Snow!

I saw some light snow, almost frozen drizzle, falling last night, but we woke to about 2cm on the ground, on branches and hedges. This was enough to make the world white, but the centre of the road was clear and where people walked, their footprints went right through to the pavement underneath.

As so often, this was from slightly warmer air pushing in from the Atlantic, into the very cold arctic air which was been feeding in from the North. It will slowly become less cold as the Atlantic air takes over, so more snow is unlikely unless the colder air returns.

Weather 2016

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In a nutshell, 2015 temperatures were 1.1C above the long term average with December 6.4C above. The Met Office say that it was the warmest and wettest December on record. September was significantly cool.

Rainfall was 5.6mm above the long term average. January and August were wet, while March, April and October were dry.

November Weather 2015

This November has been remarkably mild in Horley, apart from a brief, but significant cold snap.

Through almost all of the month, the jet stream flowed west-east driving a sequence of depressions off the Atlantic, bringing mild temperatures with regular rain and some windy times as fronts came through. there were a couple of genuinely windy spells with a force 7 (near gale) on 21, the strongest sustained wind recorded here in the last two years. This was a northerly, combined with low temperatures, so it felt particularly bitter. There were a nine days with gusts over 30knots.

Total rainfall was 82.8mm, with some rain falling on 24 days, and significant rain on 12. There were no days with more than 20mm rain. The total rainfall was 7.5mm less than the long-term average.

The mean temperature for the month was 10.5C, no less than 3.3C above the long-term average. The maximum for the month was 16.7C on 6th, but the daily maximum was above 15C from 2nd–17th inclusive. Despite a predominantly mild picture, there was an outbreak of air from the arctic from 21st to 23rd, which saw frost each night, mean temperatures below 3C and a minimum of -4.4C on 22nd.

                                      Heat  Cool   Avg
    Mean                              Deg   Deg         Wind      
Day Temp  High   Time   Low    Time   Days  Days  Rain  Speed High
------------------------------------------------------------------
 1   8.6  11.7   14:12   5.6   02:37   9.7   0.0   0.4   0.0   3.4
 2  10.6  16.1   14:37   8.6   06:38   7.7   0.0   0.2   0.2   8.6
 3  11.1  13.7   15:29   9.2   21:50   7.2   0.0   0.2   0.0   7.0
 4  12.2  13.9   14:00   9.2   00:03   6.1   0.0   5.0   0.1  10.4
 5  14.2  15.2   11:15  13.4   00:00   4.1   0.0  15.2   3.1  29.6
 6  14.9  16.7   13:38  13.3   05:50   3.4   0.0   5.0   3.2  26.0
 7  14.6  16.5   10:17   9.3   23:57   3.7   0.0   9.6   4.6  36.6
 8  12.4  15.9   18:17   7.1   03:51   5.9   0.0   0.2   3.2  26.0
 9  12.8  15.0   12:42   8.8   06:08   5.5   0.0   0.0   4.2  33.0
10  14.2  15.3   11:39  13.3   22:16   4.1   0.0   0.0   3.9  22.6
11  13.7  15.4   12:33  12.4   23:50   4.6   0.0   0.0   2.3  19.2
12  13.5  15.5   12:37  11.6   07:02   4.8   0.0   0.2   3.4  38.2
13   9.7  13.9   00:06   6.6   18:58   8.6   0.0   1.4   3.1  27.8
14  10.3  14.3   23:32   7.3   01:03   8.0   0.0  10.0   3.4  29.6
15  14.2  15.6   13:28  13.1   23:24   4.1   0.0   0.0   5.6  24.4
16  12.9  14.0   12:07  11.7   19:18   5.4   0.0   5.6   3.6  36.6
17  13.9  15.3   15:14  12.6   00:00   4.4   0.0   5.8   6.4  36.6
18  12.8  14.9   12:25  10.3   06:31   5.5   0.0   2.6   5.7  31.4
19  11.1  12.8   00:00   9.2   22:23   7.2   0.0   1.4   2.1  26.0
20   7.5   9.3   00:00   4.2   20:02  10.8   0.0   0.0   1.0  26.0
21   2.9   5.9   12:57  -2.2   23:45  15.4   0.0   2.8  12.0  45.2
22   1.0   6.4   13:31  -4.4   06:57  17.3   0.0   0.0   0.9  14.0
23   3.2   7.5   13:47  -2.2   07:04  15.1   0.0   0.6   0.1   8.6
24   8.0  10.3   08:39   5.8   20:46  10.3   0.0   8.8   2.2  19.2
25   7.6  10.3   13:14   4.4   23:55  10.7   0.0   0.2   1.7  24.4
26   8.1  10.2   13:19   4.1   01:27  10.2   0.0   1.6   0.1  12.2
27  10.2  12.2   11:10   5.4   23:58   8.1   0.0   2.6   3.9  33.0
28   6.5  10.4   21:23   1.6   07:51  11.8   0.0   0.2   3.0  27.8
29  11.4  13.2   15:37   9.5   00:13   6.9   0.0   1.0   6.1  34.8
30  11.6  13.3   21:22   9.1   04:45   6.7   0.0   2.2   4.3  26.0
------------------------------------------------------------------
    10.5  16.7     6    -4.4    22   233.3   0.0  82.8   3.5  45.2

