Looking back at satellite imagery from noon today, I can see the shadow cast by cirrostratus which was keeping the sunshine hazy where I was even as the sky became clear overhead. This is with the sun at its highest point of the day. Low rider!

There's growing confidence that ~29th Nov will see a major sudden stratospheric warming event, but one where reflection of wave activity in the stratosphere allows the polar vortex to quickly rebound. OTOH, most runs still have it anomalously weak in the 2nd week of Dec.

To visualise the effect of El Niño & La Niña, I decided to try applying a linear detrend to the ERA5 global mean temperature dataset, then plotting it against the annual mean Oceanic Niño Index. The result is an astonishingly good fit to a polynomial with 3 degrees of freedom.

There was quite the jump in temperature at Bournemouth Airport between 2 am & 3 am last night. 8.7°C in the space of an hour!

My current thoughts on the first ~week of December in Europe. Events in the tropics look to drive a build of high pressure across Europe, then try to shift that northward. Meanwhile, events in the stratosphere will probably favour low pressure in the Greenland-Iceland area...

A polar vortex of confusion simonleewx.com/2025/11/20/a...

With the much colder weather of late, November's Hadley mean central England temperature to-date has begun to nosedive & is down from 1st to 5th warmest on record as of 19th. Signs are it could drop to around 14th before a possible late recovery via an onset of milder weather.

With all the "will it, won't it" talk regarding a possible major sudden stratospheric warming event late this month, this seems a good time to highlight this excerpt from A. H. Butler & E. P. Gerber 's 2018 paper on the definition of such events. journals.ametsoc.org/view/journal...

Keeping an eye on potential for strong wind events to affect NW Europe - mainly UK & Ireland - late this month. Forcing from tropics will be trying to build high pressure over Scandinavia, but a lobe of the polar vortex in the stratosphere *might* aid dev of lows in N. Atlantic.

At 10+ days lead time, we're probably going to see all sorts of 'wacky' model forecast scenarios in the coming weeks - & not just cold ones. E.g. this GFS 12z with a strong blocking high over NE Europe producing well above normal airmass temperatures across much of N Europe.

Even with today's properly cold wind, it looks like the max temp here in NE Dorset will be around 5.5°C. It takes a lot to keep it much lower at this time of year. Within the middle third of November, only once since 1994 has the max been less than 5°C (4.4°C on 20th in 2004).

Had a quick look at how date records have shifted over the past 5 decades in my local area. Most striking is that the 2020s already have the largest share of date record highest max temps, & have just 4 record lowest max temps so far. Highest rainfall on track to rival 2000s.

Last night saw a low of -3.3°C here in NE Dorset, which is 0.1°C above tomorrow's date record low (1943-2024). That's as close to a new one as I've seen here in years. Incidentally today's date record low is -5.1°C, which is also the week-around-day record low.

Signs are, whether it qualifies as a major event or not, the sudden stratospheric warming to end November will be of the sort that displaces rather than splits the polar vortex (shaded blue). Importantly, this means surface weather impacts are likely to begin 2-4 weeks later...

On course for hardly a cloud in the sky here in NE Dorset today, a feat last manged on 25th Sep, although 30th Sep wasn't far off. Since then, not one day has been more than about 3/4 sunny (until now). A big contrast to the spring & summer which featured 34 clear days here.

Reflecting on the record-warm first half to November here once more, 2025 also set records for the most daily max temps >= each of 13, 14, & 15°C, & for the most daily min temps >= each of 11°C, 13°C, & 14°C. What a contrast much of this week is set to be 📉

Will it, won't it? The potential major sudden stratospheric warming event (i.e. reversal of 60N zonal mean zonal wind at 10 hPa) has proven difficult for the forecast models to resolve. Having initially converged on ~27th Nov only to back off, now ~29th Nov is the proposed date for a reversal.

Winter approaches, with yesterday's highest UK temperature the lowest since 17th March (12.1°C at Achnagart), & lowest temperature the lowest since 20th March (-7.9°C at Braemar).

Yesterday saw an interesting step-change in forecast modelling for the week after next in NW Europe, from a mild & dry outlook to a chillier, more unsettle done. With the polar vortex being substantially disrupted, I expect there's plenty more forecast volatility ahead.

Forecast modelling is keen on a high amplitude, slow moving MJO event in phases 6-7 for late November into December 2025. With a La Niña in effect, this has historically tended to result in both high pressure & cold weather extending westward from Scandinavia.

Major sudden stratospheric warming dates & types in records back to 1958. The vast majority are within January-March, while the earliest on record is 28th November in 1968. Current forecast guidance suggests 2025 *might* see one on 26th November... a new record if it happens.

Quite surreal walking in sunshine at 17°C in mid-November here in NE Dorset. Some of the local deciduous trees are still hanging onto plenty of green leaves.

Currently approaching 17°C here in NE Dorset, which means the 1943-2024 date record high of 17.4°C is within reach, which also happens to be the record for the calendar month too. It's been recorded twice, once on 5th in 1946, then again on 13th in 2022.

The forecast model consensus for tomorrow's wettest weather is now further north than most of yesterday's runs had it. Result being, southernmost counties look to be spared the worst of it, but 40+ mm in 24 hours may be experienced as far north as Leeds.

The Hadley mean Central England Temperature was the warmest on record for 1st-11th November, at 3.4°C above the 1991-2020 average. Signs are it should remain so through today, before starting a decline that could prove quite steep for a while.

Following a slight trend colder in the forecast, it seems next week may in fact bring conditions supportive of lowland UK snowfall even in the south. BUT having that coincide with precipitation looks a bit of a long shot. Even the usually over-keen GFS ensemble is far from emphatic.

