Earthshine

Unlikely at this stage. We could see a return to a Nino-like pattern with low pressure to the SW again. With extreme heat building in Iberia currently we could be in for a surprise. I guessed a CET of 18.1°C next month since I think the first week/third will drag the mean down.

Bloody hell, as bad as 2012? Not convinced by the longer range ECMWF anomalies?

Come on, 17.2°C for the win please!

Yeah I know, but I would imagine assimilating observations sourced around the UK would have a larger impact. E.g. AMDAR data I think only comes in during the day.

Sure, the USA obs will be during night time but the UK obs should still be assimilated in the period before 18z. It seems modern data assimilation schemes have eliminated the inter model run verification variability.

Brilliant, thanks! Looks like two extremely good runs around mid-May and earlier this month. I did notice just how close the forecast for the low in the Bay of Biscay and high pressure further NE verified a week later.

Makes sense, I would imagine the highest density of observations would be during the morning/day and hence initialising the 18z run closest to the "true" state of the atmosphere. Aircraft observations would be a big part of this I reckon, especially for upper air obs.

Does anyone know what the verification stats are for the different model runs (e.g. 00z vs 18z). They will surely have different quantities/qualities of observations during the 12 hour assimilation window previously (or whatever window the GFS uses).

During WW2 the UK was under a period of "double" summer time, winter was GMT+1 and summer was GMT+2. This resulted in lovely 11pm sunsets in summer and not-so-lovely 9:45am sunrises in winter for Glasgow, for example: https://www.timeanddate.com/sun/uk/glasgow?month=6&year=1944

A Westerly pattern with the 20°C isotherm over the south. Wow

I expect SST will continue to increase through the summer. The reason they are usually cool at this time of year is due to significant lag. There is a huge amount of energy being absorbed by the oceans at the moment, exacerbated by increased greenhouse gas emission, reduction in sulphur dioxide (IMO 2020 regulation changes), etc. Think the CET could be held up quite significantly. Even if daytime maxima aren't particularly high the absence of anything remotely cold (bar northerly winds) will prevent the CET dropping much at all. I expect the chance of having all three summer months recording a 17°C+ CET is as high as it's ever been!

There was a rise, 16.6°C now.

Hang on, I think I know the CET for this competition month. July 2022 was 18.2C!

Generally unspectacular synoptics but such warmth around the UK we end up with an 18C+ month!

Oops! Here's a fun one too, anyone ever see a Spanish Plume be launched out of the west coast of Portugal into the mid Atlantic? Like someone knocked the bunsen burner over!

Stonking GFS OP 18z run tonight. Potentially blazing hot conditions in Iberia this weekend with up to 45°C forecast in parts of Spain and Portugal, concerning heat. Let's see if it has support from it's ensemble friends.

Going with 18.1°C and 50mm. Warm SST will limit just how cool any westerly spells are and I'm keeping an eye out for some quite extreme heat to build into Iberia - should we tap into it we could really see some quite high temperatures that would be less modified by sea temperatures than you might expect.

We are in uncharted territory at the moment. Considering SST don't peak until late August/September time we could be in for some surprises. Minimum CET records to go perhaps?

N Atlantic SST anomalies are currently unprecedented, way above anything in recorded history. Much of the ocean/sea around the UK is suffering from a category 4/5 marine heatwave (extreme).

That's assuming the June and July&August CETs are correlated physically. We are seeing unprecedented SST anomalies across most of the N Atlantic, up to 5°C above average. Even a Westerly type pattern will see temperatures much warmer and humid than you would usually expect.

16.5°C to the 18th now. Mean maximum CET up to 22.6°C (1976 was 22.5°C).

I think people are getting a bit carried away with individual ensemble's at very long lead times. The mean for next weekend from both the ECMWF and GFS looks fine to me away from the far NW. 10°C 850 hPa isotherm across the south.

First half of August 2020 was very good here. Although it broke down quite significantly in the second half. September 2020 had some good warm spells too.

So far this decade we've had two pretty warm Augusts. 2020 and 2022 had CET values of 17.7C and 18.7C respectively. I wonder when we will see the next 19C+ August. If I were betting I would say before 2030.

GFS 0z ends with extremely hot air perilously close to UK shores. If that cut off low was any further west we'd be looking at 40°C being challenged again for the start of July. Extreme heat is likely to build into Iberia so any plume setup will be far hotter than usual IMO