LRF or attempting them

[johnholmes]

hi

I thought I should start a new thread as the other is very long.

As I posted a week or so ago the usual update for 168 hours on from the date of issue will be on a Friday evening with a quick update/comment the following Tuesday.

Verification will be attempted in a more organised manner than I've done so far with a date/time set for this which will enable us all to see how well or not the attempts are turning out.

Due to time constraints the issue today(Friday's) is done a bit differently so please let me know if you are unable to download it.

Update_Friday_9_May_2008_for_the_period_17_for_issue.doc

Edited May 10, 2008 by johnholmes

[J10]

Good Update John, and the format is fine for me.

[johnholmes]

tks Julian, hopefully anyone will be able to download it and it makes the job of inserting it into the web site a lot easier.

[PB22]

Thanks John, great stuff as always. I really am hoping winds don't go north of east, but it looks like it will be inevitable. This superb weather can't last forever sadly!

[damianslaw]

Yes your LRF seems a good call. A gradual cool down over the next few days but still mostly dry and sunny, nights may turn noticably cool especially in the north towards the end of next week.

The third week could well see cyclonic conditions but as you suggest it will be a flabby slow moving low pressure centred out to the west which will meander but eventualy get squeezed away by building high pressure again, where from uncertain at this stage.

[johnholmes]

Update for Tuesday 13 May for same period, as the issue of Friday 9 May for 17-25 May 2008

as usual there are a list of links at the end of this lrf

Lots to take into account so lets start with the AO and NAO

AO

this shows a rise then a fall and later another rise with increasing spread

As to be expected the NAO shows a similar pattern although not as pronounced

So some indication that blocking, to some degree, may be around for much of May, if this prediction of AO and NAO is correct.

How about the ENSO situation?

The chart below is a screen print of their latest idea so I hope you can read it.

Possibly some changes to occur some time down the line, maybe as we head into the first summer month?

How do NOAA view the model ouputs?

This is parts of their comments, the full version can be viewd here

http://www.cpc.noaa.gov/products/predictio...day/fxus06.html

and they are from Monday

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS ABOVE AVERAGE... 4 ON A SCALE OF 1 TO 5... DUE TO FAIR AGREEMENT AMONG THE MODELS AND FAIRLY GOOD AGREEMENT AMONG THE FORECAST TOOLS.

they do comment that a pattern change may be about to happen, currently pattern is

EVEN WITH THE MODEL/ENSEMBLE SPREAD...D+8 CHARTS ARE SIMILAR IN DEPICTING A RATHER STRONG MEAN TROF CENTERED NEAR 170W. TELECONNECTIONS RELATIVE TO THE CORRESPONDING NEGATIVE HGT ANOMALY CENTER FAVOR A MEAN RIDGE NEAR 140W AND A MEAN TROF JUST INLAND FROM THE WEST COAST.

Turning to the 500 mb charts that include the eastern Atlantic and into the European fringes.

the 8-14 day ensemble from today(Tuesday) for 21-27 May

This appears to suggest a flow from south of west into the UKwith a fairly long wave pattern in the 500mb flow. Long wave patterns tend not to change quickly, this in spite of that comment above from NOAA about a pattern change within the next 7 days or so – more conflicting evidence perhaps!

Their 500mb flow has had a hiccup with model problems so I am unable to show that for the past 3 days. Looking at the play through I have of the days prior to this problem suggests pretty similar really to what is above-hardly surprising. There are differences if you play the last few days of the ECMWF and GFS 500mb patterns.GFS is less keen, most of the time, on a flow from north of west than ECMWF.

So what of the update, does it need to be changed from this summary last Friday?

High pressure dominating the first part with the centre mostly to the north or north west giving temperatures below or near average over the country along with generally dry weather. This will be a change from the immediate future where its position has allowed warmer air to feed in either off the continent or from much further south at times. Rainfall should be mostly below average, after the onset over the following weekend(17-18) of a more northerly flow, and there will be a possibility of ground frost for northern areas at times. So a noticeable difference in temperature levels for a time. Later in the period the high pressure looks likely to give way to a more cyclonic type of airflow, but with no sign of any high winds. The 500mb trough becoming slow moving over or just west of the UK giving more unsettled conditions with rain or showers at times and with temperatures more normal or just above, this more especially for southern areas with the north still likely to see temperatures at or a little below the normal. This would be most likely if the 500mb trough with low pressure got to the east of the country for a short period.

