Liscombe top of the shop

Figure 1

It’s not very often that you’ll see Liscombe in Somerset (and not in Devon as I had always thought) as the warmest place in the British Isles, but it happened today with a temperature of 15.0°C at 15 UTC (fig 1), in fact it was a southwest one two with Exeter Airport second in the table (fig 2), but I bet you won’t hear about that on the BBC weather.

Figure 2

You can’t even call Liscombe a village in all honesty, there is a Liscombe Farm, but the AWS is a little way to the east up what looks a very lonely lane on Exmoor at a height of 348 M (fig 3), so it might be getting a little help from the northwesterly wind.

Figure 3 – Liscombe courtesy of Google Maps

The 1⋅6% humidity at Altnaharra…

2016-12-03_154343

Figure 1 – Courtesy of the BBC

I came across this news story whilst reading a book called “Since records began” by Paul Simons. On researching the event on Google I found this news article about it on the BBC website (fig 1). There’s no doubt that the 18th of February 2003 was a mild day – the maximum reaching 11.5°C at Altnaharra making it was the warmest place in the UK. This was in no doubt due to a foehn effect in the strong southerly flow over the mountains to the south.

But it wasn’t the temperature that was the remarkable thing as Paul Simon’s mistakenly suggests in his book, but the relative humidity. In the 0952 UTC SYNOP observation from the automatic weather station [AWS] the dew point was an astonishing -39.9°C with a relative humidity of just 1.6%. The Met Office doubt that this was correct  and say that the relative humidity was closer to 8%. I’m not sure how they can be so certain about this, it maybe because they have access to one minute data from the AWS, but even so, a humidity as low as 8% must still rank as one of the lowest reported in the UK at a low-level station.

I love how Andy Yeatman sidesteps any embarrassment over this apparent mistake, I think in the news item almost trying to suggest that the wet bulb reservoir may have been frozen and the wet bulb had dried out, but if that was the case then the wet bulb temperature and hence the dewpoint, would have been much higher and not lower. Here’s the thermograph for that period (fig 2).

thermograph-for-altnaharra-1146-16-02-2003-1800-19-02-2003

Figure 2

And here are the hourly observations for Altnaharra for that day (fig 3). The winds do look a little strange and were flitting around a bit around 08 UTC.

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Figure 3

The 12 UTC chart (fig 4) is dotted with low dew point observations across Scotland that day, notice the -11°C at Cairnwell and the -13°C at Kinloss.

synops-1200-utc-on-tue-18-feb-2003

Figure 4

The Torrey Canyon and the Seven Stones reef

The Sevenstones Lightship (fig 4) is anchored 15 miles (24 km) to the west-northwest of Land’s End, and 7 miles (11 km) east-northeast of the Isles of Scilly (fig 1). According to Wikipedia, there has been a Lightship there since 1841, to warn vessels of the danger of the Seven Stones reef, which over the years has sunk 71 named ships, and possibly another 200 unnamed others. I would like to give you more details about the Seven Stones reef but it’s impossible to get a decent detailed bathymetric map for around the coast of the UK, it seems that although we may have ruled the waves for a long time, we now charge an awful lot for finding just out how deep the waters are around our sceptred Isle, perhaps the Ordnance Survey can take over the Hydrographic Office and free up some of this data, but I digress.

The Seven Stones reef is where the Torrey Canyon came to grief 50 years ago on the 14th of March 1967. The accident happened in daylight, when the ship was still to the southwest of the Lightship, but the reef is almost 15 miles long. The board of inquiry laid the blame on the Captain, who was apparently taking a shortcut to save time getting to Milford Haven (fig 2), maybe if their approach had been at night, he might have spotted the light and avoided the disaster, who knows.

Figure 2

Believe it or not this article started out being about the wave heights this Winter reported by the Sevenstones Lightship! I didn’t at first consciously connect the 50th anniversary of the Torrey Canyon disaster with the Sevenstones Lightship, so here’s what’s left of the original article that I’ve written.

