Gravesend 32.3C, why so hot?

Posted: July 19, 2014 by tchannon in weather

The Met office Gravesend weather station is a little notorious as runs hot in what is the hottest part of the UK where there is a lot of history over dubious temperature measurement. (some findings yet to be revealed)

Image

This Gravesend station is one of the few which regularly tops daily readings. I was prepared so I ran a capture of the Met Office web site hourly data for England, numbers are then plotted here. No better information is published, nor is this a full weather station, a subset.

What happened turns out to be interesting.

First so that anyone really interested can see all here is an automatically created PDF (399k) for all the England stations

Surface station articles and WUWT
https://tallbloke.wordpress.com/2012/09/11/wmo03784-gravesend-broadness/
https://tallbloke.wordpress.com/2012/08/17/gravesend-broadness-mystery-of-the-hot-met-office-station/
http://wattsupwiththat.com/2012/08/18/how-not-to-measure-temperature-part-93-the-hottest-weather-station-in-the-uk-cited-by-the-bbc-has-some-interesting-exposure/

There is a break in all the data, probably came over a telemetry radio network and breaks are common, particularly weather related. This might be a clue, atmospheric conditions.

If you look carefully at the Gravesend plot you will see an abrupt 90 degree wind shift, to due south and also an approaching minor low pressure centre. Shortly after it spiked hot. This is unique to the station, no wind shift eg. at Shoeburyness which is close, but some to the south and west show a hint of the same thing.

Gravesend station is located at sea level on the Thames with Kent/Sussex to the south then the English channel and the currently hot continental Europe.

Yesterday airflow carried lofted French humidity north leading to characteristic night-time thunderstorm. Same tonight, is gently flashing and rumbling as I write this, been a few drops of rain. Later it will go bang. A more severe plume runs to the east of here, hits London and Kent. (satellite images will show the “puffs” of convective cloud over France)

This was not so far as I know present during the middle of the day, was warm, upper 20s here. Current satellite imagery from the Met Office shows it was clear IR and visible. (copyright prevents me showing this)

Went out in the car about 20 hours, temperature was a steady 24C, hot and sweaty. Chilbolton peaked about 25C, wasn’t much different here. (think I saw 24.6C not that it is accurate)

A peculiar factor vaguly claimed sometimes by the Met Office is some kind of Föhn at Gravesend. No humidity data, so that clue is out. To get a Föhn it would demand rain over the quite small land rise to the south. I have no data but didn’t notice anything on radar. More likely is simple heat scour from the inland area.

There seems to be a connection between these abrupt wind shifts and extreme heat, could drag up other instances.

Can anyone else offer more insight?


The Met Office are offering Datapoint, some kind of API on published data. Doesn’t seem to do a great deal and copyright is vague. This might be a better alternative but as ever I have to write the code, doesn’t fall out of trees. I registered for an API key, of course they want to control everything whilst providing as little as possible. This leads to a reluctance on my part. Anyone with experience of using this and know the current copyright in simple terms?

Post by Tim

Comments
  1. The declination of the moon crossed the equator headed North on the 16th, will be maximum extent North on the 23rd, I suggest this is a lunar tidal effect on the frontal boundaries in the area at the time.

  2. tom0mason says:

    Some say tis the heat from all those rotting plague bodies at “Potters’ Thatch” that keeps it warm.
    In reality the heat is from the excessive smugness generated from not being London but having property prices that are.

  3. catweazle666 says:

    Back when I were a lad, most years it used to get hot in July, we called it “summer”.

  4. tchannon says:

    City / docks is close, unknown site and equipment.

    Was record there for Wunderground, 31C (METAR quantised to 1C)
    Met Office daily extreme reports use peak reading any second during the day, occasionally from human read glass later but that should be to at best 0.4C, (BS specification for the recent glass, IIRC use .0 or .5)

    The wunderground plots show the same sudden wind shift to south and rise in temperature.

    Met Office sites to the south are few.

    Herstmonceux shows a slight wind shift earlier, peaked 25C or so.
    Site moved to edge of field/wood I think.

    Kenley, southern outskirts of London shows a slower wind shift, maybe 28C

    Langdon Bay, Dover, clifftop, more severe wind shift, closer to the low pressure centre, 25, 26C later. Screen was dubious location, was photo in Dover planning documents, seems to have gone AWOL since post.
    https://tallbloke.wordpress.com/2012/08/27/wmo03796-langdon-bay-kent/

    Manston to the east had a wind shift much later, horrible site for this with a huge black runway to the south, maybe 30C, suggesting hot continental air off the North Sea

    Shoeburyness out east and north, much the same.

    South Farnborough, much as Kenley (close).

    Charlwood in the hedge (near Gatwick), gradual wind shift, maybe 30C
    See Colin Wernham’s lovely photos of the site in comment, Met Office’s finest. Pallet site as are many recent.
    https://tallbloke.wordpress.com/2012/09/09/wmo03769-charlwood/

    Be other stuff if you site search

  5. Kelvin Vaughan says:

    It’s the metal fence surrounding the site which will be very hot in the sunshine. Horizontal radiation will be bouncing back and forth across the grounds. Any breeze across the site will be heated by the fence.

  6. ntesdorf says:

    This could have been due to the temporary installation of a CAGW heater near the recording station by BOM staff.

  7. tchannon says:

    Next day was cooler, reported hottest St James’s Park, London, 28.5C the only synoptic site where I did not publish. A very large article exists, complicated where the history matters, what is not obvious.

    As I mentioned at the end of the article above I’m looking at the Met Office datapoint service. In context hourly station data is available for the past 24 hours. The station list is longer than I’ve been able to show via the Met Office web site, with some surprising sites but also omissions, such as St James’s Park

  8. tchannon says:

    Kelvin Vaughan says:
    July 19, 2014 at 8:32 pm

    It’s the metal fence surrounding the site which will be very hot in the sunshine….”

    Fences do alter conditions and the Met Office are notorious for installing high metal fences around sites. The degree of effect is uncertain.

    On screen I have a photo of an historic site in the north of England, copyright so I cannot use it here. There is a probable 6-8 foot high fence with 2 inch or so square steel supports and solid steel bars, in a park. The Stevenson screen is near to a stone monument.
    In this case I expect the screen was erected by the local town/city council, their kind of monstrosity.

    The photo is remarkable for showing dense frost on the park grass but little inside the met enclosure and essentially none close to the steel fence.

    Here we are if this works, Lister Park, Bradford
    http://www.bing.com/maps/?v=2&cp=sz21fpgvjyxd&lvl=19.28&dir=269.44&sty=b&ss=yp.lister%20park~pg.1~rad.80&form=LMLTCC

    Image rotate will vary the apparent height of the fence. It is tall.

    Static image here on Flicker
    Weather Station, Lister Park, Bradford

    The site has varied over the past 100 years, skyline trees, water, were no tennis courts and so on. History is critical with all sites, the devil to find and confirm.

    A little digging, a kind of view from inside the enclosure
    http://www.bbc.co.uk/bradford/content/articles/2008/11/17/lister_park_weather_feature.shtml