April 2018 C.E.T. forecasts and optional EWP contest

[BornFromTheVoid]

Here's the forecast based on the 06z GFS

Rolling CET... Anomaly to 81-10 rolling avg (Daily Avg: Anomaly to 81-10 daily avg)

7.8C to the 9th.... +0.3  (8.2: +0.7)
8.1C to the 10th... +0.5  (10.7: +2.5)
8.3C to the 11th... +0.7  (10.1: +2.1)
8.4C to the 12th... +0.7  (9.3: +1.5)
8.6C to the 13th... +1.0  (11.2: +3.7)
8.8C to the 14th... +1.1  (11.2: +3.2)
9.0C to the 15th... +1.3  (12.4: +4.1)
9.2C to the 16th... +1.4  (12.0: +3.5)
9.4C to the 17th... +1.6  (12.3: +3.9)
9.5C to the 18th... +1.7  (11.9: +3.8)

Quite a bit cooler than the 00z early on, milder towards the end. Very mild, but no records under threat yet.
Starting to look like anyone that went for below average could have a bad month...

[cheeky_monkey]

sunny Edmonton is at -13.9c which is mammoth 18.9c below normal..might finally get above Freezing at the end of the week.

[The PIT]

Sunny Sheffield just outside the CET zone sat at 6.4C  -0.4C below normal Rainfall unchanged

[NorthYorksWeather]

7.6c here to the 8th, 0.8c above the 1981-2010 average.

Edited April 9, 2018 by vizzy2004

[damianslaw]

Yes a warmer than average month given model synoptics currently looking quite likely even at this early stage, especially given the fact that April is one of the months that tends to see a rapid warming in the rolling average from start to finish. We do have quite cool SST values around our shores though and the continent isn't warming up quite as much as recent years, so perhaps temps not yielding the potential high values they could do under similar synoptics in other years, but a finish at least 1 degree, possibly 2 degrees above the 61-90 average value quite plausible.. but as ever we could see a northerly plunge second half of the month as well - such is April, the most fickle month of the year when southerlies can become northerlies and we can go from winter cold to summer warmth in a flick of a switch. So always best to hold reserve until later in the month.

[Man With Beard]

A very good summary of where we are by @damianslaw above. 

IMO there is, though, a growing possibility of a 10C plus CET month, going by some of the latest ensemble output. Would be quite a shock given that the models were still toying with Beast Mark 3 just before April started!

[Summer Sun]

7.8 to the 9th

1.3 above the 61 to 90 average

0.3 above the 81 to 10 average

______________________________________

Current high this month 7.8 to the 8th & 9th

[BornFromTheVoid]

Here's the forecast based on the 06z GFS

Rolling CET... Anomaly to 81-10 rolling avg (Daily Avg: Anomaly to 81-10 daily avg)

8.0C to the 10th... +0.4 (9.9: +1.7)
8.2C to the 11th... +0.5 (9.7: +1.7)
8.3C to the 12th... +0.6 (9.3: +1.5)
8.4C to the 13th... +0.8 (9.9: +2.4)
8.6C to the 14th... +0.9 (10.9: +2.9)
8.8C to the 15th... +1.1 (11.5: +3.2)
9.0C to the 16th... +1.2 (12.0: +3.5)
9.3C to the 17th... +1.5 (14.9: +6.5) [Daily Record = 14.9C from 1865]
9.7C to the 18th... +1.9 (16.7: +8.6) [Daily Record = 14.5C from 1945]
10.2C to the 19th... +2.3 (18.0: +9.9) [Daily Record = 15.4C from 1870]

I normally do these updates every second day, but warmth at the end of the 06z GFS is just silly, so I had to post! That value from the 19th would be the second warmest April day on record. Something, certainly, to keep an eye on!

[The PIT]

Sunny Sheffield up to 6.5C -0.4C below normal. A drop tomorrow as today was a cold day. Rainfall 56mm 88.6% of normal.

