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

Lumi

Mod Note

This thread is for posting/discussing/analysing FI CHARTS ONLY i.e. Charts in the unreliable time frame, generally +T120 onwards

If your post does not specifically relate to an FI chart then it doesn't belong here - Off topic posts will be moved

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Mobhi1

Sammy2012 wrote: »

What kind of temps would be expected it that verifies??

Presumably up around 30. Maybe the record would be broken.

Donegal Storm

Temperatures would probably be similar to last week but far more humid so more of a tropical feel. It's followed by a day of intense thunderstorms then high pressure rebuilding once again in the third week of July

Kermit.de.frog

If that occurred temperatures inland would be reaching the low thirties. As mentioned some big thunderstorms would also move up from the south. It's just one of a number of outcomes though ranging from very warm to hot.

hatrickpatrick

Can someone explain one thing to a weather geek who still has a lot to learn

How is it that people can be predicting hotter weather with similar pressure heights going into July, and that one or two posters mentioned that "the hottest and stickiest part of the summer is still ahead of us" a day or two ago? I had always assumed that the heat potential in high pressure was at least partly related to the sun's position in the sky, so that the summer solstice (June 21) would be the day with the absolute maximum possible temperatures from sunny weather, and that going into July, while the weather can indeed remain more or less as epic as we've been having, a similar atmospheric setup to that which we've seen throughout June wouldn't be able to deliver anything hotter, seeing as the sun is slowly starting to drift away from its maximum height? So in other words, I had assumed that as far as anticyclonic sunny heat goes, June 21st is the "speed of light" of sunny weather if you will - no day can surpass it in terms of heat potential?

sryanbruen

GFS 12z seems to be going Spanish Plume route too.

Farmer2017

sryanbruen wrote: »

GFS 12z seems to be going Spanish Plume route too.

Can u please explain what the Spanish plume route means. Thank you

pad199207

sryanbruen wrote: »

GFS 12z seems to be going Spanish Plume route too.

I only like Spanish plumes if the pattern of hot and dry weather reloads again after it.

Meteorite58

This is far out in FI and anything could happen or not but the GFS 12Z chart look very interesting in that we get warm temperatures, a plume of high Theta E readings and the Iberian shallow Lp comes up to our shores from around Weds T+216 and in over Ireland. This could theoretically give rain/ convection / thunderstorms. Long, long way off yet though.

It finishes it's run with LP coming in off the atlantic at T+312 but that is way too far out to know and could be all changed on the next run..

sryanbruen

Farmer2017 wrote: »

Can u please explain what the Spanish plume route means. Thank you

A Spanish plume is when low pressure is just to the southwest or west of Ireland and high pressure lies to the east of the UK drawing up hot southerly winds from the Iberian Plateau. As the warm air moves northwards to us from Iberia, it will rise as hot air is less dense than cold air and condensation causes the formation of thunder clouds. The cooler air that comes from the west (the Atlantic) increases the instability in the atmosphere and the very warm air that ascended from Iberia rises through this cooler air which results in intense thunderstorms. Thunderstorms of course let out a lot of rain in a short period of time and sometimes, heavy hailstones can be associated with these thunderstorms especially in Spanish plume scenarios. For example, 1 July 1968 (exactly 50 years ago yesterday funnily enough) brought hailstones of around 7cm in diameter to southwestern England caused by the Spanish plume that occurred on this day. Spanish plumes also bring high humidity with them leading to very uncomfortable conditions especially at night.

Normally in these kind of scenarios, the Atlantic wins out, pushes the warm air away and we go into a normal zonal pattern which we're all familiar with in our country during most of the time. On the rare occasion, the Atlantic doesn't win and the high brings more warm, dry weather afterwards. This depends on the strength of the high pressure though.

This scenario on the GFS model is over 9 days away so it's out of the reliable timeframe and is all just speculation for now.

Meteorite58

Excellent sryanbruen !

PukkaStukka

Were Spanish plumes at play in the '85 and '86 events?

