Latest Arpege 30c for Monday 33c for Tuesday. Crazy for mid September.

 

33C would blow the date record of 30.6C for the 15th out of the water.

I think perhaps we need a heat potential thread!

---

Looks like we may get 19 C!! It's a SE Britain affair once more

---

Looks like we may get 19 C!! It's a SE Britain affair once more

19C is pretty good for Edinburgh in September.

---

Looks like we’re going to get that rare beast, which shows up frequently on charts but seldom actually happens: the sinking post-plume low pressure.

Happens as follows:

- Plume brings up hot air from the south
- Low pressure sits out to the west
- Instead of sweeping across us bringing cool air, it sinks southwards
- High to the East links up with high in N Atlantic, bringing Easterlies and extending the settled spell

There are 5 evolutions from a plume: 1. the Southwesterly thundery breakdown followed by low pressure parking over Britain bringing downpours; 2. the Northwesterly cold front sweeping chilly Atlantic air across the country; 3. the stalling and retrogressing of the low bringing even hotter weather; 4. the partial zonal incursion with the low slipping Northwards and keeping things dry in the South, and 5. the sinking low and anticyclonic join-up that we’ll see next week. 5 is probably my favourite.

---

Bone dry GEFS this morning. Remarkably so, in fact.

---

 

33C would blow the date record of 30.6C for the 15th out of the water.

I think perhaps we need a heat potential thread!

I think we need a stickied climate change thread.

---

A nice warm September extending into October leading to a dry November, folllowed by a deep freeze in December would do nicely.

Too much to ask?

Bone dry GEFS this morning. Remarkably so, in fact.

And a month’s worth of rain in parts of NW Scotland over the next 2-3 days. Quite a contrast!

---

Jetstream running strongly across N Scotland for the next couple of  days (hence all the rain there) but forming a loop to the S by late Mon 14th which by Thu 18th has resolved into a cut-off low over Iberia and a waving branch up around Iceland. Mon 21st, two branches, one over the Med, the other in N Atlantic, the latter doing a repeat performance and spawning another cut-off low over Iberia Thu 24th but this time the low moves up to the UK instead of getting incorporated into the Med circulation by Mon 28th. There's still a N branch waving over Iceland.

GFS - W-ly turning SW-ly under influence of LP to SW by Wed 16th. This  LP wanders around over Spain and France to Sun 20th while an ex-hurricane (Paulette?) gets gobbled up by LP in N Atlantic. HP remains over Scotland to Wed 23rd while a new LP develops to the W (more warmth from the S) but this LP moves in over Ireland Sun 27th and HP recedes. A couple more ex-hurricanes out on the Atlantic by then but weakish and not affecting the UK.

GEFS - Peak heat on Tue 15th after which a steady decline to normal (smoother than yesterday)by Thu 24th - fairly good agreement on this. Odd splashes of rain from Sat 19th onward (less than yesterday) Scotland - a more irregular decline in temp, indeed some runs not declining at all, and apart from present rainfall in the extreme N, notmuch to be seen until some runs from Wed 23rd onward.

ECM - Similar but ex-hurricane Paulette is a bit closer and could affect weather in the N, but after that ECM ges for higher pressure more generally than GFS

---

Quick look through the GFS charts....a very wet South West event on the cards ?  Unless it changes somewhat the next heat breakdown does look different to most of the summer events.....subtle pattern change good to see in my opinion...

---

Tomasz Schafernaker said at lunchtime that the upcoming hot spell with temps of 30c in S.E. doesn't count as a heatwave. Really? Has GW changed our perceptions of a heatwave by that much? I think he must have been on the sherry.

---

Tomasz Schafernaker said at lunchtime that the upcoming hot spell with temps of 30c in S.E. doesn't count as a heatwave. Really? Has GW changed our perceptions of a heatwave by that much? I think he must have been on the sherry.

