Precision warnings…

I know that the latest super computer and the new model had given the Met Office even greater resolution with their forecasts, but I never realised that it could be relied on to the degree of precision that they claim in the latest warning that they’ve just issued for east Lancashire for tomorrow morning (fig 1). I know than rainfall intensity increases with height, and that there’s a fair bit of high ground in this yellow warning area, but to be so confident to say that heavy won’t cause problems on the M6 motorway, but will further east in a relatively small area around Burnley, seems at best overly confident, and at worst a little reckless. We shall see what transpires, perhaps the accuracy out to T+30 with rainfall intensity is that precise these days.

Figure 1 – Courtesy of the Met Office

It’s interesting to see that the larger Bolton just NW of the larger Manchester population 128,139 is still being labeled on the warnings map, in preference to the smaller Bolton just outside Appleby in Cumbria, population 435.

A dry June in south Devon

I should have realised that the spring dry spell hadn’t completely come to an end by the large cracks that have returned to our Devon garden. The figures reveal that Exeter airport is the driest place in the British Isles so far in June 2017. As far as I can see I have a 100% reception of the 06 UTC 06-06 rainfall values, but I’m a little skeptical that the rain gauge hasn’t been blocked, but I’m sure the Met Office are on the case and will reveal all in the course of time.

Figure 1

There are some other places in the UK that have also been quite dry this month, especially across the east Midlands, with Bedford (17.8 mm) and Wittering (18.6 mm) notable amongst them (fig 1 & 2).

Figure 2

So the dry theme continues to reoccur across Devonshire in 2017, with just 271 mm of rain in the first six months at Exeter airport (fig 3), which for such a wet county is remarkably low. It’s got so bad that we went out bought a second water barrel for the pond and garden yesterday, because a single 210 litre butt just wasnt enough.

Figure 3

I posted a similar blog at the end of April about the drought conditions, on the last day of the month we had almost 2″ of rain in a day. The latest NWP forecasts paint the next week as wet and cyclonic at times, which will likely redress the balance in rainfall in this part of the world I’m sure.



The unusual warm and anticyclonic spring of 1893

Figure 1

I noticed that the warmest spring* in the daily CET record back to 1772 in Central England was 1893. I don’t make a habit of looking for exceptional warm springs in the Victorian era, it was just that the spring of 1893 was even warmer than the spring of 2017 which has just ended (fig 1). The other thing that caught my eye was how exceptionally high the mean maximum was (anomaly +3.82°C), and how comparatively normal the mean minimum (anomaly +0.37°). This obviously points to a very anticyclonic regime back in the spring of 1893 to produce very warm days and comparatively cold nights, the graph below (fig 2) shows the contrasting anomalies during that spring perfectly.

Figure 2

So just how anticyclonic was it? A quick scan of the reanalysis charts for that spring reveals it was very anticyclonic.

Figure 3 – Courtesy of Wetterzentrale

Here are the headlines from the monthly weather reports compiled by the Met Office back then:

  • March 1893 Exceedingly fine and dry in all but the extreme north and northwest where showers were more frequent.
  • April 1893 Remarkably fine, warm and dry, especially over southern England where the severe drought continued with scarcely any intermission.
  • May 1893 Mostly fine and dry, especially in the south and east till mid-month, then unsettled with rain and thunderstorms in places.
  • June 1893 Generally fine and dry first half with local thunderstorms, the second half saw frequent showers and thunderstorms.

As you can see from the LWT analysis (fig 4), spring 1893 is easily the most anticyclonic in the series that started in 1871, with 58% of LWT being either anticyclonic or anticyclonic hybrid. It wasn’t cold, because the predominant flow was generally southeasterly or southerly rather that east or northeasterly. Spring 2017 is currently in 22nd position with a couple more days of records to go.

Figure 4 – Data courtesy of the CRU/UEA

It was also the second driest spring [MAM] since 1766 in England and Wales (fig 5).

Figure 5 – Data courtesy of the Met Office

*  I’m old-fashioned, and because of this I prefer to use seasons that start and end (approximately) at the times of the various equinoxes and solstices, so most of these stats are based on so-called ‘astronomical’ rather than ‘meteorological’ seasons.

What triggers sudden dry spells?

Figure 1

It’s as if someone turned a tap off at the start of October last year in Northern Ireland. The graph above (fig 1), is a rolling 365 day moving accumulation, the yellow highlighted line is a 365 day moving average of that moving total (if that makes sense), to smooth out the accumulations. This sudden drop is mirrored in most, if not all regions, across the UK despite the rainfall in May, but is more marked in Northern Ireland. The steep decline in annual accumulations was brought about by a series of drier months from July 2016 onwards, that followed the previously wet Autumn and Winter (2015-16), but what triggers these sudden dry spells to suddenly stop and start is another question. The last one in Northern Ireland, occurred in 2004, it will be interesting to see just how quickly it bounces back. It happens the other way round of course, when a wet spell suddenly starts like it did at the end of 2015, but it never seemed as marked as when a dry spell starts.

