April 1995 synoptics

[North-Easterly Blast]

With frequent talk that August 2006 should have been cooler than it actually was, I have another month in question when looking through the archives, April 1995.

When looking through the archived charts, April 1995 featured mostly high pressure sat over the UK during the first half, (very similar to the setup progged for this coming Easter Weekend in 2007), and even a brief Bartlett around the 2nd, with low pressure frequently passing through the GIN corridor. The second half featured a Greenland High from the 18th -22nd and northerlies covering the UK, and looking at the bigger picture these northerlies were from way up into the Arctic, and then lower pressure to the south of the UK turned the winds easterly for the final week of the month, and admittedly, these easterlies from the 24th-29th April 1995 were from central and northern Scandinavia, so certainly still a cold source even at this time of the year.

Despite the fact that there were true cold synoptics throughout the second half of April 1995, and even for much of the first half high pressure was rarely in a position where it could pull up extremely warm air from Africa, (such as in mid April 2003); the month still ended up being a full degree above average for the CET at 9.1*C. In my view the synoptics of April 1995 should at least have produced a CET close to average, and the synoptics of the second half should have given a much colder than average second half, but the month still managed a positive anomaly of 1*C, how did this come about looking through the synoptics? Plus more specifically, the 1988-1996 era was only in a Stage One modest warming for the UK compared to the Stage Two consistently warm period of the post 1997 era.

[Glacier Point]

1995 has some interesting parallels in terms of the teleconnections this year...

Both years fell at low points of the solar flux.

Both years followed rampantly +ve AO winters - both record breakers in this respect.

Both years featured upper level weaknesses around the Azores-Canaries-Iberia during the Spring (which continued into the Summer).

Both years featured a decaying Spring El Nino.

However, the SSTAs are not similar and this year I think we are looking at a strengthening La Nina which will differ from the ENSO neutral conditions experienced in 1995.

So, as a very broad analysis from these comparisons, I'd suggest a similar Summer but with an increasing influence of La Nina as we progress, particularly mid July onwards.

GP

[Nick F]

I think it was probably the case in April 1995 of the maxes and mins being pretty high in the first half of the month up until the 14th which pushed the CET above average despite the colder 2nd half. The first two days saw maxes of 20-21C quite widely over England, then 20C was reached again in a fair few places on the 6th, max temps were widely in the mid teens or above from 1-7th then 10-14th over England. After that it turned colder especially around 18-19th as a N'erly established, but temps recovered after the 20th with maxes of low-mid teens and mins in high single figures.

I also suspect an abundence of sunshine in the 2nd half of the month during and after the N'erly established meant that temps rised rapidly during the day after chilly nights with the strong sun in late April. If it were predominantly cloudy, with a cold air source, then it may well have had a greater affect on the CET.

[North-Easterly Blast]

Glacier Point; how is La Nina likely to influence our summer weather?

So, what wrecked winter 2006-07 for cold in the UK? My view was partly the very warm September and the prolonged mild SW'lies throughout the autumn that sent very mild air even as far north as northern Scandinavia and western Russia and prevented a build up of a cold pool there until much later in the winter, and the SST anomaly in the Pacific also wrecked winter 2006-07. A SST anomaly of an El Nino together with cold anomalies in the north Pacific just enhances the northern arm of the jet and is curtains for a cold winter in the UK.

I do not know what the correlation is between a La Nina and summer weather in the UK.

[Glacier Point]

Glacier Point; how is La Nina likely to influence our summer weather?

I've yet to do a full analysis, but intitial indications for La Nina alone would be a fine and warm June followed by a rapid decay to very unsettled monsoonal type conditions for July and August.

We must however balance this with the climatic trend and state of the polar Stratosphere which are equally if not not more important, particulalry to western Europe. Which brings me onto the Winter..

So, what wrecked winter 2006-07 for cold in the UK?

Very briefly:

• Climatic trend;
  
• propensity for a cold polar Stratosphere arising from the westerly phase QBO and solar minima;
  
• Stratosphering cooling just at the right time during November to super-charge the polar westerlies resulting in record +AO during December-January;
  
• El Nino signal in the Atlantic for low pressure was as expected, but displaced much further north due to the above factors resulting in strong SW'ly draw with SSTAs well above average in this sector - note there was precious little sub-tropical flow.
  