Figure 3

The above chart is of hourly wave heights, as reported by the Sevenstones Lightship from the 1st of December 2016 through this last Winter (fig 3). On top of the hourly scatter graph I’ve overlaid four of this seasons five named storms. The highest reported wave height of 7.4 metres this Winter, occurred during the unnamed or Candlemas low of the 2nd of February. The other named storms align poorly with any of the peaks in the 24 hour moving average of wave heights that I’ve also plotted for Sevenstones though.

Figure 4 – The Sevenstones Lightship

The last week on Mount Washington

Figure 1 – Courtesy of Mount Washington Observatory

The last week’s weather has been quite eventful atop Mount Washington, in the (very) White Mountains of New Hampshire. The observatory reports every six hours and here are the plotted SYNOPs for the last week (fig 2). As the low that produced the nor’easter of the last 24 hours passed to the east, the winds at the observatory increased to mean 82 knots at midnight.

Figure 2

As you can see last week the freezing level was above the top of the mountain (6,288 feet) and there were rain showers in a force 10 southwesterly, and just three days later the air temperature had fallen to -38.0°C and the winds had increased to mean 65 knots and veered west northwesterly. There are a couple of things that puzzle me about their observations, and one of them is snow depth. Why do they even bother trying to report a representative snow depth? Last night for instance, the mean wind speed was 82 knots (94 mph) and was gusting to 128 knots (147 mph)? And yet between midnight and 06 UTC, they reported that the snow depth had increased from 20 to 21 cms (fig 3). There is no way on earth that could be level snow, and what snow that did stick would be on the lee side of the mountain or observatory and considerably drifted and corniced. By the way, I’m assuming that the local nine group they use in their observations (93128), is in fact a gust group that only seems to be added, when the gusts are 100 knots or higher. I know that the Americans, like the Australians, aren’t big fans of the SYNOP format, but why can’t they just use the WMO standard reporting group for reporting gusts?

Figure 3

In comparison and with typical German precision at the Zugspitze Observatory in the Alps they do things a little more by the WMO book (fig 4). They report hourly observations for a start, that includes gusts, a believable snow depth, it may well be that because the winds are lighter there that they can do this more easily. Snow depths increased in excess of 4 metres during the last week there. They also report rainfall (equivalents) and air pressure adjusted to the 700 hPa level, which Mount Washington don’t do in a four group, just a ‘as read’ pressure in a three group. One thing that the Americans do report, which I think should be adopted more widely, is six hourly max and min temperatures.

Figure 4

Make that 17°C in Devon

Temperature now 17°C in Bradninch at 1350 UTC a gloriously sunny spring afternoon which makes a change from the overcast weather of the last few weeks.

Figure 1

The AC layer has thinned, and it’s been sunny for most of the last hour.

Figure 2

As an ex-metman I don’t get round to doing many SYNOP observations of my own these day, so when the Exeter airport observation went missing (again) and the temperature here reached 60°F, I thought that I would make up a WMO designator (03838) for our village of Bradninch, and add one of my own SYNOP observations with a little help from my trusty Vantage Pro.

Gust to 119 mph at Ushant

Figure 1

I haven’t been keeping count, but there seems to have been no end to the number of vigorous lows running across France since the New Year, and today is no exception. The gust reported in the 12 UTC plotted observation (fig 1) from Ouessant-Stiff (WMO 07100) of 103 knots or 119 mph, actually occurred at 08 UTC (fig 2), and I must admit that I never realised just how fiery the latest low had been went it made landfall this morning.

Figure 2

 Here is a list of the highest gusts as reported in the 12 UTC SYNOPS (fig 3). I don’t know why, but we seem to call the French island of Ouessant – Ushant.

Figure 3

Figure 4 – Le phare du Stiff (courtesy of Wikipedia)

Kurt slips between St Mary’s and the Seven Stones Lightship

Low Kurt is now moving quickly north, and just before 11 UTC had slipped between the Scilly Isles and the Seven stones Lightship (fig 1).