Here’s another way of looking at the same daily values (fig 2), and as you can see, the accumulations deficit went negative at the start of last years anticyclonic October.

Figure 2

And here’s one that I prepared earlier for the Southeast of England, the deficit is still evident at the end of May, but has probably narrowed in the last week.

Figure 3


Ingraban continues to play havoc with flaming June

Figure 1

Large 24 hour rainfall totals have been recorded across the northeast of both England and Scotland in the last 24 hours ending 06 UTC, and it’s still raining in Northeast Scotland. There is the odd white pixels in my estimates from the weather radar south of Nairn, which indicate accumulations in excess of 150 mm (fig 1), so I expect that the rivers Spey, Findhorn and Nairn are all now in full spate after the deluge of the last 36 hours. Wettest from the observations was Loftus in North Yorkshire, with 58.2 mm in the 24 hours (fig 2), Edinburgh wasn’t far behind with 48.6 mm.

Figure 2

The inset observation grid are the last 24 hours observations from Lossiemouth, overlaid on a map of 24 hour rainfall totals (fig 3).

Figure 3

The heavy rain brought down the freezing level overnight as well, so the very tops of the Cairngorms could have seen some of this rain fall as snow, that combined with a 50 knot mean northwesterly might put a hold on your plans to knock of a few Munros in the area today (fig 4). The Met Office were too frit to call this storm Fleur, but the Berlin Meteorological Institute ended up naming this particular vortex Ingraban, either way this vortex continues to play havoc with flaming June.

Figure 4

I see the upper cloud from the next feature as got well into Ireland now (fig 5), and looking at the forecast from the GFS model, it looks like Thursday and Saturday will be wet again, in many areas, particularly the further northwest that you are in the country. After the weekend though, things look like they start to settle down, and next week we may well see the return of flaming June.

Figure 5

6 June 2017 – rainfall

Figure 1

It’s the turn of the east coast to take a soaking today, and pretty dreich it’s been down along east coast for much of the day. Wettest place in the list of available observations is Edinburgh with 35 mm in the 12 hours ending 18 UTC (fig 1), I overestimated the total their by around 15% (fig 2), and also managed to underestimate the Weybourne total in Norfolk by a similar margin. Plenty of places on the higher ground of Scotland, Cumbria the North York Moors with rainfall totals well in excess of 50 mm today, which is not bad going in 12 hours.


Figure 2

The northwest Highlands seem to have escaped the yellow warning for rain today, as did Gogar Bank with its 35 mm, because it lies outside the yellow alert area just to the west of the city. It looks like eastern Scotland will see a lot more before it’s done.

Figure 3 – Courtesy of the Met Office

Yesterdays rainfall totals

Figure 1

My estimates for Capel Curig were around 20% too high at 102.3 mm for the 24 hour period ending at 06 UTC this morning, the actual there was 82.6 mm, I put the difference down to my mapping, and the low resolution of the radar image on the Met Office website, which is fairly coarse and certainly not up to the 0.5 km resolution that you can find on Netweather, but beggars can’t be choosers.


Figure 2

What the accumulations do show quite dramatically is how the east Midlands and East Anglia escaped the worst of the heavier rain, all though they might not be so lucky today.

Monday, 5 June 2017 – rain

Figure 1

My estimate for Capel Curig since 06 UTC this morning is very close to 60 mm of rain so far (see inset hyetograph in fig 1). There are also scattered red pixels over Snowdonia, which means totals in excess of 75 mm, to a lesser extent, there have been totals of between 32 and 50 mm over the southern Cumbrian fells, south Wales and southern Dartmoor. Still some more rain to come in the west as the cold front come through during the evening and night.

Looking at the actual 06-18 UTC rainfall reported totals, I see that my estimate for Capel Curig was around 20% too high – well you can’t win ’em all (fig 2). The Plymouth estimate of 17.9 mm was closer, and the Trawsgoed estimate of 20.9 mm was closer still.

Figure 2

As regards this morning’s yellow warning of heavy rain, which runs through till 10 UTC tomorrow, the Chief forecaster said and I quote:

This has the potential to widely generate 40 to 60 mm of rain and as much as 80 mm over some areas of high ground, most likely in Cumbria and Snowdonia.

Well with over 16 hours to go, we’ve already seen those kind of values across those areas of the country.

Southwest left out of the yellow alert

Figure 1

It may not be long before an additional area is added to the yellow alert for heavy rain for the southwest of England if the rain keeps falling like it is at the moment (fig 1), even though the frontal clearance can’t be that far away and everything is moving quite swiftly. A truly horrendous time for anyone on holiday at the moment in these parts of the UK. The winds have been pretty lively this morning as well, here are the maximum gusts for the last 24 hours (fig 2).

More reminiscent of early Autumn than early summer

Quite a week of weather coming up for the British Isle in the next week, if these latest GFS forecast frames are anything to go by. Very mobile till the weekend, with a pulse of very warm air for Saturday and Sunday thrown in for good measure. The gradient over northeast Scotland looks very tight on Wednesday, and there’s plenty of more rain to come for western areas, both on Wednesday and Friday by the look of it.

Figure 1