Max >=  27.0:  0
Max <=   0.0:  0
Min <=   0.0:  3
Min <= -18.0: 0 Max Rain: 15.2 on day 5 
Days of Rain: 24 >= 0.2 mm  12 (>= 2.0 mm)  0 (>= 20.0 mm)
Heat Base: 18.3  Cool Base: 18.3  Method: Integration

Ex-Hurricane Kate

Early this week attention focused on the first storm named by the Met Office and Met Eirann. “Abigail” was a typical winter Atlantic storm, one of many which would be expected to impact on the British Isles each year. The reason for naming storms is explained:

As the UK and Ireland’s National Met Services, the Met Office and Met Éireann operate to maintain public safety through severe weather warnings and forecasts. Working together, it is hoped that naming storms will help raise awareness of severe weather and ensure greater safety of the public. The Met Office and Met Éireann will continue to issue weather warnings in the normal way using the Met Office National Severe Weather Warning Service and Met Éireann Weather Warnings. A storm will then be named when it is deemed to have the potential to cause substantial impacts in the UK and/or Ireland. To avoid any confusion over naming, if a storm is the remnants of a tropical storm or hurricane that has moved across the Atlantic, the already established method of referring to it as, e.g. ‘Ex-hurricane X’ will continue.

Abigail brought strong winds and some disruption to Scotland and parts of Ireland, along with heavy rain. Here, in southern England, it was nothing unusual for November: breezy and wet.

ex-Hurricane KateRight now, Weather across the British Isles is coming from a large, complex system of low pressure, another Atlantic storm, but this one has the remains of a Hurricane mixed up in it. Kate formed at the beginning of the month off the Bahamas and reached Hurricane strength just before it became part of an Atlantic storm system that had already left the north American continent heading westwards. This happens several times a year and the main effect is to add a great deal of energy and moisture to the storm as the hurricane adds enormous amounts of tropical air to what is already a clash between air from the polar region and air from the tropics.

This system has brought huge amounts of rain to the north and West of the country, especially Wales. This rain has been heaviest where the air has been forced up by terrain (“orographic” rainfall) and has been heavy enough to cause significant flooding. Again, here in the south of England, things have not been too unusual. We had light but very persistent rain for many hours yesterday, giving a total of about 10mm. It is also rather mild for the time of year as we experience a warm, wet tropical airmass. Today it is breezy, but nothing extreme.

As the system rolls through into Europe, it looks as if cooler polar air will be pulled down across the British Isles behind it, with temperatures likely to fall to seasonal norms, for the first time this autumn. November so far has been about 5C above the long term average for this location.