The NAO was notably less +ve throughout the Winter and this supports the view discussed a few months ago that by far and away the most important climatic index for the UK is the AO. Any signal from the oceanic state of the NAO (which I still believe was for a neutral-negative value) was swamped by the state of the AO.

You could argue that 1995 does indeed mirror this type of pattern very well so a conclusion that we might be working towards a similar start to the Summer has some merit to it. It all depends if and how strong the La Nina event becomes.

GP

Edited April 5, 2007 by Glacier Point

[Thundery wintry showers]

The first half of April 1995 featured mostly anticyclonic westerly/north-westerly flows. Although they may have featured winds predominantly from the west or north-west, they originated from a warm source, thus the first 11 days of April 1995 was particularly warm, except in northern Scotland. Sunshine was generally abundant except in northern Scotland where it was mostly cloudy. The warm airmass and westerly drift kept the overnight minima quite high also.

http://www.wetterzentrale.de/archive/ra/19...00119950402.gif

http://www.wetterzentrale.de/archive/ra/19...00219950402.gif

12-14 April saw a relaxation of the generally westerly flow, and a dry sunny few days was had by almost all parts, with a fine start to the Easter weekend, temperatures in the high teens on Good Friday, cooler nights being insufficient to offset the warm days:

http://www.wetterzentrale.de/archive/ra/19...00119950414.gif

http://www.wetterzentrale.de/archive/ra/19...00219950414.gif

After midmonth a dramatic switch-around occurred, with cooler cloudier weather persisting for the remainder of the Easter weekend, and then come Tuesday 18 April, a northerly flow was unleashed, which brought sunshine and wintry showers over the next four days. The 20th was a particularly dramatic day in Cleadon, with showers of large hail depositing an inch of hail cover at one point.

http://www.wetterzentrale.de/archive/ra/19...00119950419.gif

http://www.wetterzentrale.de/archive/ra/19...00219950419.gif

We did have an easterly flow from the 23rd to 27th, but during the early part of this period, the easterlies were picking up air from a warm pool that had developed to our east while we were getting northerlies:

http://www.wetterzentrale.de/archive/ra/19...00119950425.gif

http://www.wetterzentrale.de/archive/ra/19...00219950425.gif

It turned cooler towards the end of the month, but high pressure then drifted away to the east, enabling exceptionally warm southerlies to persist during the first week of May, followed by another dramatic switch-around with northerly winds and wintry showers.

So, in essence, that is how April 1995 ended up rather warm in spite of the wintry spell on the 18th-21st. Spring 2007 is certainly showing some parallels with 1995, but so far, the warm spells have been vastly more dominant, relative to the cold incursions, than was the case in 1995.

[Weather-history]

The figures I have is that the first half of April 1995 was the warmest since 1945.

The mean temperature for the first half of April 1995 in Manchester was about 10C and there wasn't a maximum below 10C until the 16th

Edited April 5, 2007 by Mr_Data

[summer blizzard]

Personally, i think that the four major teleconnections, which will swamp all others are:

MEI

PDO

QBO

AO

In my opinion, the ideal summer teleconnections, are the opposite of what we want for winter, what i would like to see this summer is...

La Nina

Positive PDO

Westerly QBO

Positive AO

At the moment, it looks like we will see a weak La Nina over the summer, giving a bias towards above average temperature, above average rainfall and below average pressure in my opinion.

At the moment, it looks like we will see a neutral to positive AO this summer, giving a bias towards avove average temperatures, below average rainfall and above average pressure.

At the moment, it looks like will see a moderate easterly QBO this summer, giving a bias towards below average temeratures, above average rainfall and below average pressure.

At the moment, it looks like we will see a neutral to positive PDO, favouring above average temperatures, below average rainfall and above average pressure.

Since i'm bored, if i was forced to make a forecast right now, it would be..

