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

Sammy2012 wrote: »

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

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

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.

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

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.

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.

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

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)

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 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 ,

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.

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!

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...

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 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.

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:




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.