[Summer Sun]

7.8 to the 10th

1.2 above the 61 to 90 average

0.2 above the 81 to 10 average

______________________________________

Current high this month 7.8 to the 8th, 9th & 10th

[The PIT]

Sunny Sheffield down to 6.4C -0.5 below normal. Rainfall 63.9mm 101.1% of average. Possible fall tomorrow as today was very cold.

[BornFromTheVoid]

Today's 12z goes a bit mad again, producing the 3rd and 2nd warmest April days on record on the 19th and 20th respectively. The anomaly for the 20th being over +10C!
Still a long way off, but the warming trend is there from today, with a notable acceleration from the start of next week.

[Don]

5 minutes ago, BornFromTheVoid said:

Today's 12z goes a bit mad again, producing the 3rd and 2nd warmest April days on record on the 19th and 20th respectively. The anomaly for the 20th being over +10C!
Still a long way off, but the warming trend is there from today, with a notable acceleration from the start of next week.

Looks like our nice little run of below average months has come to an abrupt end!

[The PIT]

Sunny Sheffield down to 6.3C -0.7C below normal so we're going to be well below normal by the end of the week which I wasn't expecting. Rainfall 65.5mm 103.6% of average

[Summer Sun]

7.8 to the 11th

1.2 above the 61 to 90 average

0.2 above the 81 to 10 average

______________________________________

Current high this month 7.8 to the 8th, 9th, 10th & 11th

[BornFromTheVoid]

Here's the forecast based on the 06z GFS

Rolling CET... Anomaly to 81-10 rolling avg (Daily Avg: Anomaly to 81-10 daily avg)

7.9C to the 12th... +0.2 (7.7: -0.1)
8.0C to the 13th... +0.4 (9.7: +2.2)
8.2C to the 14th... +0.6 (10.9: +2.9)
8.4C to the 15th... +0.7 (10.5: +2.2)
8.5C to the 16th... +0.7 (10.2: +1.7)
8.8C to the 17th... +1.0 (13.5: +5.1)
9.2C to the 18th... +1.4 (15.6: +7.5) [Daily Record = 14.5C from 1945]
9.5C to the 19th... +1.7 (16.6: +8.5) [Daily Record = 15.4C from 1870]
9.9C to the 20th... +2.1 (17.4: +9.0) [Daily Record = 16.6C from 1893]
10.3C to the 21st... +2.4 (17.7: +8.5) [Daily Record = 16.1C from 1893]

A big warm up now looking very likely next week, along with a string of potentially record breaking days.
Should the warm spell come off, then there sare some other records worth keeping an eye on:
Warmest April daily minimum of 12.4C from 2007.
Warmest April week of 15.1C from the 24th to the 30th 1775 (which includes the daily record of 19.7C on the 29th)
Most days averaging above 15C (4, from 2007)

[reef]

What is it with April these days? 10.3C by the 21st would put us within 0.3C of the 1865 10.6C record which stood for 142 years but was then broken in 2007 and again in 2011. This despite a rather cool start.

All months either side (January, February, March, May and June) have records that haven't been broken in 102, 239, 61, 185 and 172 years.

Its quite strange we keep getting these record (or near to) Aprils when no other month in the first half of the year has managed it. All six of the months in the second half of the year have broken records since 1994 though.

There's been a definite trend for more potent warm spells locally too. From 1980-2001, just five Aprils reached 20C here, yet 9 of the next 16 Aprils managed it.

[summer blizzard]

14 minutes ago, reef said:

What is it with April these days? 10.3C by the 21st would put us within 0.3C of the 1865 10.6C record which stood for 142 years but was then broken in 2007 and again in 2011. This despite a rather cool start.

All months either side (January, February, March, May and June) have records that haven't been broken in 102, 239, 61, 185 and 172 years.

Its quite strange we keep getting these record (or near to) Aprils when no other month in the first half of the year has managed it. All six of the months in the second half of the year have broken records since 1994 though.

