Stormy Weather II

[Serial_Apologist]

Tipping it down all day and pretty chilly too. Ideal day for decorating.

There has been a lot of mention about the massive rainfall happening over large parts of Scotland. What is unusual in this instance is that it is occurring along the pivot section of a frontal system, where the part of the front advancing SE in the wake of a departing low transitions into the warm front of an incoming low advancing NE. Usually this is the weakest link in the frontal chain, where the associated rain belt narrows and weakens, sometimes ceasing altogether. I would think there must be some additional forcing mechanism at work in keeping the convection line active along its entire length - probably an effect of orographic uplift where the oncoming south westerlies are being forced upwards by mountainous terrain, concentrating and increasing the moisture bearing content in the cloud band.

Down here it's just another lovely day, the edge slightly taken off the otherwise unseasonably high temperatures by cloud build-up in the middle layers (altocumulus) along with a fair amount of high level haze from imported Saharan dust, and a steady moderate breeze. So, not quite enough consistent warmth for indulging in any sunbathing today - maybe tomorrow, although I am hoping to take to the roads for what could well be my last chance to undertake a long cycle ride, destination Fulham Palace, where they do a nice tea with cakes etc on the terrace. I want to "do" the scenic riverside path from Fulham FC ground to Hammersmith Bridge, which I only discovered travelling in the opposite direction a couple of months ago.

I really hope your weather front gets a move on a.s.a.p. JC!

[Serial_Apologist]

Today's beautiful weather had me out on a 23-mile circular cycle trip, taking in the recently extended riverside path on the northern stretch of the Thames between Wandsworth and Putney bridges and ending up at the lovely Fulham Palace for tea and a delicious slab of flap jack topped with plain chocolate and nuts and large carton of tea. The place was proving a popular attraction in this luckily prolonged spell of late summer weather, as is the Wandsworth/Putney footpath, along the length of which walkers in groups were following the markings and sticking to the left both sides. The last time I took to this path a couple of months ago pedestrians and cyclists had barely discovered the route, but now that it sports several outside eateries and picturesque pubs its popularity is bound to increase, linking up with the continuation of the route NW beyond Hammersmith Bridge, which has always attracted the crowds. Temperatures reached 24C widely in and beyond London today, and a couple more days like this could well see October records broken. I only experienced two bottlenecks where I was forced to dismount and walk for about half a mile: along the Chelsea Embankment, where near stationary westbound traffic clung to the red curb line, and on the return crossing Battersea Bridge.

[Joseph K]

It's very still at the moment and already mild. Could reach 22 or 23 here later.

[Serial_Apologist]

It's very still at the moment and already mild. Could reach 22 or 23 here later.

At this latitude, longer nights and weaker solar power mean that local factors assume an increasing prominence over previously wider predominating influences when it comes to maintaining high daytime temperatures. Back let's just say 40 or 50 years ago it would have been rare to find daytime temperatures exceeding 17C other than in a mobile air stream of subtropical origin, because it would need that level of impetus to carry the warmth this far, even in southern England. Record high temperatures have been restricted to locations to the lee of high ground - notoriously north-east Wales and eastern Scotland, where the so-called Föhn effect, forced descending air under an inversion "cap", heats up by compression at a greater rate than on the ascending upwind. What nearly always happened was that inversion fog would form overnight in high dewpoint conditions typical of autumn when surface moisture persists because the sun's power was no longer strong enough to disperse, so it would linger on calm mornings, thereby shortening the period available for any remaining solar warming at the surface to take effect.

The present situation, finely balanced between sufficient inflow of warmth, nocturnal radiation and progressively lowering night time temperatures, and increasing incursions of cloud as the atmosphere destabilises ahead of change forming a trap to keep nocturnal temperatures relatively high, will resolve later this week as the Atlantic jet resumes and frontal systems sweep any residual warmth away. Incidentally it's noticeable that today's midday temperature here is a couple of degrees down on yesterday's, following a near-calm night.

[Joseph K]

At this latitude, longer nights and weaker solar power mean that local factors assume an increasing prominence over previously wider predominating influences when it comes to maintaining high daytime temperatures. Back let's just say 40 or 50 years ago it would have been rare to find daytime temperatures exceeding 17C other than in a mobile air stream of subtropical origin, because it would need that level of impetus to carry the warmth this far, even in southern England. Record high temperatures have been restricted to locations to the lee of high ground - notoriously north-east Wales and eastern Scotland, where the so-called Föhn effect, forced descending air under an inversion "cap", heats up by compression at a greater rate than on the ascending upwind. What nearly always happened was that inversion fog would form overnight in high dewpoint conditions typical of autumn when surface moisture persists because the sun's power was no longer strong enough to disperse, so it would linger on calm mornings, thereby shortening the period available for any remaining solar warming at the surface to take effect.