Victor Meldrew

So, is the Spanish Plume on the 11th our best FI chance for rain or is there an FI model where it turns to 15c and rain for a week....

Speak Now

Victor Meldrew wrote: »

So, is the Spanish Plume on the 11th our best FI chance for rain or is there an FI model where it turns to 15c and rain for a week....

I don't believe it (FI)

sryanbruen

PukkaStukka wrote: »

Were Spanish plumes at play in the '85 and '86 events?

Yes indeed they were, see reanalysis 850hPa temperature charts below for both events. Quite good examples actually! Spanish plumes are what thunderstorm enthusiasts dream of.

A recent example was that of 18th-20th July 2014 which delivered some scattered thunderstorms over Ireland though they were much more intense to eastern England where the real heat was with a max of 32c being recorded. This was an occasion where the high pressure was stronger than the thundery troughs so the Atlantic did not win out - at least for another week.

The ridges seem to be very strong and intense this Summer that I think if we were to have the Spanish plume, the ridging would take over the pattern again. The GFS is being too progressive as always in FI with the Atlantic taking over. I mean, a Biscay low winning out the battle against a 1025 to 1030mb block of high pressure? Like come on :P.

This is not likely to happen or affect us here in Ireland as it would in the UK but it's not impossible to happen so I'll go and say it. The 850hPa temperatures on these model runs to the south over Iberia are warmer than those on 10th August 2003 when the UK set their all-time highest temperature of 38.1c. These higher 850hPa temperatures combined with the very dry ground (also heated up ground from this Summer so far) would make for some real dangerous heat I would think with 40c (if those 850hPa temperatures would push up) not being out of the woods for the UK. Any attempt of cooler air from the Atlantic would make for some real epic thunderstorms in this heat as such happened on 10th August 2003 during that record temperature when Carlton-on-Cleveland in the UK recorded up to 30mm in 5 minutes.

Victor Meldrew wrote: »

So, is the Spanish Plume on the 11th our best FI chance for rain or is there an FI model where it turns to 15c and rain for a week....

As you live in Dublin, pretty much yes but there are very small chances of scattered or localised showers from Wednesday to Friday to occur. These are not likely for Dublin but ya never know with pesky showers so don't totally rule them out.

Nope, the general outlook is for anomalous blocking over top of us to bring a very dry and hot start to July through minimum the next 2 weeks. Key word: minimum, meaning longer is possible because this is an Omega block which is around the strongest type of high pressure you can get. In Summer time when the jet stream is weak anyway, this can be even more difficult to move. We're locked into this pattern for the foreseeable future unless something happens in the atmosphere to change it up and put a spanner in the works. This Spanish plume as I said in my explanation post is just speculation for now and discussing probabilities about it because it's showing up in the models - this is the FI thread after all.

Donegal Storm

Should be noted that Spanish Plumes, almost without exception in recent times, end up missing us and giving the UK and near continent a spectacular light show. I remember one in particular in 2012 I think where there was great excitement all week only for each model run to slowly push the heat further east. The UK had a spectacular supercell outbreak and we just ended up with a few pulse storms.

The rule book seems to have been thrown out the window recently though so who knows what'll happen

Kermit.de.frog

GFS for Sunday

Jet stream diverted well to the north through the Greenland/Iceland/Norway corridor

Farmer2017

Kermit.de.frog wrote: »

GFS for Sunday

Jet stream diverted well to the north through the Greenland/Iceland/Norway corridor

What’s does all this mean Kermit ?
Is it good or bad to have jet stream north ,

Ultimate Seduction

Farmer2017 wrote: »

What’s does all this mean Kermit ?
Is it good or bad to have jet stream north ,

Bad for you.

savj2

The jetstream is the boundary between the cool Artic air and warmer sub tropical air

As the Artic warms up in the summer the jet stream weakens

But to answer your question, the jetstream north means warm and dry conditions in summer.

Usually it's either slghtly over us, slightly under us or directly over us which is where we get those line of low pressure systems bringing rain and showers.

