Penellype's Weather Channel

[Penellype]

Pen,
I know anything more than a week away is subject to rapid change but do you with your vast weather knowledge think that this type of weather might come to an end in a couple of weeks?
Our thermometer, in the shade is reading 32C at the moment and the local news is saying that the heat is just practicing for Thursday or Friday.

My OH has severe chest problems and the heat is making him virtually immobile.
X

I know it sounds like a cop-out, but I really don't know. We are in any case at the hottest time of the year and the ground is very dry which means that it heats up rapidly in any sunshine. The current hot weather is caused by high pressure which runs through the atlantic, over us and joins with a high over Scandinavia, which has basically been there pretty much since March. This sort of pattern is hard to shift. Currently the heat is being fuelled by somewhat lower pressure to our west, which sucks up air from the south or south east between the low and high areas, which means either directly over us, or slightly to our east. The runs that are producing the possibly record breaking heat are bringing the hot air from the south directly over us - these have backed off a bit for now but may return.

Thursday/Friday/Saturday looks like very hot followed by thunderstorms which are likely to be rather more widespread than those we have had so far. However, the high pressure to the east remains stubbornly in place, preventing the low from moving through and away to the north west and introducing cooler air from the west. Instead the low is pushed north and the ridge of high pressure rebuilds from the south west, and starts the process all over again.

The GFS model is the only one that goes beyond 10 days. This is seeing on average a continuation of the heat, although individual members of the ensemble do cool down at times, so there is a lot of uncertainty and scatter.



Personally my untrained opinion is that to shift this "stuck" pattern into a cooler one we need an ex-hurricane to head in this direction, as this would possibly have enough energy in it to disrupt the high. Possibly - hurricane Chris had a go a while back, and failed. There are currently no hurricanes forming in the tropical atlantic, and the accuweather hurricane centre says "There is a very low chance of any noteworthy tropical development for at least the rest of July." However, I could be wrong, and things could evolve into a cooler pattern on their own.

[Lumpy]

Thank you Pen.
I trust your analysis far more than the tv people.
X

[Penellype]

The TV people are professional forecasters and know a lot more than I do. However, they are constrained by having a short time in which to convey a lot of information covering a large area in which there may be several quite different sets of conditions. They tend to concentrate on large general areas with vague descriptions such as "north" or "west". Often, for example, there is one weather or temperature symbol covering the north east, ranging from southern Scotland right down to the wash, whereas in reality York can have very different weather conditions from Edinburgh, Newcastle or Hull. There simply isn't time on a TV forecast to go into detail for every area. They are also talking to a wide audience, most of whom probably have little interest in high or low pressure, jet streams, ex hurricanes or ensemble runs. They don't really care why the weather is doing what it is, they just want to know if it will be hot or cold, wet or dry and possibly windy, thundery, snowy or icy.

I like to try to explain why, because it gives people a better insight into whether or not what they see in the forecast is likely to be reliable or not. For example today, anywhere south and east of a diagonal line through Newcastle down to South Wales and Devon is going to be warm to hot, anywhere north and west of it is cooler, due to the presence of a weak cold front along that line. Anywhere along that line and slightly south of it may or may not see showery rain from the front, behind it in the cooler area there may also be showers, but these are very scattered. Many of the showers may also be evaporating in the heat before they reach the ground. So the temperature is easy to forecast, but the rain is not.

[Lumpy]

Thank You.

[roitelet]

Fascinating Pen, thanks.

[Gillykat]

I've been given next week off so I'm all stocked up on Factor 50, got my alarm set for 5am (cooler!) and will spend the week making serious inroads into the mess that I call an allotment!

[Penellype]

The forecast for this part of the country has suddenly got rather wetter (last 2 runs of the models) for the weekend. It is hard to tell if the rain forecast is just showers or a band of rain from a front associated with the low just to the west, which is forecast to move closer now than it was earlier in the week.



It will still be very warm or hot tomorrow and Friday for southern and eastern areas, with potentially mid to high 30s in the south east and eastern east anglia on Friday. It is possible that the July record temperature of 36.7C could be broken if the sun stays out for long enough before the heat triggers storms. The all time maximum UK temperature is 38.5C (101.3F) from 10 August 2003.

The storms and low pressure will result in a cooler weekend with north western parts seeing some quite autumnal-feeling weather with a westerly wind and temperatures in the teens. However the south, in particular cities, will remain warm as the heat will take some time to be released from bricks and concrete, which act like storage heaters.

