Weather in 2014

The weather station began to operate in August so I do not have data on a full year yet, but I thought it might be useful to mention a few figures.

Temperature

The highest temperature was 27.2C at 15:00 on 18 September and the coldest was -5.1C at 07:33 on 31 December. 18 September was the only day when the temperature was above 27C (or 80F). The highest minimum was 15.9C on 6 August ( an uncomfortably warm night) There were 13 air frosts (2 in November and 11 in December)

Wind

The strongest gust of wind was 47kts (54mph or 87kph) at 03:41 on 12 December. December was the windiest month too.

Rainfall

It rained on 82 days (out of 153 recorded days). Six of these days had more than 20mm rain and 49 more than 2mm (which is what most people would notice as “raining”). November was the wettest month with 156mm, but October was close behind with 147mm. The wettest day was 23 November with 29.6mm.

All the data recorded by the weather station is available online at its own web site: weather.curtisfamily.org.uk. Complete data in table formats is available at: http://weather.curtisfamily.org.uk/NOAA-reports.php and here: http://weather.curtisfamily.org.uk/detail.php and in graphical format here: http://weather.curtisfamily.org.uk/wugraphs.php

Sprite - 8 November 2014 at 03:37GMT

I captured sprites!

My meteor video system captured sprites early on the morning of 8 November 2014.

Sprites are one form of transient luminous event or upper atmospheric lightning. In the upper atmosphere, very high above active thunderstorms, there are various forms of electrical discharge (sprites, elves, blue jets and even gnomes and pixies!) that are poorly understood and which were not even recognised until the last 20 years or so. In the last few years, it has been realised that video systems designed to capture meteors may also capture these fleeting phenomena which seem to occur at similar heights to meteors. Early this morning, my meteor camera caught two (and possibly three) sprites associated with thunderstorms that were over Northern France and the English Channel (120 – 150km away from here) at the time. I am thrilled to have video of one of the atmosphere’s most elusive sights.

Jet

At 03:20 the system captured a “columnar sprite” or possibly a “blue jet” (Clearly visible in the lower centre of the image captured from the video). As I look at the video in detail (frame by frame) I can see a very faint general flash along the lower right of the screen one frame (1/25 second) before the sprite appears. I think this was the very distant lightning reflected in clouds that were just below the horizon here and possibly from some clouds that are just visible in the image, between here and the storm. (The video camera is extremely sensitive, so this seems possible. Lightning is easily bright enough to be seen from 150km away at night if you are high enough. I was once thrilled to watch from the window of an airliner at night as lightning coursed backwards and forwards through a line of towering African thunderstorms. The captain reassured us that we were over 100miles away from them). The sprite lasts three video frames or 3/25th second, with only one frame being bright as shown in the image. A blue jet is emitted from the top of the thunderstorm cloud, so this is more likely to be a column sprite – an emission high in the upper atmosphere (perhaps up to 100km) above the storm.

The video shows a very much fainter sprite happening about 1/5 second before this one, to its left and lower down.

At 03:37 (see main image) the system captured a classic “carrot” sprite – very clear and bright. Again, it is possible to see a brightening along the horizon, which I assume to be from lightning, about 1/25 second before the sprite appears. This sprite appears on four video frames (4/25 second in total). The central column appears first then the “carrot”. Like lightning, sprites are a very short lived phenomenon.

Such sensitive video systems are very noisy – the backgrounds look like snowstorms, and trying to convert the video to web format makes it even worse. I will try to process a viewable video and share it. On my computer, it is possible to work through frame by frame to see the details. The sprites are fairly bright. If you had been looking in exactly the right place (and had you eyes open and focused at the split second the sprites occurred) you could have seen them with the naked eye.

I have reported the sprites to researchers at Bath University, as well as to the UK meteor network.

 

Windy

Today is the windiest it has been since I set up the weather station at the beginning of August. Top gust so far is 33kts ( 38mph or 61kph  a near gale) and the average wind has been at Beaufort force 4 (moderate breeze) for quite a lot of the day. Nothing extreme here, but the liveliest yet. The weather station is in the garden – fairly sheltered – so official wind speeds are likely to be higher. This is simply a typical autumn storm as a low pressure area sits on top of us. As well as the wind, this gives the unstable and showery, even thundery, conditions.

Meteor Video


I made a video from one of the captures by my automatic meteor camera. This is basically the raw video from the camera, with a little noise reduction and colorising the monochrome video to a blue hue. This is real time video (not slowed or sped up). I shared it because I thought it was a particularly pretty meteor.
It was a brightly moonlit night and, as you can see, partly cloudy. The bright star in the lower centre of the image is Aldebaran – the brightest in the constellation of Taurus, the bull.
The meteor analyses as part of the lambda cygnid meteor shower. This is a minor shower, possibly associated with debris from a minor comet – 2005CA. Details of this meteor (and all others observed) are in the ukmon archive.

