FI Charts (T120+ onwards) Summer/ Autumn 2018 **READ MOD NOTE IN FIRST POST**

sdanseo wrote: »

A few runs in a row now on the GFS are showing almost an inverted version of the Omega block we saw a couple of weeks back.

Question for those more experienced here, what are the chances that the HP "wins" here and closes in that area of relatively lower pressure in the centre, thus putting us back in heatwave territory?

It's a matter of just how ridgey or strong the areas of high pressure are. On that particular GFS run, the low is forced southeastwards by the Azores High and Scandi High trying to conjoin with one another the day afterwards but a few days later, this doesn't come to full fruition as the westerlies take over. There are two possible reasons for this:

1. GFS' westerly bias
2. The temperature contrasts in the North Atlantic which I described yesterday powering up the jet stream.

The second reason is questionable on this run though because there is no retrogression of the high pressure up to Greenland and the jet stream is still quite a bit northwards.

Why this week's showers or rain from Wednesday to Saturday are uncertain or downgraded after looking like decent spells of rain, is as a result of the jet stream. It's still quite a bit to the north of us and it's weak in its current state regardless of Chris therefore, there is no "real areas of low pressure" to be seen and brought across the North Atlantic through us.

The models have really upgraded the heat overnight for next weekend and beyond with heatwave conditions again likely to take place over the UK and Ireland though as you'd expect by the timeframe, there are some differences among the models. Here I discuss what the latest runs of the two models, GFS and ECMWF, show. The wording might sound a bit weird since I originally made it for my blog which is for both the UK and Ireland.

The GFS 06z shows high pressure from the Azores ridging to us by Saturday 21st July which gradually over time pushes to our east and draws in a southerly to southeasterly flow with hot air from Europe. Low pressure is stalling in the Atlantic as a result of this area of high pressure and if that low were to invade a few days following the establishment of hot weather over us then there'd be some severe thunderstorms. This is a proper hot scenario with temperatures easily getting into the 30s across England and Wales whilst mid to high 20s over Ireland and Scotland. If the wind was to sustain a southeasterly airstream along with the high pressure not going too far east, then 30°C is not out of the woods for Ireland.







ECM 0z is kind of different. It ridges in the high pressure similar to the GFS during next weekend (even hotter air on this model) but the jet stream is closer to the north of Ireland and over Scotland. This would mean it'd be cooler and cloudier up there with temperatures stuck in the high teens and low 20s mainly in any sunshine but generally mid to high teens. Elsewhere, we'd be talking mid to high 20s and low 30s over England & Wales. The high pressure also doesn't push east over to Scandinavia, it stays over top of us. The heatwave conditions dam line (564) is across Ireland on Saturday on the ECM whilst it makes its way to most parts then afterwards.

ECM 12z goes the high pressure route though at +192 hrs, it goes a bit "wonky" in weakening the high pressure along with looking like cool 850hPa temperatures coming down from the northwest but at the end, there is a thundery trough just to the southwest of Ireland with both countries in a hot plume of air.















Different solutions are still being thrown around as shown from the 12z runs so none of this certain and is to be taken with a pinch of salt for now.

After a warm weekend, the GFS 06z brings down a cold front for Monday into Tuesday next week which will bring cooler temperatures again for a time and some light rain. After that, high pressure starts approaching from the south (again) and ridges to the east with low pressure stalling to the west by Thursday forcing the wind direction to go into a humid southwesterly to southerly. This goes on for a few days before low pressure successfully makes it through. Very hot temperatures over the UK in that kind of setup and evident of a heatwave whilst for Ireland, mainly around the high teens out west and low 20s elsewhere though possibly higher once the sun shines. The GFS 0z was very similar.



GFS 06z ensembles are in agreement at +240 hrs as shown by the chart below. The first ensemble diagram is for London whilst the second and third ones are Dublin and Cork respectively. Just look at how much the white line (ensemble mean) is above the red line (30 year average) for London. Some real serious heat coming to them if the GFS 06z ensembles are correct. Even if it's not as warm here as it is there, it will be very humid!









ECM 0z is similar to the GFS but it delays the real push of heat for the UK for a day whilst low pressure anchors itself over Ireland.





Still all to play for it seems.

ECM 12z is warm again. Tuesday's cold front pushes southwards for a time but then can't budge much further thanks to the blocking area of high pressure to the east and gets shoved back westwards or fizzles out. The Atlantic trying to come back but just doesn't on this ECM run with a low just out to the west whilst the wind is coming from a southerly direction drawing in hot, humid air. This is mainly to England but even Ireland would be warm widely in the 20s and humid.

Yes if the Scandi High gets going we could be in for a repeat of August 1995.

Its a very mixed picture of charts. One run hot one run not so hot.

Remember the middle of June they promised an end to heatwave but then it reappeared in the charts a few days later.

Definitely think England is due some real heat still this Summer if not us. Think away from North and West will definitely get warm spells of sunshine and these areas too on specific days.

Looking at charts there certainly could be another 30c somewhere in Ireland yet in the coming fortnight. But rain too at times mainly in more Western areas.

daphne wrote: »

I see MT Cranium says that we are going to get some proper rainfall 27th July-1/2nd Aug... are the runs now converging on that?

Well they have shown that around day 10 of the charts several times but it hasn't materialized.

His forecast of 50mm from those dates is very interesting and will give a lot of farmers some great hope!

Not sure I would be brave enough to forecast it mind

sryanbruen wrote: »

To prove how the GFS (other models too) hasn't got a clue, here's all its runs since 0z on Tuesday (up to 06z today) for 14:00 on Thursday 26th July.

Throughout my life if we are having a wet summer and models are showing an anticyclone over Ireland in 7 to 10 days after a run it seldom materialise to be true. I think the opposite is happening this summer. A low pressure system is either downgraded or replaced with high pressure as Sryan demonstrated in a few posts above.

12Z ECM shows much of the same as what we have for the next 10 days, mildly warmer Sunday and Monday then back as we were.

Then the following weekend the Atlantic very much wins. Very little precip up to 25th and then pow, we get 30mm.

As Sryan said though - FI is not much past 3/4 days. This is 9/10, so large tub of salt.

Since you brought up the ECM, well here's every ECM run for the same time period (26th July) since Monday. It has been far more consistent than the above GFS runs but still not "brilliantly" consistent to really grow confidence. Notice on the ECM charts though the lack of northern blocking.

The teleconnections support more of the same of this Summer but.... there are some spanners in the works like potential tropical developments, Pacific trade wind bursts etc.

I think theyr topsy turvy coz a change is coming and they dont believe it.

Theres been rain in Sligo on all days this week bar one.

Jetstream is back home

Normal Summer service has resumed.

Still at least went on holidays in dry spell.

ECMWF has mived the trough slightly further west which could see most of the decent rain confined to western areas though.

UKMO brings it closer though so still a lot that will change.

The ECMWF Clusters showed a bring spread behind +240 and I wouldn’t like to try call that.

Yup, as I begin to lose hope the 06Z GFS throws up this short oven blast!





Look at those temperatures over Paris!

It's 10 days out and quite an outlier so I'd say quite unlikely. However something in the 30's is likely.

In contrast to the 06z, the GFS 12z shows no plume for the UK and the heat is far more sensible. High pressure starts building over Ireland too. Next runs are likely to change again knowing the inconsistency of every run of the GFS recently.