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Gravesend Broadness - 34.4 on 13th Sept


yorkschris

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I always think there is something very strange about Gravesend Broadness.  It seems to feature an incredibly large amount of times in the list of 'highest' (sic) temperatures in recent years and has done so again this week - 34,4C on 13th.  A general concern I have is that instinctively it does not 'feel' like the location you'd expect to see the highest temperatures.  Typically in the London area isn't it stations more to the west and 'inland' you'd expect to be the warmest - not least because winds in heatwaves tend to be from the south to east quadrant?  The other point is that the location of Broadness is right at the end of a peninsula jutting out into the Thames - where are the 'sea/river' breeze effects you might expect?  Viewing the location of the station in 'Bing' appears to show an industrial type location, possibly enclosed in embankments and close to tidal mudflats -not exactly the most neutral location.  In addition, it was low tide at the time of the highest temperature on 13th September - coincidence?  The other thing that does not stack up is that if you check on 'Underground' there are many amateur stations that typically read higher (some times much higher) than professional Met office stations in warm conditions - yet on 13th September the typical temperatures they were showing close to the Thames in North Kent and South Essex was 30-32C.....  There is something very odd if not 'fishy' about this site and the record temperatures it keeps recording

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire

That particular reading was a nonsense, without a doubt. It somehow jumped more than 2c over half an hour when we were already at peak heat. 

You would have thought that the Met Office would ensure that all its sites were not prone to such issues.

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Posted
  • Location: Aviemore
  • Location: Aviemore

What's more odd on this occasion is that the highest temperature in the hourly series that are published from it was 32c, recorded at both 13 and 15z. So it must have leapt up and back down again inside the space of an hour to record 34.4c. 

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Posted
  • Location: East Devon
  • Location: East Devon

I agree it's a bit suspect but can't agree it's 100% nonsense just because it jumped up and down a couple degrees within an hour. Such things occur occasionally especially near coasts/estuaries with mixing of air from different sources, I've seen bigger variations on both my station and official stations due to this.

I posted a possible explanation in the Autumn thread, To go into further details:

The slight ENE breeze during the observations would have probably come off the estuary/river, so if a brief change of wind direction occurred to say the SE, slightly hotter air could have conceivably come over the site briefly?

Notice how at 5pm, the wind turns ESE and the temperature rises back to 32.0C despite it being about 2 hours before sunset along with a drop in humidity from 47% to 34%, and it's still 30.5C at 6pm. Yet when the wind switches back to NE at 7pm it drops very quickly to 24.0C (yes that's near sunset but it would probably not have jumped downwards that quickly on it's own, nothing like that the day before).
This and the more humid air when the wind was ENE suggests it may have a more maritime (and therefore slightly moister/cooler) source.
A brief change in wind direction could have conceivably happened earlier in the afternoon between hourly observations.

Of course to the ENE is the Thames estuary, while to the ESE is the part of Kent where the UK's high temperature record was recorded.

However, the fact that this temperature seems above any other official stations, including several nearby personal sites on Wunderground makes me more suspicious (i.e where did the hotter air come from? A local effect perhaps)

Despite this, a couple nearest stations show a peak of around 33C ( 33.8C on one station) between 2-3pm associated with a brief deviation of wind from ENE to SE/S! Relatively 'smooth' temperature curves may suggest a slow response time compared to official sites and/or insufficient observation resolution (I am ignoring any Netatmo stations in the area which are terrible for response).

My 'gut' feeling though is that it's a little high and there is something about the site, and a brief wind direction change caused these to affect the reading as well as perhaps a slight genuine increase in temperature.

Sorry, a bit of a rambly post but my ideas above seem hypothetically possible to me.. would be interested in thoughts and if anyone thinks it's not.

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Interesting ideas, 'Evening Thunder".  Definitely something odd at this site.  My quick examination data on Wunderground of six amateur weather stations close to Gravesend Broadness showed the following:  Mean Max of the six stations on 13th 32.1C and on 14th 28.4c; Maxima at Gravesend Broadness 34,4 and 28.2C.....  So on the 13th Broadness was 2.3C warmer than the mean for six other sites in the local area, but on the 14th it was 0.2C COOLER??  I still don't understand why such a weird location was chosen by the Met Office and why its rather anomalous readings still get into the official record books..... Seems to me that the Met Office has spent recent years casting aside a lot of historic records that came from stations where it considers the high temperatures anomalous (even if they were measured in Stevenson Screens eg. the record of 35.6c from Gunby, Lincolnshire in July 1959), yet Gravesend Broadness similarly gives these odd readings on certain hot days.