Figure 1

Here’s a bit of a close up (fig 2), the highlighted station is St Mary’s, the observation to the northeast is the Seven Stones Lightship.

Figure 2

It’s been quite a couple of days at St Mary’s here are the last 24 hours plotted observations (fig 3). There’s a sharp drop in temperature behind the occlusion from 9.6 to 5.1°C I notice.

Figure 3

And here’s the Lightship at Seven Stones, although it looks almost circular in this image, I’m sure that it does have a bit of length about it.

Figure 4

A little bit wilder than in the image as you can see from the observation from the Lightship itself (fig 5).

Figure 5

Looking back at the Burn’s day storm

Figure 1

Better late than never I thought that I would look back at the Burn’s day storm that occurred on the 25th and 26th of January 1990 with the help of the NCEP reanalysis data. As well as SYNOP data, I can now overlay a 2.5° x 2.5° grid of MSLP reanalysis data to fill in any missing gaps in the coverage. Of course it would be better if this grid were a little finer, but beggars can’t be choosers, and it does so improve the contouring. One thing I would say is that although we may not have had the weather buoys that we have these days there were a lot more ship reports back then, probably due to greater efforts made after the October storm of 1987.

Figure 2

It’s also a chance to see some of the old stations, that sadly have now disappeared. In these days of AWS you would have thought that there would have been a renaissance in observing sites at places such as Lighthouses, but automating the light didn’t mean that Trinity House were going to automate the weather observations from them, which is a great shame, and a missed opportunity.

The Burn’s day storm was a much deadlier storm than the one of October 1987 and led to the death of 97 people in this country, and 30 more has it tracked across the low countries. The Wikipedia article about it says that this was due to the fact that it occurred in day time, which may be true, but the winds across the southwest look a lot more severe at least to me. The highest gusts in the storm was 93 knots (107 mph) from Gwennap Head and Aberporth, but although the highest gust on the 12 UTC chart was 90 knots (fig 3), it was the mean speeds that were the main feature of the Burn’s Day storm as far as I can see, with many stations across the southwest reporting storm force winds, Beaufort force 10 with mean speeds of 48 knots or higher.

Having said that all that about Lighthouses, Gwennap Head is not one of them (img 1), even though it sounds like it should be, but just a mere Coastguard look-out station, a little like the one at Berry Head, and lying just a few miles southeast of Lands End.

Image 1 – Courtesy of Wildlife Insight

Image 2 – Courtesy of Bing Maps and the Ordnance Survey

Wolf Rock is a lighthouse though (img 3), and lies around 14 km to the southwest of Gwennap head, and I wonder just how windy it got there on that Burn’s day? I imagine that the gusts probably weren’t just quite as strong as on the headland, even though the lighthouse (which was finished in 1869) stands 41 M tall (135 ft), I imagine that the westerly violent gale (Beaufort force 11) blowing up those 66 M (216 ft) high cliffs may have added an extra bit to those gusts. I bet you could hear the sound of a wolf from the rocks on that day though.

Image 3 – Courtesy of Wikipedia

Intense Ottawan high

Figure 1

There’s an intense high sat over Ottawa on the 06 UTC chart this morning of around 1044 hPa. You usually associate light winds with anticyclonic weather, but not this morning on Mount Washington just to the southeast of the centre in New Hampshire, the wind from the observatory was meaning 62 knots (77 mph) at 06 UTC, with an air temperature of -24.4°C, and a resultant wind chill of -47°C (-52.6°F (JAG)).

Figure 2

Mount Washington Observatory – Home of the world’s worst weather

Figure 1 – Copyright W.Woods

Mount Washington as you may well know is located in the Presidential Range of the White Mountains, in the state of New Hampshire in the United States.