The 4 years in a row 2007 - 2011 where we got wash out summers the jet was I think slightly below Ireland bringing constant showers and cool weather.

Victor Meldrew

sryanbruen wrote: »

As you live in Dublin, pretty much yes but there are very small chances of scattered or localised showers from Wednesday to Friday to occur. These are not likely for Dublin but ya never know with pesky showers so don't totally rule them out.

Nope, the general outlook is for anomalous blocking over top of us to bring a very dry and hot start to July through minimum the next 2 weeks. Key word: minimum, meaning longer is possible because this is an Omega block which is around the strongest type of high pressure you can get. In Summer time when the jet stream is weak anyway, this can be even more difficult to move. We're locked into this pattern for the foreseeable future unless something happens in the atmosphere to change it up and put a spanner in the works. This Spanish plume as I said in my explanation post is just speculation for now and discussing probabilities about it because it's showing up in the models - this is the FI thread after all.

Thanks for the response, so basically this hot weather for ~ 2 weeks, some thunder showers, maybe, but they will not replenish reservoirs due to soil moisture deficit and may actually be counterproductive for farmers in being half hearted restarts of growth only for it all to wilt again.

So 2 weeks before even FI models shows normal wet weather. Kinda explains IW's panic.

Cheers for the detailed and patient post.

Kermit.de.frog

There is no "normal" Atlantic regime on the horizon at all.

The closet is thundery LP wandering up from the south in the 10 - 14 day range. That depends on there being some strength and right direction in the southern arm of the jet but there you are dealing with a split jet stream as well which is hard to model and fantasy stuff at this range.

I wouldn't be placing any bets on it!

cherryghost

A collective raindance might work.

All models are in agreement for 7 days+ which an astonishing feat itself. Temps reaching 30s again next week (maybe locally later this week too)

Kermit.de.frog

High pressure looking more intense by Sunday on this morning's GFS run.

Temperature records are again under threat with that.

Actually quite a severe run in terms of persistent high temperatures and drought for the next 10 or more days.

But chopping and changing to come yet...

Meteorite58

GFS well out in FI ( very unreliable timeframe ) showing more influence from the Atlantic. First with the Iberian LP throwing showers / rain bands our way and eventually moving up over Ireland at the end of next week. It would be moving into warm air and possibly ripe for thunderstorm activity if that warm humid air coming up from Africa can get into the mix . During this spell the charts are showing the Jet beginning to take a more southerly route opening the route for Lp activity.

We have seen a few false dawn potential thunderstorm breakdowns already in the last few weeks. This might be another. Time will tell.

sryanbruen

Just because this came into conversation today with me and somebody, I thought I'd mention it here at the start of this post before I get into the models. I try to not let personal bias interfere with me when I do model outlooks. I only say what I think is likely to happen going by teleconnections, background signals and my methodology etc, or if something new appears in the models such as this Spanish plume then I discuss it too.

From each of the 12z runs today, they show a Spanish plume of some sorts by day 10 and the longer short range model, GFS, makes the pattern go into a cooler, unsettled phase after the Spanish plume. The Spanish plume on the GFS is quite dangerous heat and humidity which would make the atmosphere absolutely explode with thunderstorms. The ECM has the extreme heat further south and eastwards into France but still very warm nevertheless with a thundery low over us by day 10 which is Friday 13th July. In terms of the cooler, unsettled spell that the GFS is showing after the Spanish plume, let me post charts here that the model (specifically its 12z run on Wednesday 27th June last week) was showing for that kind of time frame (past day 10) for Saturday 7th and Monday 9th July. The model was showing that we were going to get into a very cool and unsettled phase with a northerly setting in even. Compare that to now of what's actually going to happen - a ridge from the Azores will become centred over top of the country delivering more warm/hot, sunny and dry conditions.

Models are progressive, they always underestimate the power of blocking. I remember back in February/March that they were bringing us into a milder spell of weather and low pressure from the south would completely knock out the blocking.

