Fog in Exeter catches Met Office out

Dashed line approximate outline of yellow warning for fog

As suspected yesterday afternoon the area of fog outlined in the Met Office’s yellow warning extended too far north, and even though they issued the warning late (1332 UTC) they didn’t factor in the SC sheet that had been edging down from the northwest during the morning and possibly some slightly drier air. Instead of visibilities of 100 metres across Lincolnshire the visibility at Scampton at 06 UTC was 45 km, with little sign of any fog further north than Shawbury further west. Rather embarrassingly the yellow warning didn’t include Devon at all, where at Exeter airport, a well known and notoriously cold and foggy spot, visibilities were 100 metres this morning!
Whoever wrote the TAF at Coningsby at 0456 UTC where there had been fog earlier in the night is still being ultra-cautious and thinks there’s a 30% chance of fog reforming this morning. The UKMO models might be spot on with the speed of the jet stream at 30,000 feet, but they’ve never been particularly good at forecasting visibility and the extent of radiation fog on the ground.

TAF: EGXC 270456Z 2706/2724 VRB03KT 9999 BKN045 TEMPO 2706/2724 4000 BR PROB30 TEMPO 2706/2711 0500 FG VV/// PROB40 2718/2724 2000 BR PROB30 TEMPO 2720/2724 0300 FG VV///

Courtesy UKMO

Addendum

With the arrival of the first visible satellite image I can now see why the Coningsby forecaster was being a little cautious.

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