 1996 and it was definitely the worst may I remember, certainly worse than say 2007, 2nd half of 2008 and 13/15.  The first 7 days of this month have had that may 96 kind of feel to it.  That year was especially cold mid month, if I remember there was snow on Dartmoor around 18th.  It turned westerly after that albeit with at best average temperatures, but then there was a sudden flip to hot after 29th.

If that hot spell at the end hadn't have happened I think may 96 would have been in the 8s! 

This year, though may could well be cold, I can't see it being anywhere near 96 levels.  Maybe 2010/2013 levels..

If we get any sudden warm ups, with the SSTs cold, we could get some decent thunderstorms at some point..

 

Edited May 8, 2021 by SummerShower

[The PIT]

Sunny Sheffield up to 6.8C -2.8C below normal. Rainfall up to 64.7mm 108.6% of the monthly average.

So passed average rainfall already got to be a chance of another month reaching 100mm which should bring Spring to closer to average values rainfall wise.

[damianslaw]

47 minutes ago, The PIT said:

Sunny Sheffield up to 6.8C -2.8C below normal. Rainfall up to 64.7mm 108.6% of the monthly average.

So passed average rainfall already got to be a chance of another month reaching 100mm which should bring Spring to closer to average values rainfall wise.

May certainly looks like making up for the very dry April. A very wet May looking highly probable..

Wet May's have followed dry April's in 1987, 2007 and 2011... following summers were also wet!

[Summer Sun]

7.4c to the 8th

2.7c below the 61 to 90 average
3.3c below the 81 to 10 average

___________________________

Current high this month 7.4c on the 4th and 8th
Current low this month 6.6c on the 1st

[Roger J Smith]

I worked out the EWP projection earlier and from the 06z GFS, it looked like it had increased to near 50 mm after yesterday, so the 25 mm average on the 10-day brought that to 75 mm and 20-25 mm appeared plausible for days 11-16, total near 100 mm by 25th. Just checked the 12z GFS and same general idea although a heavier local max over the west Midlands - Severn valley where 75 mm could fall apparently. CET estimate would still be mid to high 10s by 25th from either run. ECM looks marginally cooler through first ten days. I feel that low 10s are pretty much guaranteed at some point, but how far into the 10s? After adjustments, almost any outcome seems possible so 10.5 is probably the over/under at this point in time. 

[Roger J Smith]

Our CET consensus was 11.1 but the predictions were rather "bimodal" this month with two peaks, one around 11.5 and the other one around 10.7, those two choices each had five backers and in each case there were four more punts on the inside flank at 11.4 and 10.8. There were another four at each spot above 10.8 to 11.0, then there are only seven in total from 11.1 to 11.3 near consensus, so it looks like we had two camps in terms of either a fairly fast breakdown of cold or a lingering cool theme. Scoring for the CET is going to be very tight this month, you could be within 0.5 and halfway down the table.  With most of the colder forecasts being quite high on EWP also, it's going to take me a while at the end to determine best combined, I won't be speculating much because half the field are probably in with a chance. The EWP forecasts are also bunched a little near the median but it opens out towards the apparent landing zone which right now looks to me like being low 100s to 120. 

[The PIT]

Sunny Sheffield up to 7.3C -2.4C below average. Rainfall 64.7mm 108.6% of the monthly average.

[Roger J Smith]

Not even a third of the way into May and already four times the April rainfall with similar amounts expected in the next two thirds. If anything the EWP estimate is now higher than before, we are at about 45 mm now and look to double that by 20th, with further rainfalls depicted days 11 to 16, at least 15 and possibly 25-30 mm more (and the month not quite done) so that's a total near 110 mm and counting. In 255 previous Mays, we have had 26 that reached 100 mm and nine that reached 120 mm (the max is 151.8 mm from 1783, then 1782 is second so that 1967 in third (140.7 mm) is the only one anyone here would possibly recall, I know that was a very chilly month in eastern North America although not unusually wet, after a warmish April, which is sort of how this spring is also going so far. More recently, 2007 was 11th wettest (just below 120 mm) and 2006 was 16th wettest. Most of the top 20 wet Mays were before even the oldest of us were alive. 2006 and 1983 in the list is encouraging, otherwise the list of the top 20 does not sound like much of a template for good summers apart from those and 1797 possibly ... this is the list in order (without the amounts which tend to drop off fairly regularly anyway) ...

1773 _ 1782 _ 1967 _ 1932 _ 1843 _ 1886 _ 1924 _ 1811 _ 1869 _ 1979 _ 2007 _ 1878 _ 1969 _ 1983 _ 1807 _ 2006 _ 1796 _ 1813 _ 1797 _ 1766

Before 2007, the closest I could find to a very dry April followed by a very wet May was 25th driest April 1807 followed by 15th wettest May 1807. (22.9 to 113.9 mm)

Second driest April 1817 (7.9 mm) was followed by 101.4 mm in May. 1796 was in the ball park also. So here's a bit of an indication that a weather pattern that showed up in the Dalton minimum is now perhaps showing up in this solar downturn (not really that strong a finding but Fred's going to like it). 