Rainfall so far this autumn in my local area has been very close to the 1991-2020 average. Yet it's felt pretty soggy to me, which I can attribute to the very dry spring-summer combination, & goes to show how biased memory can be, as last autumn was absolutely soaking here.

This month has so far averaged a daily maximum of 14.9°C in my local area, which is the highest for 1st-11th in records back to 1943. There's not been much sunshine to enjoy that with though, with 2025 the 4th dullest on record with 21.7 hours. Last year was on just 2.5 hours 😵

Still a question over how far north in Wales & England the wettest weather occurs on Friday, with some 50 miles of difference between ECMWF & ARPEGE. In the peak swathe, exceptional amounts look localised if any, but 50-60 mm could cause some (mainly 'surface water') flooding.

I've been hesitant to talk about colder UK weather next week, due to poor forecast confidence (huge spread) plus little sign of anything all that interesting for lowland areas. Even the coldest ECMWF ensemble runs are barely cold enough for snowfall in Reading for example.

Had a go at mapping historical Hadley mean central England temperature data to the potential impact periods of major sudden stratospheric warming events (based on literature), while grouping into displacement & split type events. There are some clear differences between them...

2025 delivered the warmest 1st-6th November in the 254-year Hadley mean CET series, knocking 1996 down to 2nd. For 1st-7th, the record highest is nearly 0.5°C lower. Today is extremely mild again for the CET region. So we can expect that record to be well beaten by 2025.

A wide area of the SE US below 0°C. Meanwhile, my local area in CS England has yet to drop lower than 2.5°C (36.5°F) this season.

Unsurprisingly, 2025 is doing battle with the likes of 2010 & 2015 for the title of mildest opening stages of November on record in my local area (& likely many parts of the UK). For up to 6th Nov, 2025's in 2nd place. Outlook is very to extremely mild through at least next Thu.

My experimental 'temperature extreme index' represents where this year's observed temps are in relation to the long-term average (index 0) & weekly record high (1) or low (-1) values. Where it exceeds 1 or -1, new weekly record highs or lows were set (5th Nov, new night high).

A 'negative North Atlantic Oscillation' (NAO) pattern is characterised by relatively high pressure in the Greenland-Iceland area & low pressure nearer the Azores. It's often considered a bearer of cold weather for NW Europe, yet this isn't always true, as next week will demonstrate...

Just realised there was a date record highest minimum here in NE Dorset last night, 13.7°C comfortably topping a 12.9°C in 2010. However, when looking at a weekly window around the date which is arguably more meaningful, 2010 is still on top with a 13.9°C on 3rd Nov.

Interesting to see so many ECMWF ensemble members producing a major sudden stratospheric warming event, where the 60N zonal wind at 10 hPa reverses, in late Nov or 1st half Dec. In records back to 1959 I'm aware of only 3 major SSWs within 1st half Dec & none in November.

Some notably high temperatures for the time of year in northern Europe this week. Hints of something similar for western Europe later next week too, but uncertain how far north or east it reaches, with colder conditions attempting to advance from the north instead.

I've had little to say about the Hadley mean Central England Temperature this month & with good reason - it's not been very interesting! Since 2nd it's always been among the warmest 56 on record, but never ranked higher than 31st. Looks to finish ~0.5°C above the 1991-2020 average, ~40th warmest.

Hurricane Melissa will pass near Newfoundland on 1st Nov as an ex-tropical cyclone, then head toward the Iceland/UK area. This flings a lot of warm, moisture-laden air across Europe. Unusually low heating demand for early Nov, but also a risk of excessive rainfall in the north.

With hurricane Melissa, we've seen a near-worst case scenario in terms of intensity & cumulative impact on land areas 😔 A larger, comparably strong hurricane tracking its eye just west of Jamaica, then just west of Manzanillo, would perhaps be even worse. Hopefully never to be.

Melissa's second landfall, just west of Santiago, has for the most part put it up against similarly rugged terrain to what it encountered in western Jamaica. However, the western flank of its circulation is traversing some even higher mountains, which will give it a hard time.

If this 892 mb reading is confirmed by the NHC, Melissa's min. sea-level pressure will have matched that of the 1935 'Cuba' hurricane (no official name in database), as the 3rd lowest on record for an Atlantic basin tropical cyclone. 1st is Wilma 2005 (882 mb), 2nd Gilbert 1988 (888 mb).

Insignificant compared to its imminent impacts on Jamaica, Cuba, & Haiti, but I'm keeping an eye on the potential for (ex-) Melissa to throw some exceptionally warm air (for the time of year) across northern Europe next Tue-Wed.

The western end of Jamaica where #Melissa is projected to make landfall has the least well-built structures of anyplace on the island. Graphic is from a 2021 paper, "Poverty and hurricane risk exposure in Jamaica": www.researchgate.net/publication/...

An update to the Atlantic basin first 5 hurricanes mean peak wind speed graph. This season has no reliable precedent. It's a tragedy that 2025's strongest will not only have the largest area of direct impact on land, but do so while at or close to its peak intensity.

Caveats apply with the pre-satellite era data, but from the information available in the IBTrACS v4 database, 2025 has set a new record for the highest mean peak wind speed of the first 5 hurricanes in an Atlantic season at 143.8 mph, edging out 1999's 138.1 mph.

The 2025 Atlantic hurricane season is now on a below average 5 hurricanes, but an above average 4 major hurricanes. In the IBTrACS v4 database I can only find two other seasons since 1900 on 5 hurricanes, 4 majors up to this point: 1909 & 1948. None were on 6, 5 or 7, 6.

Melissa's slow crawl while strengthening to category 5 is very reminiscent of Dorian 2019, except the eyewall is thankfully not impacting any land areas. Sadly, it's forecast to turn toward Jamaica tonight & make landfall there tomorrow... as a category 5. Stay strong, Jamaica.