I would amend it from where marked in red

I would now put, a spell of less settled weather but with the tendency for blocking north of the UK to return and for high pressure to once again take over. This will lead by the period end to mainly dry weather with temperature levels recovering to normal or above, especially in the south.

Next update will be Friday 16 May 2008

links

GFS usual

http://www.wetterzentrale.de/topkarten/fsavneur.html

from this it links to ECMWF and UK Met

NOAA links

comments on what is ussued by NOAA from CPC(climate Prediction Center)

http://www.cpc.noaa.gov/products/predictio...day/fxus06.html

synoptic review

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

500mb anomaly charts for days 8-14 in two charts

http://www.cpc.ncep.noaa.gov/products/pred...10day/500mb.php

prognostic discussion:-this explains how/why they think events may/may not occur along with % weightings for various models for temps/pressure/ppn etc

http://www.cpc.ncep.noaa.gov/products/pred...day/fxus06.html

this one talks of 30 day ideas Lan Nina etc

http://www.cpc.ncep.noaa.gov/products/pred...nge/fxus07.html

this is a list of contacts on the CPC team(04/03/08=not yet tried it?)

http://www.cpc.ncep.noaa.gov/information/p.../contacts.shtml

this is the actual circumpolar charts for various levels(use it for 200mb)

http://wxmaps.org/pix/hemi.00hr.html

ENSO etc-La Nina or El Nino, MJO(Madden Julian Cycle), Teleonnections, Blocking

http://www.cpc.ncep.noaa.gov/products/prec...JO/climwx.shtml

and another from NOAA

http://www.cpc.ncep.noaa.gov/products/prec...nnections.shtml

and another

http://www.arctic.noaa.gov/essay_bond.html

this covers

AO, NAO, PDO, NPI and much more

ECMWF/GFS/other links with Meteociel

Others

GP:- his latest link(14/05/08)or click on his name and trawl through his posts

http://www.netweather.tv/forum/index.php?a...sult_type=posts

Edited May 15, 2008 by johnholmes

[johnholmes]

No 4-Update on Friday 16 May 2008 for the period 25 May to 1st June 2008

For links which may help in reading this, abbreviations etc, please see the end of this update.

The check will be based on the 12z chart during the period 25 May-1 June

Average afternoon temperatures for this period are shown below (taken from data on the Met Office site).

From the Shetland Isles at around 13C to 17C for much of Scotland and Northern Ireland up to 19C over most of England and Wales, 20C for London

The cooler spell is already here for northern areas and will arrive in the south over the weekend. Probably lasting into Wednesday for many. Perhaps the most noticeable feature being ground frost even in some southern locations with vulnerable inland areas further north likely to experience an air frost. Mostly dry as well once the southern frontal zone has cleared away. I have yet to do a proper check but I suspect the cool spell was fairly well indicated although with doubts about just where the high would settle when the forecast was issued on 9 May.

So to the next period.

The AO and NAO are both predicted to show an overall rise in values, (rising then falling then rising again). The PNA is predicted to rise slightly then fall again. La Nina is as the last update. Effects around the equatorial zone suggest another westward movement of tropical convection with its effect on the PNA initially to be +ve but later it could return –ve.

On the daily ECMWF and GFS 500mb anomaly charts there continues to be a difference much of the time as to where they put the mainly +ve and –ve areas. GFS tends to favour a flow from south of west whilst ECMWF seems to me to oscillate between a similar flow and one west of north. See the one this morning below. Both do suggest a +ve area over/west of the UK. The crux being just where any trough and ridge might lie.

GP has recently commented that GFS, IF the pattern being suggested by events outside the North Atlantic occurs, has a tendency to be at a bit of a loss to know how to deal with disrupting Atlantic troughs, a possibility if the above comments turn out to be correct.

In the checks I'm currently running on the GFS 4x issues each day there is a continuing variability between, not just one run and the next, but between runs for the same time on subsequent days. This was a feature of the last check with it being well into the T+384 period before useful guidance from GFS became clear. Currently for 29 May it has run about 4 different scenarios, varying from ridging from the south west to a low over/west/north west of the UK!

Inputs from NOAA

The 24-30 May 500mb anomaly chart shows +ve from north east of the Uk down towards Iberia, only a small amount, with the +ve also north then west of Greenland into the north east of N America. It seems to suggest the 500mb ridge will be east of the UK.

