Exeter No 2 – A detailed review of one hour in the life of an official Met Office weather station…..or two. Does this explain PRT Spikes?

When I first reviewed the weather station at Exeter Airport I noted (as Tim channon had before me) that this screen location could under certain circumstances readily detect transient heat blasts from taxiing and taking off/landing aircraft. I also noted that this is a relatively new location (No 2) with the original site located at the opposite end of the runway and on its southern side at the “traditional” style of location alongside the control tower. The old site no longer archives any data for comparison to be made by the public with its new partner. This report was rapidly compiled with the assistance of Dr Eric Huxter and a third party with intimate knowledge of Exeter Airport who wishes to remain anonymous. The purpose is to consider the possibility of extraneous heat effects on yesterday’s reading at Exeter Airport for readers to consider. All evidence is circumstantial and I would welcome any debate regarding it.

To begin with why is there any concern regarding the accuracy of the above national highest reading of the day? What first caught my eye was the unusual spikiness this reading represented when viewed on the timed readings output shown on weatherobs.com. Spikiness of this sort is actually quite frequent here and is not reflected in the readouts from nearby private weather stations (PWS) just a few miles distant from the airport. Reading frequency shown on weatherobs here is variously at 10 and 20 minute intervals.

Another point worth noting is the orientation of the landing strip below. The main runway is 08/26 which means that working from north as zero it runs from 80 degrees to 260 degrees which in turn translates to running east northeast to west northwest as per this compass rose indicator centred on the screen below.

More background data comes from the indicated wind direction and speed for the period in question which was from the SSE around to WSW throughout the hottest periods.

The exact timing of the high was supplied by Dr Huxter following his inquiry of the Met Office. Eric has compiled detailed research into PRT Spikes relative to CIMO siting requirements as well as localised extraneous heat sources and transient heat events. Eric’s supplied data included the exact minute of the maximum reading at Exeter from his research format.

“14/09/2026 Exeter (CIMO 4) 30m Est. 1944(LIGT Era) recorded 27°C at 12:55 GMT

3.9°C above Previous hour

<0.001% probability at CIMO 1

38.9% of Minimum Assumed Ventilation

Since 26/04/2025

15 days of data

Mean spike 1.4°C 

5.1% Probability at CIMO 1

Mean Wind 38.9%MAV”

We now have an identified time of reading of 27°C at 12:55 GMT 14/9/2026 . We can also see this was a very large increment over a very short period.

So now looking for further background information the “Table Data” for the nearest Private Weather Station to Exeter airport (just 1.5 km distant) in the village of Cranbrook looks like this; Notes these times are in BST and thus run from 12:43 to 13:04 GMT.

No sudden spike is visible in this time slot and recorded temperatures ranging from 25.2°C to 25.8°C are much lower than the airport.

Here is the data from another nearby PWS known as Rockbeare Weather also just 1.5 km distant. Again readings from 12:45 through to 13:05GMT are much lower and do not indicate any sudden spike effect.

So what could possibly have caused such a sudden temperature jump at the airport site which is known to regularly occur here simply from looking at the historic weatherobs graphs?

“I now present the, of course purely circumstantial, evidence M’lud.“

At 12:35 GMT Skybus8Y512 De Haviland DHC-6 Twin Otter arrived from Scilly landing into the wind. It disembarked passengers and took on new ones for the shuttle return trip to the Isles. It then taxied to the extreme eastern end of the runway to take advantage of the breeze now coming straight up the runway from the WSW.
Its path towards the end of the taxiway turning onto the runway would look like this below with the screen enclosure marked by the tip of the red kite mark

Turning onto the runway would be at a low taxiing speed of 10 knots meaning the propellers would be fanning the screen through the 140 metre long curve for about 30 seconds continuously. On take off under greater power there would have been further fanning onto the screen but from greater distance. Final clearance once in position would be quick (just a few minutes) for this regular “bus” trip type flight. The Skybus cleared the runway at 13:05 GMT.

“I put it, your Honour, that this puts the perpetrator at the scene of the incident at 12:55 GMT precisely”

Of course this is all conjecture on my part, though every piece of evidence is verifiable by online sources including aviation trackers for flight times. My more exact aircraft positioning information comes from a person on the ground with intimate knowledge of the site who has requested anonymity. The obvious question is whether or not being fanned by aircraft engines from at closest 60 metres would have an effect on the PRT and this brief transient effect recorded.

I leave it to readers to decide for themselves given the evidence I have put forward as a possible explanation for this spike reading.

I simply cannot be bothered to forward my posts to the Met Office for their comments anymore as they refuse to engage in dialogue with me. The Met Office could very simply dispel any debate by releasing the readings from the other Exeter weather station on the other side of the runway – if this spike were natural, that station would have responded similarly – though of course so should the PWS which are almost as close and clearly did not. Then again if there other site did not verify this spike……………..

Source: https://talkshop.blog/2026/09/15/exeter-no-2-a-detailed-review-of-one-hour-in-the-life-of-an-official-met-office-weather-station-or-two-does-this-explain-prt-spikes/