I think it needs to be 30 c at any part of the UK for more than three days to constitute a heatwave, this looks like being a two days warm spell - albeit  doesn't make it any less unusual given this this time of year.

---

16-dayer shows warmth this week though not so much in the NW, fading away to the SE. Fairly dry for two weeks, though a lot of rain over France could with a little shift threaten the S coast n week 2.

GFS - forthcoming  really hot spell shortening all the time and  beyond Wed 16th just pleasantly warm with LP off W Ireland moving to S of UK  with HP over Scotland  bringing in E'lies by Sun 20th, at the same time swallowing ex-hurricane Paulette so low confidence in its development. New LP off Ireland Thu 24th, situation looks like a repeat of next week briefly but this LP moves E-wards as a trough over whole of the UK. New ridge of HP Tue 29th. here's another potent ex-hurricane shown near Newfoundland Sat 26th but it's quickly extinguished.

GEFS - from 10C above norm Tue 15th a steady decline (as yesterday) in the S to seasonal average by Fri 25th; cool runs make an appearnce a few days earlier and most of the ensemble after that is on the cool side with much uncertainty. A fairly confident rain event for extreme S on  Sun 20th, and then increasing chances of rain through to end of run Tue 29th. Scotland never quite as warm, and drops off more quickly though again staying on the warm side of normal to the 25th. Rain on 20th is missing, but again chances of rain later on.

ECM - while generally similar to GFS, accentuates the HP over Scotland through to Tue 22nd and downplays LP to the S. Not so much a new defined LP on Thu 24th as a widespread decrease in pressure

---

Tomasz Schafernaker said at lunchtime that the upcoming hot spell with temps of 30c in S.E. doesn't count as a heatwave. Really? Has GW changed our perceptions of a heatwave by that much? I think he must have been on the sherry.

I assume that’s the official thresholds he’s talking about, which are intended to be for public health purposes. A couple of days nudging 30 with nights in the teens aren’t going to endanger life, so that’s probably the context.

My personal definition of heatwave has always been at least 5 days above 28 with at least 3 of those above 30. “Mini heatwave” being any spell that tops 30C in at least 2 places.

---

 

I assume that’s the official thresholds he’s talking about, which are intended to be for public health purposes. A couple of days nudging 30 with nights in the teens aren’t going to endanger life, so that’s probably the context.

My personal definition of heatwave has always been at least 5 days above 28 with at least 3 of those above 30. “Mini heatwave” being any spell that tops 30C in at least 2 places.

How do they class a classic summer??..the extreme south east havent done bad although I know it hasnt been a nationwide event

---

How do they class a classic summer??..the extreme south east havent done bad although I know it hasnt been a nationwide event

I don’t think there’s an official definition of classic summer, but 2020 certainly wasn’t one. Let down by July temperatures and June/July rain and cloud.

Classic summer to me would mean all major summer months warmer than average, at least one month above 18C CET, summer as a whole sunnier and drier than average, and at least one intense 35C+ heatwave.

 

---

I would say all time classic summers would include 1976,95,03 and 18. That's 5 in my lifetime! In terms of winters you'd possibly include 78/9 but really it would be 62/3 and 46/7 that stand out from the last century. Unfortunately I've not experienced even one if the marginal 78/9* is excluded. 

 

*I'd possibly put it into the classics but not the all time classics.

---

You forgot December 1981 with widespread record lows and 2010 which was not far behind.
78/79 was more snowy than 63 in some areas and it went on for weeks with almost no thaw here between Christmas and mid-March.

---

You forgot December 1981 with widespread record lows and 2010 which was not far behind.
78/79 was more snowy than 63 in some areas and it went on for weeks with almost no thaw here between Christmas and mid-March.

I didn't forget them. They were months not seasons. 

---

Well it was colder, cloudier and wetter than average here, so certainly not a classic. Today was nice though and the outlook is not awful even if there is an easterly influence.

(In contrast spring was warmer, drier and sunnier than average).

---