ECM clusters are 100% unsettled well out into the extended range but just over a week ago, the majority of them were also pointing towards very unsettled conditions for later this week onwards, see below.

Long range forecasts and models all point to a very dry (exceptionally so) and hot July such as the CFSv2, BCC etc. I have shown what the CFSv2 sees for July 2018 in the Summer 2018 discussion thread here: https://www.boards.ie/vbulletin/showpost.php?p=107410320&postcount=959

I know we're all in need of rain but I'm not going to sensationalise my weather forecast saying rubbish like "Summer is over, Atlantic onslaught on the way" etc. We should know the nature of these models by now after our years of looking at them especially since February, just look at the past week examples I gave you above. How about the thundery interlude that was supposed to occur the weekend just gone too?

The background signals also go in line with the long range models named.

To round it all off, ECM ensembles do not see Spanish plume at the moment. The mean at day 10 still has quite high pressure especially for an ensemble mean out that far which is incredible.

Farmer2017

So basically your saying that after 10 days the high is staying with little rainfall.

sryanbruen

Farmer2017 wrote: »

So basically your saying that after 10 days the high is staying with little rainfall.

A lot can happen in weather world in 10 days. The point of the FI chart thread here is to discuss the probabilities that something which is trending on the models past +120 hrs is likely to happen. The unsettled phase which the GFS model is picking up on could happen this time, it doesn't have to go the exact same way as last time. Maybe this time is different? You never really know. The smallest factor can throw a spanner in the works and mess everything up in the atmosphere to cause changes like a cyclone in oceans (such as typhoons in the Pacific or hurricanes in the Atlantic) can cause a ripple in the jet stream to make it go further southwards over the country and bring depressions (rain bearing weather systems) with it.

There have been times before when the minority were right (in this case, the minority are the unsettled ones) and the majority started to come in line with them closer to the reliable timeframe. At this point of time, the unsettled phase is out into the very unreliable timeframe on the GFS anyway.

So basically, a lot can happen in those 10 days to change the pattern. The smallest thing can do so whatever it pleases to. Just because the model was wrong last time doesn't mean it will this time. We will know it's wrong if continuous backdating and or downgrading occurs on the trend much like the thundery interlude that was supposed to come up from Biscay this Sunday and Monday just gone which was downgraded as the reliable timeframe came closer.

Hope that's understandable for you.

Meteorite58

The ECM showing very warm / hot out till the end of the run at T+240 by which time it is showing a lowering of geopotential heights but would still be warm, Showing the Iberian LP drift up under the UK and into France and showing the plume of hot humid air move more up through France and further into Europe. France would light up like a Christmas tree with severe thunderstorms I would imagine.

The ECM is showing a gradual flattening of the Atlantic ridge and showing weather arrive from the Atlantic out at +240. It is interesting that across the ocean atm The National Hurricane Centre is showing an area of disturbance a few hundred miles SE of Bermuda which is set to track Northward over the weekend and will possibly interact with a frontal system that I believe shows up on the charts moving in towards Ireland at the end of the run. This would possibly be just an area of LP / trough by this stage possibly carrying warm humid air and a good shot of rain ( other bands of rain behind it perhaps ? ). Lets see what comes of it.

hatrickpatrick

The 18z GFS is downgrading the Atlantic low somewhat at the end of the run, keeping the jet stream slightly more north than it was in the 12z:

12z:

gfs-0-384.png?12

18z:

Would still be an unsettled period, but it looks like the jet stream / Atlantic influence in the FI GFS is already being downgraded compared to the ongoing Azores / subtropical high influence.

sryanbruen

ECM clusters now going onto the more settled side. Yesterday's ECM 12z clusters completely got rid of the unsettled option at the extended and as well as keeping a big ridge over us as far out as day 10 (Friday 13th).

+240 hrs clusters (day 10)

+360 hrs clusters (day 15)

GFS 0z brings the Atlantic through after the Spanish plume with some quite deep depressions. In terms of the Spanish plume, it's a hot outlier in its ensembles.