Chi Cygnids

A new meteor shower has been (provisionally) recognised and my meteor camera is playing a small part. Firstly, meteor observers around the world received a request that we should carefully check our data following a report of an “outburst”. This is not as spectacular as it sounds, simply that observers had noticed a number of meteors from the same part of the sky – too many to occur by chance.

P. Jenniskens, SETI Institute, reports the detection of an outburst from
a new Jupiter-family comet shower, the chi Cygnids (given IAU number 757 and
abbreviation CCY). Martin Breukers and Carl Johannink first noticed five
nearly identical orbits in multi-station video observations of the CAMS
BeNeLux network in the observing interval Sept. 14d19h23m-15d03h35m UT.
Partial results from the CAMS California network add four meteors in the
observing interval Sept. 15d03h10m-15d12h45m. The nine meteors detected
appeared between Sept. 14d21h and 15d11h UT (solar longitude 171.54-172.08
deg). The geocentric radiant is at R.A. = 301.0 +/- 2.2 deg, Decl. =
+32.6 +/- 1.6 deg (equinox 2000.0), with velocity v_g = 15.1 +/- 0.9 km/s.
The median orbital elements are (N = 9): q = 0.949 +/- 0.003 AU, a = 2.75
+/- 0.40 AU, e = 0.655 +/- 0.041, i = 18.6 +/- 1.6 deg, Peri. = 209.9 +/-
1.9 deg, Node = 171.64 +/- 0.23 deg (equinox 2000.0).


Confirmation of the outburst was found in the near-real time CMOR radar
observations (P. Brown et al., University of Western Ontario), which are
posted at website URL http://fireballs.ndc.nasa.gov/cmor-radiants/. The
24-hr averaged maps showed a small concentration of radiants at this
position during the observing period 15d05h15m-15d20h15m UT.

We were asked to analyse and send in video observations from around 15 September. I had already sent mine. Jakub Koukal (from the Czech Republic, who co-ordinates EDMOND the European database of meteor observations) then sent an email to Richard, another member of UKMON:

 … now i have one orbit of 757CCY (20150914_202235) between your east camera (Wilcot E) and Horley SE. After collecting all data, it will be time for recalculating elements. I found overall 51 orbits in EDMOND database from year 2007, with another outburst in 2010. This means that this shower is annual, with low activity between returns of potential parent body (comet from Jupiter´s family), and with outburst during perihelion passage of potential parent body (~5 years) – something like Draconids or Leonids. In attachment is confirmation (provisional) of this shower, based on current data, which i have.

757CCY

It looks as if the Chi Cygnids is a small meteor shower which peaks every five years to coincide with the return of an (as yet unidentified) comet which leaves debris in its orbit. If this is eventually confirmed, one meteor observation from my camera will be among a hundred or so which were used to identify the shower.

New meteor showers are being recognised all the time, partly as a result of good data from observations made with simple video equipment. It is a minor discovery. It will not change the world, but in a tiny way, has changed our understanding of it. I am pleased to have been part of real science, with lots of other amateurs and a few professionals co-operating around the world. That’s quite a good feeling!

Perseid Meteor and Space Station

 

I stepped outside to watch the International Space Station pass over. I love to watch it. Its stately movement across the sky is beautiful, and thinking about what it means is important, I think. As it moved away eastwards I saw the sudden flash of a bright perseid meteor below it. This was a classic perseid. Blue colour and with a little explosion at the end. All over in a moment, but lovely.

I was pleased to find that my meteor camera had caught it, so I could make a video to share at least a little of the experience.

Unusually slow meteor

The meteor camera I operate caught an unusually slow and long-lasting meteor at 00:18 on 1 August 2015. You can see what the camera saw in the video. Although the camera is noisy and grainy (it is  cheap, basic, but sensitive CCTV camera) it gives a great sense of the meteor sweeping right across the sky (actually about 60 degrees).