There's been a definite trend for more potent warm spells locally too. From 1980-2001, just five Aprils reached 20C here, yet 9 of the next 16 Aprils managed it.

Not always abnormal to see. Oct 05 (i think it was 05 rather than 06) saw a cool first week. 

May 08 was running at near record pace at the halfway mark. 

But yeah, the potency of this spell (maxima not just breaching 20C but perhaps 25C) is abnormal.

[Weather-history]

1 hour ago, reef said:

What is it with April these days? 10.3C by the 21st would put us within 0.3C of the 1865 10.6C record which stood for 142 years but was then broken in 2007 and again in 2011. This despite a rather cool start.

All months either side (January, February, March, May and June) have records that haven't been broken in 102, 239, 61, 185 and 172 years.

Its quite strange we keep getting these record (or near to) Aprils when no other month in the first half of the year has managed it. All six of the months in the second half of the year have broken records since 1994 though.

There's been a definite trend for more potent warm spells locally too. From 1980-2001, just five Aprils reached 20C here, yet 9 of the next 16 Aprils managed it.

It is very stark that we've not had even a decently cold April for many years. Compare to the 1961-90 averages, April is the month that has the smallest -ve anomaly for the coldest of that month since the 1961-90 averages come into existence

January: -2.4 (2010)

February: -2.3 (1991)

March: -3.0 (2013)

April: -0.7 (2012)

May: -2.1 (1996)

June: -2.0 (1991)

July: -0.9 (1993, 2007, 2011)

August: -1.2 (1993)

September: -1.2 (1993)

October: -2.8 (1992)

November: -1.9 (1993)

December: -5.3 (2010)

 

[Roger J Smith]

Here is a complete list of years when April warmed by five degrees relative to March. This year will join the list if it makes 9.9 or higher since March was 4.9 C. To beat the record it would have to be warmest April by almost one degree (12.6). To finish third at 6.9 it would need to tie the record of 11.8 (2011). Interesting to find our doppelganger of 1785 at second place in the table (similar cold records in March although it stayed cold all the time in 1785). 

 

YEAR ___ MARCH __ APRIL ___ Increase 

1865 _____ 2.9 _____10.6_______ 7.7

1785 _____ 1.2 ______8.4 ______  7.2

1783 _____ 3.3 _____10.1_______ 6.8 

1814 _____ 2.9 _____ 9.6 _______ 6.7

1845 _____ 2.0 _____ 8.6 _______ 6.6

1674 _____ 1.0 _____ 7.5 _______ 6.5

1762 _____ 3.7 _____10.0_______ 6.3

1869 _____ 3.8 _____10.1_______ 6.3

1867 _____ 3.1 _____ 9.3 _______ 6.2

1883 _____ 1.9 _____ 8.1 _______ 6.2

1987 _____ 4.1 _____10.3_______ 6.2

1755 _____ 3.9 _____10.0_______ 6.1

1955 _____ 3.2 _____ 9.3 _______ 6.1

1709 _____ 3.0 _____ 9.0 _______ 6.0

1786 _____ 2.1 _____ 8.1 _______ 6.0

1796 _____ 4.2 _____10.2_______ 6.0

1840 _____ 3.8 _____ 9.7 _______ 5.9

1788 _____ 3.6 _____ 9.4 _______ 5.8

1747 _____ 2.5 _____ 8.1 _______ 5.6

1937 _____ 3.6 _____ 9.2 _______ 5.6

1789 _____ 2.1 _____ 7.4 _______ 5.3

1798 _____ 5.1 _____10.4_______ 5.3

1800 _____ 4.0 _____ 9.3 _______ 5.3

1844 _____ 4.7 _____ 9.8 _______ 5.1

2011 _____ 6.7 _____11.8_______ 5.1

1667 _____ 2.0 _____ 7.0 _______ 5.0

1909 _____ 3.7 _____ 8.7 _______ 5.0

1944 _____ 5.2 _____10.2_______ 5.0

1947 _____ 3.6 _____ 8.6 _______ 5.0

_________________________________________

A total of 29 years made this list. That is about 8% of the total sample of 359 years. 

