Here's the Nottingham sounding for noon yesterday:
Code:
03354 Nottingham Observations at 12Z 03 Oct 2005
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PRES HGHT TEMP DWPT RELH MIXR DRCT SKNT THTA THTE THTV
hPa m C C % g/kg deg knot K K K
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1018.0 117 12.2 8.4 78 6.84 260 3 283.9 303.0 285.1
1017.0 125 12.0 6.0 67 5.80 263 3 283.8 300.1 284.8
1007.0 208 11.2 7.2 76 6.36 298 5 283.8 301.6 284.9
1005.0 224 11.1 6.9 75 6.25 305 5 283.8 301.4 284.9
1000.0 266 10.8 6.2 73 5.98 295 4 283.9 300.8 285.0
994.0 316 10.4 5.4 71 5.69 286 3 284.0 300.1 285.0
977.0 459 9.2 4.7 74 5.51 260 2 284.2 299.8 285.1
943.0 751 6.6 3.3 79 5.16 355 5 284.5 299.2 285.4
927.0 892 5.4 2.6 82 5.00 359 5 284.6 298.9 285.5
925.0 910 5.2 2.5 83 4.98 0 5 284.6 298.8 285.5
890.0 1224 2.2 1.9 98 4.96 346 7 284.7 298.8 285.5
887.0 1251 2.0 1.8 98 4.92 345 7 284.8 298.8 285.6
873.0 1379 1.3 1.0 98 4.74 335 4 285.3 298.9 286.1
850.0 1594 0.0 -0.2 99 4.46 345 8 286.1 299.0 286.9
847.0 1622 -0.3 -0.5 99 4.38 346 8 286.1 298.7 286.9
844.0 1651 6.2 -0.8 61 4.29 347 9 293.2 306.0 294.0
836.0 1729 7.1 -5.0 42 3.16 350 10 294.9 304.6 295.5
833.0 1759 7.4 -6.6 36 2.81 348 10 295.6 304.2 296.1
801.0 2080 6.2 -14.8 21 1.52 332 9 297.6 302.5 297.9
779.0 2307 5.1 -15.1 22 1.52 320 8 298.8 303.8 299.1
773.0 2371 4.8 -15.2 22 1.53 324 8 299.2 304.1 299.4
762.0 2487 4.6 -18.4 17 1.18 331 9 300.2 304.1 300.4
749.0 2626 3.7 -19.3 17 1.11 340 9 300.7 304.4 300.9
724.0 2900 1.9 -21.1 16 0.99 320 13 301.7 305.0 301.8
The inversion, a strong one as you can see, was just above the top of the cloud as usual. I think the 400 ft/degC approximation tends to work well in unstable conditions when air parcels rise from the surface under convection, and cool to their dewpoint. Yesterday it was neutral below the SC, and it was also quite humid close to the surface, giving an anomalously high dewpoint.