The meteor was also captured by several cameras in the UK Meteor Network and at least one in Nemetode, so the orbit can be calculated. It looks as if the meteoroid (the object in space before it hits the earth’s atmosphere and becomes a meteor) orbited between the orbits of Mars and the Earth. It was probably small, like a sand grain. It would have been completely burnt up in the heat of entry to earth’s atmosphere. It was travelling at about 6km per second or 21,600 kph (roughly 13,400 mph) so would have heated up very quickly as it hit the upper atmosphere.

It also looked beautiful through the clouds: a classic “shooting star”. The video is in real time. The meteor was roughly magnitude 0.7: similar to one of the bright stars but not the brightest thing in the sky and much less bright than many meteors.

Solstice

The Sun has reached its highest point in the sky, marking the beginning of astronomical summer and the longest day of the year. Solstice means “standing still” – a day when the path of the Sun across the sky does not appear to be moving up or down.

From now until 21 December, the Sun’s path will appear to move closer to the horizon and days will become shorter. This will happen in small amounts (a few minutes) especially at first, but the nights are already drawing in.

The atmosphere and oceans take time to warm up, so this is not usually the warmest part of the year, which is still to come.

White Nights

We are coming into the season of “white nights” around the summer solstice, when there is no true darkness because the sun is close below the horizon still illuminating the atmosphere even though the sun itself is not visible. In effect, the sun has started rising as soon as it has finished setting. Of course, if you were to travel further north, this phenomenon is clearer and more dramatic until, at the arctic circle, there are times when the sun does not set at all. We are at 51 degrees North here and the Arctic Circle is roughly 66.5 degrees North so we are about 930 miles (1,722km) short of the midnight sun, which is not that far compared with the size of the Earth.

There are degrees of darkness. We tend to call darkness that is not complete “twilight”. Civil twilight is when the sun is 6 degrees (or a little more than the width of a hand held at arms length) below the horizon. The horizon is clearly visible as are objects (such as mountains) even though, on a very clear night, the brightest stars are becoming apparent. Nautical Twilight is when the sun is 12 degrees below the horizon. The horizon is no longer clear although some objects may be discerned. Astronomical twilight is when the sun is more than 18 degrees below the horizon – complete darkness (apart from light pollution, of course)

Around the summer solstice here, we have a few weeks where there is no astronomical darkness. This is well shown on the “skylight clock” on the weather station web site.

Skylight Clock
Skylight Clock

Yellow is daylight with the sun above the horizon, the light blue is civil twilight, (sunset until the sun reaches 6 degrees below the horizon or from that point until sunrise), the mid blue is nautical twilight (sun reaching 12 degrees below the horizon) and the dark blue is astronomical twilight (the sun reaches 18 degrees below the horizon). Black is darkness. The red hand indicates what time it is relative to this. At the time of writing, there is a sliver of black left on the clock, but this will soon disappear until the evenings begin (slowly) to draw out in July.

All this affects nature. Animals (and small children) go to sleep later and get up earlier. Most British animals are crepuscular: being most active through twilight and in the morning and evening. As people tend to stick to the clock, we miss their most active times through this period of the year. perhaps we should get up and go to bed with the sun, but have a sleep in the day at this time of year!

Two bright meteors

Early this morning (22 Feb 2015) my camera recorded two bright meteors. These are not connected, but it after weeks of cloudy skies and very little activity when it was clear (this is the quietest time of the year for meteors) it is nice to have captured two impressive meteors.

Bright FED Meteor - 00:28 22 Feb 2015The first was at 00:28 (UTC). This is probably a February Eta Draconid meteor (see here for details of this recently discovered meteor shower) and had a magnitude of -3.4 making it about the brightest thing in the sky. The path appears to be curved because of the wide angle lens in the camera. In fact, the meteor passed almost overhead here – its path started above the North Downs and ended over the South Coast. It was still probably about 35km high when it burnt out.

Sporadic Meteor: 03:39 22 Feb 2015The second came in at 03:39 and was a sporadic – not associated with any known meteor stream. It had a magnitude of -2.9:

 

Both meteors show a small explosion during their path.