Okay well... a rough estimate using the GFS 00z and starting with the preliminary Hadley CET suggests that it will stay in somewhere the 17.7 to 18.0*C range out to 23rd.
This is higher than the runs of preceding days thanks to the ridge reaching further east for longer - a trend I've been observing with interest.
The ridge then becomes focused west of the UK for much of the rest of the month, but I consider this the Nina-like bias of the model showing its hand; any such ridge focus should be brief before things flatten out again (and then, next weekend or thenabouts, we finally get to try for the height rise right through the UK and on to Scandinavia).
The GFS 06z focused the ridge out west a bit sooner and was then quite similar to the 00z in keeping it there, so the associated estimate is cooler by around 0.2*C as of 23rd, but for the reasons given above, I'm more sceptical of this run than I was of the 00z run.
The ECM 00z had a more realistic quick eastward return of the ridge.
Could we still possibly finish at 18.2*C or above? Well... if my estimates are in the right ball park*, then it seems feasible if we get a full-on plume from the south or southeast that spanned most of the final week. Ensemble modelling has yet to really go for a plume even arriving to begin with, though - just some exploration of the potential here and there. Such a lengthy event would be exceptional so it's not something I'd bet much on, I'm afraid.
If, instead, the final eight days were very close to the long-term average, the final CET would (again, if my estimates out to 23rd are near the mark) be in the low 17s - a reflection of the typical cooling via longer nights Gusty refers too.
Having posted all this, I expect the provisional will imminently be revealed to be several tenths too high to begin with
.
To be honest, after the big delay to the Nino-like pattern establishment by the unanticipated Pacific-Atlantic CCKW passage, I feared the CET would by this point have about half a degree Celsius more to make up for than appears to actually be the case.
* The nearest GFS grid point to Stonyhurst appears to be centred on terrain that's somewhere in the range of 100 to 300 m more elevated than the station location, the exact amount being uncertain as I don't have precise grid point centroid lat longs to work with. Just an impression from a high-resolution map. This means an uncertainty of about 1-3*C when interpreting the Stonyhurst values from the GFS data.
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2025's Homeland Extremes:
T-Max: 32.0°C 12th Aug | T-Min: -5.4°C 4th Jan | Wettest Day: 31.8 mm 18th Dec | Ice Days: None
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