The present situation, finely balanced between sufficient inflow of warmth, nocturnal radiation and progressively lowering night time temperatures, and increasing incursions of cloud as the atmosphere destabilises ahead of change forming a trap to keep nocturnal temperatures relatively high, will resolve later this week as the Atlantic jet resumes and frontal systems sweep any residual warmth away.

I wish I had taken my phone with me on my walk for photos. The Lake looks really beautiful in this weather at this time of year - something to do with the particular height of the sun meaning light falls in an attractive way.

[Serial_Apologist]

I wish I had taken my phone with me on my walk for photos. The Lake looks really beautiful in this weather at this time of year - something to do with the particular height of the sun meaning light falls in an attractive way.

That angle of the sun necessarily limits safe cycling to cloudy days from now to early March. We don't have the limited benefit of windscreen visors, and then I wonder to what extent the incidents of pedestrian accidents with traffic are ascribable to sun blank out as compared to the clocks going back at the end of the month.

[Pulcinella]

After a couple of gloomy (but warm) days it's much brighter and even warmer (phone app says 22C) today: dishwasher load and washing load done, and solar battery at 98%.

[Joseph K]

Very misty & still right now. Looks like today is the last warm day, I'll take some pictures later today.

[Serial_Apologist]

Very misty & still right now. Looks like today is the last warm day, I'll take some pictures later today.

Make the most of today, anyone south of a line from Teeside to Merseyside; north of that..........

[Old Grumpy]

We just sneak in (I think)...


...forecast for bright, sunny days, but cooler (not cold!).

[Joseph K]

No pictures forthcoming, I'm afraid, or at least not today. It's not as sunny as yesterday...

[Petrushka]

Hazy sunshine here today. Comfortably pleasant in shirt sleeves for my daily walk. Looks like a nasty shock to the system coming at the weekend with a big temperature plunge. Some cold nights too.

[Joseph K]

Yesterday I thought was the beginning of the end for the warm weather, but the temperature was back up today, it is really quite balmy (outside much more than in) or at least was earlier - it's now raining.

[Serial_Apologist]

Yesterday I thought was the beginning of the end for the warm weather, but the temperature was back up today, it is really quite balmy (outside much more than in) or at least was earlier - it's now raining.

So did I (think Tuesday was the end of the warm weather), but there was some delay, and today a postponed end -of-season farewell toast to what has been a remarkable summer... I was going to say worldwide, but obviously only applying to the northern hemisphere. This year, unlike last with its record-breaking 40C + highs, marked something of a reversion to old-fashioned typical British summers, disappointingly cool and cloudy, but for once I would imagine that many witnessing the frazzling temperatures in Italy and Spain either directly or on their TV screens would have felt some relief.

Whether [sic] or not we have been in a state of grace might become known next year as a knock-on effect of the El Niño event now commencing in the tropical Pacific west of Mexico; the boffins are still looking into this. For the immediate future there's going to be something of a shock, starting from midnight, as winds swing around to north-west behind the very active cold front now evidently crossing the north and the west Midlands, bringing gusty winds and possibly half an hour of torrential rain (maybe thunder and even the odd funnel cloud), followed by a temperature plunge that will have already hit Scotland and much of the north and north west. High pressure then nudges in from the west from Sunday, and with it, since it is a "cold high", the first frosty nights in the usual suspect places.

[oddoneout]

Yesterday I thought was the beginning of the end for the warm weather, but the temperature was back up today, it is really quite balmy (outside much more than in) or at least was earlier - it's now raining.

Yes, it's been very warm here as well, I'd expected it to be cooler. Rain clouds gathered early afternoon and dropped a few warning splats but then thought better of it and disappeared; having to put a waterproof on was rather uncomfortable given the temperature at 21 degrees . The clouds are massing again now and are due to deliver something more substantial, and the temperature is due to nosedive as the sun goes down, in preparation for a chilly weekend. The "f" word has appeared, so I need to collect up my tender plants and find some fleece(just hope the mice haven't been nesting in it as they are wont to do) to cover them.