Figure 2 – Courtesy of Bing Maps

Mount Washington (called Agiocochook by some Native American tribes) is the highest peak in the Northeastern United States at 6,288 ft (1,917 m). The mountain is notorious for its erratic weather and on the afternoon of April 12, 1934 a wind gust of 201 knots (231 mph) was recorded at the summit. This stood has the world record for highest wind speed for most of the 20th century, and is still a record for a wind in an extratropical cyclone. The Mount Washington Cog Railway ascends the western slope of the mountain, and the a road climbs to the summit from the east. The mountain is popular with hikers and the Appalachian Trail crosses the summit. Thanks to the Wikipedia article for that information.

Figure 3 – Courtesy of Google Maps

There’s been an observatory on the mountain since 1932,  and recently the SYNOP observation from WMO station 72613 have become more available than they have in the past, although they’re still only available for main synoptic hours. I did think of volunteering to do a stint as an observer at the observatory, but never quite managed to submit the application. Volunteering would have been akin to what Victorian meteorologists did back in November 1883 when they started to continuously man the observatory that they had built on top of Ben Nevis. Anyway here is the latest pseudo anemograph (fig 4) that I’ve put together from the last month’s climate data.

Figure 4

A constantly windy place, usually from the west during the last month, with a mean speed usually of force 8 or 9, with occasional periods of force 12 or more, the yellow outlined line in the top chart by the way is the 24 hour mean centred wind speed in knots. It’s a real shame that Mount Washington observatory don’t include a gust group in their SYNOP reports which I download from OGIMET. Of course it could be a very constant high wind speed in a laminar flow with few gusts, but that’s a totally illogical reason for it being omitted. Take a look at Cairngorms anemograph for the same period (fig 5), of course they are around 2,951 miles apart on opposite sides of the North Atlantic Ocean, and Mount Washington at 6,288 feet is 2,204 feet higher than Cairngorm, but it will give you an idea of the gustiness on top of Cairngorm in the last month. Cairngorm does punch well above its weight for its height, and at times the 24 hour mean wind speed was over 60 knots and higher than Mount Washington, this was in mid-December as Storm Barbara and Conor were passing to the north.

Figure 5

Here is a list of some of the raw SYNOPs from Mount Washington for the last month (fig 6). I’ve looked using the WMO manuals for anything resembling a supplementary group that reports the highest gust for a period, but did not find one – let me know if I’m missing something. The odd thing is that although they don’t report a maximum gust they do report a snow depth, which I find very odd given that the mountain is constantly being subjected to storm force and at times hurricane force winds. I would have thought the ground would have been scraped clean of snow, and that the only real snow would exist either in the lee of the observatory buildings or in giant cornices around the edges, which would make snow depth reporting impossible.

Figure 6

Mount Washington is certainly very much colder than Cairngorm is. This is mainly due to the fact that it’s a much higher mountain and even though it’s situated further south at 44° rather than the 57° of latitude Cairngorm is. The other reason it’s colder is that it’s situated on the eastern edge of the North American Continent, and the Pacific Ocean were the prevailing winds are coming from are a very long way indeed, Cairngorm in comparison is probably no more than 60 miles from a comparatively warm North Atlantic Ocean. The thermograph for Mount Washington (fig 7) shows just how exceedingly cold it can get, with Arctic air rushing directly down from Canada in the winter to produce some massive wind chill values, it’s certainly not a mountain to get lost in winter on, and that’s for sure. The other thing to notice in the SYNOPs (fig 6) is how frequently the visibility switches between either excellent (code 89=>70 km) or zero (code 00=<100 M).

Figure 7

If you search the Internet for images of Mount Washington, you may find like I did that they are all heavily copyrighted to protect them, maybe because the whole mountain is now owned by the Florida based CNL Financial Group, who are trying to file a trademark for the name “Mount Washington”. There are many amazing images of a snow, ice and rime covering Mount Washington (in fact if you like rime this is the place to see it), but because I can’t seem to use any of these images freely here’s a list of hyperlinks to some of the best and most interesting ones, you’ll notice that most of them come from the Mount Washington website or Facebook page.