They are still not too happy (for their area) at the models consistency and rate them only 2 out of 5 for the whole period 6-14 days (out to 30 May)

Summing up this period then I would suggest the following.

An increase in temperatures from mid next week due to high pressure again taking over as the dominant factor but then it tending to drift to the north east as an upper trough is driven across the Atlantic, thanks to the wave length between the west of the States and Europe. Temperatures recovering through the week as we head towards the BH weekend. Will it last? Probably not, although there are conflicting signals as to how it may break down. A warm rather unsettled perhaps thundery breakdown or a cooler easterly type with the high to the north east and the lows running more or less east not north east.

Beyond that, out towards the start of official summer, and high pressure is likely to take over again still over Scandinavia although it is possible for it to move further west. If it stays to our north east then parts of the north west could see the best weather as areas over/east of high ground have a coolish flow from the east, with its attendant cloud at times.

Interestingly(this is my first use of it) our own NW LRF suggests a large +ve pressure anomaly for June to the north east/east north east as opposed to its forecast for May which showed the +ve anomaly in the Greenland area.

A shortish update on this next Tuesday (20 May) with a new full update next Friday 23 May for a further week ahead (into the first week of June)

List of links for LRF work

http://www.wetterzentrale.de/topkarten/fsavneur.html

from this it links to ECMWF and UK Met

NOAA links

comments on what is issued by NOAA from CPC(climate Prediction Center)

http://www.cpc.noaa.gov/products/predictio...day/fxus06.html

synoptic review

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

500mb anomaly charts for days 8-14 in two charts

http://www.cpc.ncep.noaa.gov/products/pred...10day/500mb.php

prognostic discussion:-this explains how/why they think events may/may not occur along with % weightings for various models for temps/pressure/ppn etc

http://www.cpc.ncep.noaa.gov/products/pred...day/fxus06.html

this one talks of 30 day ideas Lan Nina etc

http://www.cpc.ncep.noaa.gov/products/pred...nge/fxus07.html

this is a list of contacts on the CPC team(04/03/08=not yet tried it?)

http://www.cpc.ncep.noaa.gov/information/p.../contacts.shtml

this is the actual circumpolar charts for various levels(use it for 200mb)

http://wxmaps.org/pix/hemi.00hr.html

ENSO etc-La Nina or El Nino, MJO(Madden Julian Cycle), Teleconnections, Blocking

http://www.cpc.ncep.noaa.gov/products/prec...JO/climwx.shtml

and another from NOAA

http://www.cpc.ncep.noaa.gov/products/prec...nnections.shtml

and another

http://www.arctic.noaa.gov/essay_bond.html

this covers

AO, NAO, PDO, NPI and much more

ECMWF/GFS/other links with Meteociel

links to definitions of some of the terms used

AO=

http://booty.org.uk/booty.weather/FAQ/AF.h...cticOscillation

NAO=

http://booty.org.uk/booty.weather/FAQ/2B.htm#2B.10

MJO=

http://www.cpc.ncep.noaa.gov/products/prec...k/MJO/mjo.shtml

EL Nino/La Nina=

http://booty.org.uk/booty.weather/metinfo/ENSO_ref.htm

http://www.pmel.noaa.gov/tao/elnino/la-nina-story.html

also this=

http://www.pmel.noaa.gov/tao/elnino/wwv/

more reading here

http://www.cru.uea.ac.uk/tiempo/floor2/data/soi.htm

Edited June 1, 2008 by johnholmes

[johnholmes]

No 5-Update for Tuesday for the period 25 May to 1st June 2008

a brief one only

Average afternoon temperatures for this period are shown below (taken from data on the Met Office site).

From the Shetland Isles at around 13C to 17C for much of Scotland and Northern Ireland up to 19C over most of England and Wales, 20C for London

AO and NAO are still, for the most part, around or showing –ve.

NOAA are suggesting the flow over their area will be 'highly amplified' is their comment for the end of May.

This suggests the wavelength across the Atlantic will tend to be somewhat similar. Thus the key will be where the downwind trough and ridge at 500mb settle. I suspect the trough will be west of the UK for much of the period, after the BH weekend as this lrf starts on the Sunday. This would go along more with the ECMWF charts for the end of May than the GFS charts. Setting up a surface high to the north east of the UK which will be the dominant factor after the BH weekend as the low slides away with the 500mb trough re positioning west of the UK. There is also a high Azores cell off to the south west with a 500mb trough lurking! This would give a fairly settled and mainly dry start to June. Temperatures away from east coast districts rising again to a little above normal values, possibly into the rather warm category. No strong winds either.