The frequency has not dropped since 1900 but the intensity seems to be lower, the first case we encounter in the list after 1900 is T-9th 1987.

There were a rash of these large increases in the period 1783 to 1800 when eight years made the list out of eighteen. Another cluster was 1865 to 1869 when all three odd-numbered years made the list. The 2011 case is the only one with a March above 5.2 C (1944). In case you think I missed 2013, nope, 4.8 was the increase.

 

[Relativistic]

4 hours ago, reef said:

What is it with April these days? 10.3C by the 21st would put us within 0.3C of the 1865 10.6C record which stood for 142 years but was then broken in 2007 and again in 2011. This despite a rather cool start.

All months either side (January, February, March, May and June) have records that haven't been broken in 102, 239, 61, 185 and 172 years.

Its quite strange we keep getting these record (or near to) Aprils when no other month in the first half of the year has managed it. All six of the months in the second half of the year have broken records since 1994 though.

There's been a definite trend for more potent warm spells locally too. From 1980-2001, just five Aprils reached 20C here, yet 9 of the next 16 Aprils managed it.

The start of April wasn't particularly cool; only the 1st, 2nd, and 5th were below the 1981-2010 average.

I had a look at the Aprils that were 10.0C or more to the 21st, there being 11 in total. There are the following:

1945, 2011 (11.5C);
1943, 1865 (10.6C);
2007, 1949 (10.4C);
1783, 1803 (10.2C);
1814 (10.1C);
1946, 1798 (10.0C).

(Where months are equal, they are listed in descending order in terms of their values to two decimal places, e.g. 1945 was hotter than 2011 to the second decimal place. The only exceptions are 1783 and 1803, which were exactly equal to the 21st.)

Quite a few months prior to 2007 managed it. It's particularly interesting how there are two apparent clusters: if 2018 makes the list, that'll be three such Aprils in 12 years; we also had four such Aprils in just seven years back in the 1940s (this isn't the first time I've noticed frequent, exceptional Spring warmth in the 1940s).

The year you mention, 1865, didn't change overall from the 21st to month's end. Also of interest is April 1814, which saw a rare warm period in what was an extremely cold year overall (ranked 7th coldest on record (7.78C)).

 

Edited April 12, 2018 by Relativistic

[damianslaw]

I'm always a little unnerved when we see significant warmth in April, recent years such as 2007 and 2011 have been followed by poor summers.. I feel much less nerved for summer prospects when significant warmth occurs in May.

I think the effects of the SSW are still being felt and it is this which is giving rise to next weeks potential warm spell, we've got significant amplification in the flow, an elongated jet, something we have had since the SSW.

The warmth in April 2007 and 2011 was sustained though - and I don't expect it to be the case this year.

April sees the atlantic in its slumber and therefore has the greatest potential to deviate from average norms, the atlantic can be trapped for a long period, and if we see southerly airflows then significant warmth can quickly embed itself. Its always the month that catches everyone out! The least predictable of all.

[Summer Sun]

7.8 to the 12th

1.0 above the 61 to 90 average

0.2 above the 81 to 10 average

______________________________________

Current high this month 7.8 to the 8th, 9th, 10th, 11th & 12th

[BornFromTheVoid]

Warmth downgraded on the 06z, with the CET not reaching 10C within the his res time frame. Still a few record breaking days, but not quite the abnormal warmth shown in many recent runs.

[summer blizzard]

Of Mike's list if we take those since 1900 (all in the past 109 years) there are 7 years with 21 summer months. 

7 of those summer months were 1C or more below average (1909 looks truly horrific)

4 of those summer months were 1C or more above the average (but they came from 2 summers, 1955 and 1947)

Only 10 summer months (a minority) were near average.