CET - 1C above average (0.5C margin of error)

Rainfall - Around average (25% margin of error)

Pressure - Around average (25% margin of error)

Based on my interpretation, i expect the most common airmasses to be tropical marintime and polar arctic (straight northerly), i expect three ten day spells of European blocking due to a very positive PNA coupled with a positive AO and two ten day spells with dominant mid-Atlantic blocking, i expect the other 4 ten day spells to feature more average weather.

Given what Glacier Point has said, expect June to feature the very warm european blocking, and August to feature the Arctic weather types, i will have a look through later at individual months.

[Summer of 95]

April 1995:

The first two weeks as I recall were very sunny, dry and warm by day though fairly cold at night. However it changed very dramatically at Easter weekend (15-17th): suddenly (and this happened more than once during spring 1995) the high retreated into the Atlantic, and a vigorous Northerly set up residence- daytime temps tumbled and we had snow showers during the day. The Tuesday and Wednesday especially I remember being very cold for late April with temps as low as -4 at night ond only up to about 5 in the day. That week after Easter there was air frost here every night from Monday to Friday; then on the Saturday 22nd mild Atlantic mush moved in (unusually ffor spring 1995) and it poured all day- that day had something like 80% of the month's rainfall here. The last few days were fairly mild and uneventful before we had the most bizarre May with temps up to 25C in the first week, followed by 3 weeks of astonishingly cold weather for May with frosts and even snow.

[Weather-history]

. had the most bizarre May with temps up to 25C in the first week, followed by 3 weeks of astonishingly cold weather for May with frosts and even snow.

I thinks that a bit OTT. The middle third of May was certainly chilly with snow and frost but the last third wasn't especially chilly and temperatures had recovered somewhat getting into the high teens and in places the 20s.

However the first three weeks of May 1996 was remarkably cold. The first half of May 1996 was colder than the first half of January 2007 and we were very close to having the coldest May on record, the last 3 or 4 days prevented it. You be surprised how close we came to having the coldest May on record in 1996.

[North-Easterly Blast]

So what does all this mean for next winter 2007-08? Are any of the factors that wrecked winter 2006-07 likely to wreck next winter as well? Will last November's stratospheric cooling event affect the weather through the rest of this year and into next winter?

[Gavin P]

LOL! It doesn't mean anything for winter 2008. Its only April.

[Summer of 95]

I thinks that a bit OTT. The middle third of May was certainly chilly with snow and frost but the last third wasn't especially chilly and temperatures had recovered somewhat getting into the high teens and in places the 20s.

However the first three weeks of May 1996 was remarkably cold. The first half of May 1996 was colder than the first half of January 2007 and we were very close to having the coldest May on record, the last 3 or 4 days prevented it. You be surprised how close we came to having the coldest May on record in 1996.

I remember May 1996 being very dull, with very low daytime maxima (8-12C typically) but less extreme minima than 1995 (no doubt due to the cloud), and no snow. Certainly the cold, dull weather of May 1996 persisted almost throughout the month and I remember it being talked about in the press at the time. I think it ended up the coldest since 1902? Has there been a month so far below average since? I'd be very surprised if there was-

Actually I remember some time ago a discussion about these two Mays; I seem to remember that the period about 10th May-10th June was actually very similar in 1995 and 1996 in terms of temperature- 1996 had its hot week in early June.

Edited April 5, 2007 by Summer of 95

[Thundery wintry showers]

May 1996 had a CET of 9.1, 2.1C below the 1961-90 average; the closest to such an anomaly that we have had is December 1996 (CET 2.9, -1.8 below 1961-90 average and -2.2 below 1971-2000 average). January 1997 (2.5) had almost as big an anomaly.

Since then, the largest negative anomaly was the CET of 3.6 (-1.1 on 1961-90, -1.5 on 1971-2000) in December 2001.

The period 10 May-10 June did indeed have a similar mean temperature in 1995 and 1996. If I remember rightly, the middle third of May was similarly cold in both years (though with 1996 having lower maxima and higher minima, as correctly pointed out above), the final third of May 1995 was rather warmer than that of 1996, but then the first third of June 1995 was rather colder than that of June 1996, and the anomalies cancelled each other out.