This is perhaps rather less certain that the main update last Friday. There are increasing signs of a 500mb trough for the far north tending to split the two ridges, one in the Atlantic and one north east of the UK. Its finely balanced at the moment. On the fence some of you will say, so be it. I find it not sensible to pretend I can predict one way or the other when I can't.

The check will be done sometime in the period 25 May-1 June.

The next full update will be on Friday 30 May out to 8 June

Various links are shown in the full update done last Friday

http://www.netweather.tv/forum/index.php?s...p;#entry1255198

Edited June 1, 2008 by johnholmes

[Jack Wales]

This is perhaps rather less certain that the main update last Friday. There are increasing signs of a 500mb trough for the far north tending to split the two ridges, one in the Atlantic and one north east of the UK. Its finely balanced at the moment. On the fence some of you will say, so be it. I find it not sensible to pretend I can predict one way or the other when I can't.

Various links are shown in the full update done last Friday

http://www.netweather.tv/forum/index.php?s...p;#entry1255198

Good post John, I enjoy reading these, especially as they have been very accurate.

The area of your post I've highlighted is what I believe to be key going into June. If the ridge is split into two, this could give rise to LP hitting us from the WNW. I think BFTP mentioned this in another thread as being a synoptic that would take time to unlock itself. Although I believe the signs are there for a strong Azores high to form, in this instance it could take on a NW to SE formation. It's still early days though and by the weekend we should have a better idea as to how this will play out.

[johnholmes]

rather than start another thread showing the checks on lrf output I'll drop them into my blog which you will find at the link below

http://www.netweather.tv/forum/index.php?s...c=47611&hl=

[johnholmes]

6-lrf update issued Friday 23 may for the period out to 8 June

average temperatures for the beginning of June, extracted from Met O data suggests:-

12-13C for the N Isles to 17C or so for much of Scotland and N Ireland up to 18-19C for most of England and Wales(20C for London)

Nothing changes with mixed signals from the different sources continuing.

Before I go into the main part of the lrf just to focus on the immediate shorter term from the end of this weekend.

Its one of the biggest turn arounds I've seen since close model watching of GFS over 3-4 years. I've been focusing on my next model checks which is for 29 May and there have been marked changes in the main players, ridges and troughs since I started it. Quite why the model is having such a difficult time I cannot say. Perhaps(?) it is something to do with two of the major links, the AO and NAO, both showing the largest swing in the past 3-4 months, both upwards.

Most of the sources I'm using to try and predict temperatures, dryness/wetness etc, for the period of this lrf are showing a continuing trend for low contour heights over the pole. This allied to high contour values(relative to averages) in the region of east of Greenland into Europe, sometimes Scandinavia. With a second lower area in mid Atlantic(the Azores high).

The AO is below and the NAO below that.

The latest 500 mb anomaly charts for 500mb from ECMWF and GFS are shown below. They do mostly indicate what I've commented on above regarding the low and high contour values relative to the average.

NOAA have shown a degree of belief, higher than for some time, in the overall upper air pattern with ECMWF and to a lesser extent GFS and others for the period well into next week. Allocating a mark of 4 out a possible 5 this morning. This has been a feature of their comments over the past few days.

Their own version of 500mb anomaly charts for the first part of this lrf is shown below; for the period out to 5 June. Still a 500mb trough in the UK area with a flow probably from just north of west seeming likely. Its difficult to be certain but the wave length does suggest that it will not change very much POSSIBLY the trough edging a shade further west with high pressure then trying to build again somewhere to the north with a POSSIBLE link to the Azores high. All rather problematical. It is even possible that something which is difficult to see on that chart, out over Europe, may become a player – the Euro high? It does seem to suggest that pressure values would tend to be lower over Iberia than mainland Europe.

So to an attempt at a LRF for the period shown.

LRF Summary to 8 June

Once the BH weekend is out of the way it will take a while for the atmosphere to settle down again, so probably much of the week on the unsettled side with temperatures around or above normal, well above for some southern and central areas, along with hefty showers for some.