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

The biggest short-distance temperature contrast I ever recorded was 11C - from +6C at Drumnadrochit to -5C 7 miles up the road...

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Further to the Broadness issue.  It's difficult to get a clear picture from the satellite of the nature of the geography of the location but from the large scale OS map it looks as though the Met Office monitoring site at Gravesend Broadness is located within a small 'bowl' of land, enclosed to North and East by embankments and then - across a creek to the south - by more embankments.  The creek itself would appear to be dry mudflats at low tide ....  A really very strange location for a met office monitoring station and likely to produce some atypical readings I would have thought.  

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Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

Hottest station again today:

 

Anecdotally, I've noticed Writtle seems to record an inordinate number of high maxes and low mins in East Anglia. 

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.
8 minutes ago, Yarmy said:

Hottest station again today:

 

Anecdotally, I've noticed Writtle seems to record an inordinate number of high maxes and low mins in East Anglia. 

Hot-/cold-spots can also depend on soil structure, especially in a year in which rainfall totals are variable over very short distances: sandy soils dry much faster than loam or clay? I say that because, here, we've enough rain (thunderstorms/downpours) to keep most (not all) of the grass green...Maybe Gravesend has missed-out on its usual rain? Writtle, in contrast, hardly seems to have featured in this years' maxima...Maybe, it got lucky with rain, too?:D

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
23 hours ago, Yarmy said:

Hottest station again today:

 

Anecdotally, I've noticed Writtle seems to record an inordinate number of high maxes and low mins in East Anglia. 

Writtle is just outside Chelmsford..i wouldn't class Essex as East Anglia

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Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL
4 minutes ago, cheeky_monkey said:

Writtle is just outside Chelmsford..i wouldn't class Essex as East Anglia

Neither would I, but the Met Office do. To me East Anglia = Norfolk and Suffolk, with perhaps just a bit of Cambs.

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Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
1 minute ago, Yarmy said:

Neither would I, but the Met Office do. To me East Anglia = Norfolk and Suffolk, with perhaps just a bit of Cambs.

Met office should stick to forecasting the weather obviously geography is not their strong point.

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Posted
  • Location: Edinburgh (previously Chelmsford and Birmingham)
  • Weather Preferences: Unseasonably cold weather (at all times of year), wind, and thunderstorms.
  • Location: Edinburgh (previously Chelmsford and Birmingham)

I actually emailed the Met Office about this just after it happened, and yesterday I received a reply.

"The following is from a climatologist within our National Climate Information Centre.  

I agree that the difference between the highest hourly value and the daily maximum seems quite large. However we have studied the 1-minute data from Gravesend and are confident that the observations are correct. What appears to have happened is that the wind direction veered from around 60 degrees to around 120 degrees for a period of around 20 minutes (between 14:10 and 14:30) and that as a result the temperature rose fairly steadily to eventually reach 34.4 deg C and then dropped away again. It seems to be coincidence that this peak occurred between two successive hourly observations.

I will discuss this with my colleagues and hopefully we will be able to add another graph and/or commentary to our event summary to provide support for the observations.  This may take a week or so. For information, the existing summary is here:

http://www.metoffice.gov.uk/climate/uk/interesting/september2016_temperature "

 

Hopefully that should clear things up.

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire
On 16/09/2016 at 16:36, cheeky_monkey said:

Met office should stick to forecasting the weather obviously geography is not their strong point.

Well if you actually look at their website, they describe the region as "East of England", not East Anglia.

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Posted
  • Location: South Norfolk, 44 m ASL.
  • Weather Preferences: Varied and not extreme.
  • Location: South Norfolk, 44 m ASL.

Further to the question on the Gravesend station, the following (from reliable Youtube videomaker Tom Scott) may provide further information:

https://www.youtube.com/watch?v=ML5TaNlwgeg

As to the question of soil types, any viewer of BBCs eastern England regional news will be aware that Santon Downham in Breckland frequently features at the top of the daytime maxima and night-time minima charts for the region.  This is due to the light, sandy soil in the Brecks which heats rapidly on sunny summer days, and cools rapidly on chilly nights.

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire
3 hours ago, knocker said:

 

I'm starting to become more convinced it was real then. But why can't we see this data real time? Many personal weather stations do!

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