The heat and dry weather is forecast to return next week as the basic pattern remains very similar. The latest run of the GFS has next Thursday and Friday very hot indeed (30C here, and you can add a couple of degrees to that), but as with this week's heat, the exact positions of high and low pressure will be critical in deciding who gets hot and who gets wet, and will be subject to change until the last minute.

[Penellype]

The weekend is now looking much wetter almost everywhere than it was a couple of days ago. The difficulty is forecasting how quickly the low pressure and associated troughs and fronts will move across, and unlike runs earlier in the week which showed this struggling, the models are now suggesting the low moves right across the country. Hot and humid weather with storms in the east and midlands later today and tomorrow (not everyone will get one), which could be intense with heavy rain, hail, thunder and potentially tornadoes, especially in the north east. These will be followed by a cold front with a band of more general rain, probably clearing into the north sea during Saturday and followed by much cooler, fresher air with some showers. The heat is currently expected to build again next week with a return to dry conditions, but at least everywhere should get some ran this weekend.

Keep an eye on the radar as these storms are a "nowcast" situation. Forecast rainfall totals for specific locations from weather apps etc could be wildly out (by several inches in extreme cases). There is enough energy in the atmosphere for storms this afternoon in the whole of England apart from the south west, so a rogue storm could pop up anywhere, but the eastern side has a convergence line which provides the necessary trigger for potential storms, hence the area covered by the yellow warning https://www.metoffice.gov.uk/public/...ate=2018-07-27.

[Penellype]

I should perhaps mention that winds will be rather stronger over the weekend than we have had for some time. Keep an eye on the forecast as predicted areas of strong gusts are changing with the model runs, and make sure things like garden furniture are secured.

[Nicos]

Yikes!
Thanks for the warning....we've had a tent/pergola type thing up for a few days now so will certainly need to keep an eye on that, otherwise it'll end up somewhere across the valley!

[Chippy Minton]

32C here this afternoon with the CumuloNimbuses (CumuloNimbi?) building up. Could be a downpour, could be just a humid night.

Been working in a school which was surprisingly air-conditioned. Had rather a shock when I walked out!

Must.........................have............................rain......................

[Penellype]

32C here this afternoon with the CumuloNimbuses (CumuloNimbi?) building up. Could be a downpour, could be just a humid night.

Been working in a school which was surprisingly air-conditioned. Had rather a shock when I walked out!

Must.........................have............................rain......................

Very hot and sticky here, and a few storms rumbling about (but only about 5 minutes of rain so far). By the end of the weekend most places should have had some rain. This is the accumulated rainfall from the Arpege model to 6pm Monday:



I must admit to being somewhat taken by surprise by this low pressure moving through this weekend!

[Penellype]

Where has the August heatwave gone? Models have suddenly backed off the extreme heat for next week:



Compare with the prediction from 2 days ago:



Still not much rain in the forecast after this weekend though, the change is due to a change in forecast position of the high pressure.

[Penellype]

Be careful what you wish for!!!

Shortly after I posted the above post it started to rain. I was aware that there were storms coming, and as usual I unplugged everything I wasn't using and connected my computer via wifi. We had a useful amount of rain, but unfortunately the lightning struck one of the nearby houses. I think it must have caused an electrical surge because there was a bang and my power sockets downstairs all went dead. I tried to reset it in the fuse box, but the switch refused to stay up. I called an electrician who fixed the problem, identifying the culprit as the fridge. However, he wouldn't test the appliance (not his job), so I was left with no fridge. That is currently being sorted.

I plugged things back in and found that my internet router and my backup internet router (which I really should have unplugged, but its a pain to do so) are both dead, even though they were on a surge protected extension lead. I've ordered a replacement for the main one, but it won't be here until Monday. I'm on my "last resort" mobile dongle at present, so please bear with me if things don't get updated as often as usual.

When it happened I was eating my breakfast, planning my day and feeling 100%. I now feel sick, shaky and drained of any energy, so whether that's just shock or whether I took some current from the lightning through the ground I don't know. Its completely messed up my day though and I doubt I will be doing any gardening today.

Stay safe in those storms, and unplug important equipment if thunder is close!

[Lumpy]

Just seen that the Met office have upgraded storm warning from yellow to amber for parts of Lincolnshire and East Anglia.
Gulps loudly and starts pulling plugs out.