The main reason why May 1996 ended up 2C cooler was because the first third was also cold, as opposed to May 1995 which began with a week of heat and sunshine rivalling the record-breaking heat of early May 1990, followed by the dramatic change to cold wintry weather. I recall that although May 1996 was a dull month in most parts, there were exceptions; up here in the North East it was quite a sunny month with an excess of 10-15%, about the same as in May 1995.

[Weather-history]

If I remember rightly, the middle third of May was similarly cold in both years (though with 1996 having lower maxima and higher minima, as correctly pointed out above),

Actually its the other way round, surprisingly

CET minimum for period 11th-20th May

1995: 3.6

1996: 3.2

CET maximum for period 11th-20th May

1995: 11.7

1996: 12.2

Edited April 5, 2007 by Mr_Data

[Optimus Prime]

May 4th 1996;

Quite an incredible chart for early May. SUbstantial cold pooling to the North East of Greenland with -15c 850's close to Northern Iceland. Cold air blown in by a North Easterly across Britain.

10th May 1996;

Unusually cold pooling across England for the middle of a typical May. About -5c 850s. Strong North Easterly.

Very cold on the 17th again;

Warm at the end of the month though with southerly wind developing. But low pressure to the west pushed the heat into the continent and so it wasn't especially warm for the start of summer.

[Lettucing Gutted]

If we at least expect December 2007 to be cold we could do with this April to be below 8.0c since 2001's cold 3.6 December followed a cold 7.7C April 2001.

Edited April 6, 2007 by Craig Evans

[Weather-history]

If we at least expect December 2007 to be cold we could do with this April to be below 8.0c since 2001's cold 3.6 December followed a cold 7.7C April 2001.

I don't see the connection and its ironic that you mentioned this in this thread because April 1995 had a CET of 9.1 and December 1995 had a CET of 2.3

[Thundery wintry showers]

A curious set of statistics here:

In Cleadon, we had 27mm of precipitation for the month. Although the month as a whole was mild, there was a significant cold snap on the 18th-21st, during which more than half of the precipitation total fell. The most dramatic day was the 20th, when 9mm (a third of the month's total) fell. It is probable that at least half of the month's precipitation fell as hail or snow, which is unusual for a mild month.

The above describes what happened in March 2007... but checking over my old weather records, it appears that I could just as easily be describing April 1995, for curiously enough, all of the above stats were also true of that month.

[summer blizzard]

There may be some life left in this thread if it is moved to the historical section, could a moderator please do this.

[Weather-history]

Here's the forecast from the 17th April 1995

[Snowyowl9]

Snow fell from the 18th to the 20th in showers gave a slight covering at most.

The 22nd was the coldest day with rain/sleet and snow with NE-ly winds felt very cold,but not as cold as yesterday which was about 3c lower.

The min`s were much lower though down to -5 on the 19th and 21st here.

[Thundery wintry showers]

Watching that forecast makes me wish we were faced with a similar upcoming spell of weather- seeing the bright showery weather set to head south and knowing we were set for another three days of it, with chances of hail and thunder as well as snow. I have vivid memories from Cleadon, with heavy snow showers on the morning of the 18th (albeit no accumulations) and also frequent hail showers on the 20th including one which gave an inch of lying hail. As per usual with showers it was quite hit and miss though- Manchester Airport appeared to be heavily affected with thunder on 2 days and sleet/snow on 3, but scattered locations in the south didn't see any wintry precipitation.

In fairness there is a chance of a similarly potent convective regime setting in after Easter this year, though with temperatures a few degrees up on the 18th-21st April 1995.

[Weather-history]

. As per usual with showers it was quite hit and miss though- Manchester Airport appeared to be heavily affected with thunder on 2 days and sleet/snow on 3,

Don't live too far away from the airport and I remember very few showers. There was an area of snow showers moving through in the first part of Tuesday morning then it was dry for the bulk of the day until evening when we had a snow shower. Wednesday was largely dry and the Thursday we had a few shoers in the morning.

[Weather-history]

The 19th April 1995 forecast

Edited April 7, 2012 by Mr_Data