Classic Cold Front

Today’s weather came from the passage of a cold front: where cold air pushing in, lifts the warmer, moister air in front of it, to create rain. Although the front was not particularly remarkable, it fitted the textbook very well so is worth reporting.

Noon Met Office Analysis Chart - 4 Oct 2014 Firstly, the analysis chart shows the situation. Over Europe there is still the high pressure which has dominated our weather for some time, bringing light winds from the south and south-east. This air has been in place for a while, so was warm and humid. The air held quite a lot of water moisture, but there was no rain as the high pressure meant that air was descending and there was no mechanism to lift the air to create clouds and rain.

Behind the cold front, a very different air mass is pushing in from the atlantic. The air is much colder and so holds much less moisture. The front is where the colder air is pushing at the warmer air, lifting it from the surface and so making rain.

That’s the “synoptic view” (which means “seeing it all”). What did we see here in Horley, on the ground? My weather station saw a sudden drop in temperature, a sudden drop in dew point (which reflects how much moisture is in the air) and a change in wind direction. There was also a sudden increase in wind speed at the front itself.

Temerature Change There was a drop in temperature from about 14C to about 10C over less than an hour. The dew point dropped from about 15C to about 10C in the same time. A clear change in air mass.

 

 

Wind speed
Wind direction

 

The wind speed peaked and the wind direction changed at the same time. This was when the bulk of the rain (3mm of the total of just over 4mm today) fell.

 

After such a long period of dry and warm weather, it is tempting to see this clear event as the arrival of autumn. We shall see.

Perseid Meteor

Meteors

I took this photo while I was asleep! More accurately, it is a processed capture from an automatic system. This is a perseid meteor, passing close to the Pleiades.

I am now running a video meteor observation system and am proud to contribute the data to the UK Meteor Observation Network (ukmon). There is a basic cctv camera, fixed so that it is pointed SSE and up towards the sky, housed in a proper weatherproof case. The video is fed to a cheap usb video capture card and then to the same PC that runs the weather station. This runs software from the sonotaco group in Japan. The software receives the video and records it continuously, discarding it continuously 30 seconds or so later unless it has detected specific kinds of change in the shot – i.e. a meteor travelling across the frame. When this happens, the recording is sent to a file and details of the time are logged. Later, other software is used to analyse the meteor trail to calculate its exact position against the sky. When the data is shared, software is used to match observations of the same meteor from more that one site. This allows highly accurate positions to be calculated for the meteor and even allows its orbit to be determined.

It is surprising how many meteors the system captures: well over 200 in the six nights it has been running (which have included quite long periods of cloud). It helps that this is the peak of the perseids meteor shower. Although the full moon has interfered, I have been delighted to see how many meteors have been captured and down to about magnitude 2.

As well as video, the system captures a snapshot of the meteor. All snapshots, and details of all the meteors captured, are at ukmon:

Horley Meteor Station Archive

I will post some more videos of the more spectacular meteors on this site from time to time.

blue sky with high clouds

High Summer

July has been an almost perfect summer month this year. We had lots of sunny, warm and dry weather but also a few thundery breakdowns, which included a few classic summer thunderstorms here. We avoided the flash flooding and other nasty consequences that hit others and so were happy to see them go past. It now looks as if things are going to change as we go into August, though we are unlikely to be too wet here.

Southern England can be oppressively humid in the summer, but this has been fairly manageable in the last few weeks.

The weather station is fully set up, calibrated and operational. I cleared all the data at midnight to remove false readings (e.g. “rainfall” recorded by jiggling the sensor when putting the weather station in place) and so that the data is genuinely comparable from day to day. The weather station is in proper operation from 1 August 2014.

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Weather Station installed

Thanks to the amazing generosity of staff, students and parents as I took early retirement from Headship, I was able to buy a Davis Vantage Vue weather station, which is now working in my garden.
The garden and other local gardens have quite a lot of trees and so are sheltered. Ideally, a weather station should be more exposed to “see” the weather more clearly, but it is measuring what the weather is like here.
The sensor pod communicates wirelessly to a console in the house. In turn, this connects to a PC that processes the data (using the excellent Cumulus software) and uploads it to the web site. The data is also sent to the Met Office, to NOAA in America and to Weather Underground, as well as making an hourly tweet.

Weather Station

I do not have any weather station hardware yet, but I wanted to make a start on a project to create a weather station for home. I want to keep an accurate and reliable record of the main weather data but also share them – through a web site and direct to various agencies so the data is useful. (e.g. the Met Office WOW programme or Weather Underground)

I found out about Sandaysoft’s excellent cumulus software and have it set up and adapted the web pages slightly to echo the rest of my web site. Obviously, no weather is yet being measured, so no valid data and no updates. That will come in time. Watch here for more news.