Overnight site specific forecast temperature errors 25 Sept 2018

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Sep 25, 2018, 4:04:28 AM9/25/18
to Weather and Climate
Widespread reports this morning of low minima and light frost due to radiation cooling under clear skies.
Leafing through the MO site-specific verification page-
there appear to be some large errors in screen temperature forecasts. At 07 UTC mean errors:
Heathrow +2.6C (unusually large error for  this location in my limited experience)
Church Lawford +3.5C
Milford Haven +2.6C
Mount Batten +4.0C

Watnall +1.2C
Attached Watnall ascent tephi 00 UTC showing the near surface inversion, stratification and a strong PBL top inversion at 800 hPa.
It seems that despite major efforts the UM still struggles with this difficult problem- mixing down of warm air in a strongly stratified boundary layer.


George in Edinburgh

Sep 25, 2018, 5:44:24 AM9/25/18
to Weather and Climate
A useful link. Thanks

George in Swanston, Edinburgh


Sep 26, 2018, 4:09:05 AM9/26/18
to Weather and Climate
Most overnight verification locations much closer to obs this morning except Mount Batten which has a mean bias of +3C at 07 UTC.
Very dry air and a strong inversion near the surface on the Camborne ascent.
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