Edited May 10, 2021 by Roger J Smith

[BornFromTheVoid]

Latest projections

 

The chances of finishing:
Close to average (11.4C to 12.4C) is  to 18.5% (3 days ago was 21.7%)
Above average (>12.4C) is  to 0.4% (3 days ago was 1.6%)
Below average (<11.4C) is to 81.1% (3 days ago was 76.7%)

The period of the 10th to the 15th is forecast to average 10.7C, 0.6C below the 91-20 average.

[Summer Sun]

8.0c to the 9th

2.1c below the 61 to 90 average
2.7c below the 81 to 10 average

___________________________

Current high this month 8.0c on the 9th
Current low this month 6.6c on the 1st

Edited May 10, 2021 by Summer Sun

[The PIT]

Sunny Sheffield up to 7.8C -2.0C below normal. Rainfall 68.5mm 114.9% of the monthly average

[Summer Sun]

8.4c to the 10th

1.7c below the 61 to 90 average
2.3c below the 81 to 10 average

___________________________

Current high this month 8.4c on the 10th
Current low this month 6.6c on the 1st

[Roger J Smith]

EWP has reached 50 mm (46 to 9th, approx 4 mm yesterday) and the 12z GFS run shows a solid 40-50 mm average rainfall in the next ten days with maps for days 11-16 showing two rainfall events in the 10-15 mm range (each) so that all adds up to Roger J Smith 110-130 mm (sorry getting carried away there, my fcst 127.2, only one went higher, shil said 168), 110-130 mm. And that's by 27th, could go higher 28th to 31st. If it reaches 120 mm the only score in doubt will be shillitocettwo whose error at that point would be near middle of the pack (equal to 72 mm which is just below consensus), that score would go up quite rapidly with every additional mm, 148 mm required for the win. davehsug at 109 mm has a safety zone of 105.2 to 118.1 mm, coldest winter at 101.3 mm has 101-Don cutting off his comfort zone but still commands the domain 101.2 to 105.1 mm. DR(S)NO is at 100 mm and IRemAtl252 at 98 mm. 

Looks like a rather cool pattern almost throughout, the odd day gets to near normal, will be a slow climb towards 10 C now and will we break through? Remains to be seen, especially in terms of an adjusted final value, think it's more likely than not but over-under has probably shifted down to around 10.3 C. (Kentish Man and Daniel are on that, Relativistic and Walsall Wood Snow are at 10.4 while B87 and coldest winter are at 10.2 ... obviously a bit early to be calling favourites yet but these are closest to my estimate for what little that may be worth (the EWP projection has the advantage of being unable to go in either direction so if it looks wet then it has to keep going up by some amounts anyway). 

[summer blizzard]

Coolest opening third since 2010 (joint).

[Shillitocettwo]

I remember May 1996, seemed cool and overcast for most of it. 

[The PIT]

Sunny Sheffield up to 8C -2.0C below average. Rainfall 83.7mm 140.4% of the monthly average.

[Weather-history]

April-May CET combinations

2013 CET: 8.95C  (A May CET < 11.5C will beat this)

1996 CET: 8.8C (A May CET < 11.2C will beat this)

1986 CET: 8.45C (A May CET < 10.5C will beat this)

1941: CET: 7.9C (A May CET <9.4C will beat this)

 

 

[Summer Sun]

8.6c to the 11th

1.6c below the 61 to 90 average
2.1c below the 81 to 10 average

___________________________

Current high this month 8.6c on the 11th
Current low this month 6.6c on the 1st

[Roger J Smith]

EWP now around 52 mm, was at 47 to 11th, about 5 mm yesterday. 10-day maps showing 25-30 mm and day 11-16 maps about 20 mm, total by 29th would be at least 100 mm, possibly higher. Will be interesting to see if 60-70 mm model prediction for Devon in next 36 hours verifies, not a big factor in the EWP total as only 5% or so of the grid. My estimate for CET by 29th from the current GFS run is close to 10.5 C. Could still be pulled down by adjustments so anywhere in the 10s seems a good bet. 

[Relativistic]

I decided to look at means for the 40-day period 1st April to 10th May.

The provisional value for this year is 6.9C (a 0.3C downward correction for the first 10 days of May would just about see us round down to 6.8C). The last time the mean was this cold was in 1941 (6.5C), and during the 1900s there were only two further instances where the mean was colder: 1917 (6.6C) and 1922 (6.7C). Beyond that, we have 1887 (6.8C), 1879 (5.8C), 1837 (5.9C), 1812 (6.5C), 1809 (6.4C), 1799 (6.0C), and 1782 (5.4C). So provisionally we're 11th coldest on record for the period.

Edited May 12, 2021 by Relativistic

[summer blizzard]

I’m surprised that the GFS would not deliver higher but allowing for its continued retreat from pressure building it does look like the coldest since 96 is probably odds on now.