By about the following weekend I suspect that a 500mb trough will affect the northern half of the country, with some rain or showers around for many, especially the further north and west in the country you are. This could also trigger some showery outbreaks further south.

Thereafter the upper ridge will begin to take over with a period of mainly dry and settled weather and rising temperatures again from values which will have fallen to or just a touch below with the unsettled weather. This though affecting chiefly the northern half with some parts of the south staying around or even above normal through the period. This latter spell into June should give mainly dry weather. Some central and southern parts may become very warm at times. Current indications are that the ridge may arrive from somewhere to the north. As to east or west that is not clear at the moment. It may again be a mix of the Azores high and ridging into Europe or Scandinavia..

The next full update will be Friday 30 May with a short update on Tuesday 27 May.

This lrf will have a validation check for the weekend of 1-2 and again 7-8 June

[azores92]

6-lrf update issued Friday 23 may for the period out to 8 June

average temperatures for the beginning of June, extracted from Met O data suggests:-

12-13C for the N Isles to 17C or so for much of Scotland and N Ireland up to 18-19C for most of England and Wales(20C for London)

Nothing changes with mixed signals from the different sources continuing.

Before I go into the main part of the lrf just to focus on the immediate shorter term from the end of this weekend.

Its one of the biggest turn arounds I've seen since close model watching of GFS over 3-4 years. I've been focusing on my next model checks which is for 29 May and there have been marked changes in the main players, ridges and troughs since I started it. Quite why the model is having such a difficult time I cannot say. Perhaps(?) it is something to do with two of the major links, the AO and NAO, both showing the largest swing in the past 3-4 months, both upwards.

Most of the sources I'm using to try and predict temperatures, dryness/wetness etc, for the period of this lrf are showing a continuing trend for low contour heights over the pole. This allied to high contour values(relative to averages) in the region of east of Greenland into Europe, sometimes Scandinavia. With a second lower area in mid Atlantic(the Azores high).

The AO is below and the NAO below that.

The latest 500 mb anomaly charts for 500mb from ECMWF and GFS are shown below. They do mostly indicate what I've commented on above regarding the low and high contour values relative to the average.

NOAA have shown a degree of belief, higher than for some time, in the overall upper air pattern with ECMWF and to a lesser extent GFS and others for the period well into next week. Allocating a mark of 4 out a possible 5 this morning. This has been a feature of their comments over the past few days.

Their own version of 500mb anomaly charts for the first part of this lrf is shown below; for the period out to 5 June. Still a 500mb trough in the UK area with a flow probably from just north of west seeming likely. Its difficult to be certain but the wave length does suggest that it will not change very much POSSIBLY the trough edging a shade further west with high pressure then trying to build again somewhere to the north with a POSSIBLE link to the Azores high. All rather problematical. It is even possible that something which is difficult to see on that chart, out over Europe, may become a player – the Euro high? It does seem to suggest that pressure values would tend to be lower over Iberia than mainland Europe.

So to an attempt at a LRF for the period shown.

LRF Summary to 8 June

Once the BH weekend is out of the way it will take a while for the atmosphere to settle down again, so probably much of the week on the unsettled side with temperatures around or above normal, well above for some southern and central areas, along with hefty showers for some.

By about the following weekend I suspect that a 500mb trough will affect the northern half of the country, with some rain or showers around for many, especially the further north and west in the country you are. This could also trigger some showery outbreaks further south.

Thereafter the upper ridge will begin to take over with a period of mainly dry and settled weather and rising temperatures again from values which will have fallen to or just a touch below with the unsettled weather. This though affecting chiefly the northern half with some parts of the south staying around or even above normal through the period. This latter spell into June should give mainly dry weather. Some central and southern parts may become very warm at times. Current indications are that the ridge may arrive from somewhere to the north. As to east or west that is not clear at the moment. It may again be a mix of the Azores high and ridging into Europe or Scandinavia..

The next full update will be Friday 30 May with a short update on Tuesday 27 May.

This lrf will have a validation check for the weekend of 1-2 and again 7-8 June

very optimistic, but we shall have to see if you're right.... i hope so, because i dont want a prolonged unsettled period, but it is still a possibility....

[mcweather]

Thank you for all your all hard work again John. Your forecasts are always backed up with good detail from the models even when the models differ from one another. I particularly like the way you explain why they differ sometimes and your hunches are very often on the right side of things. My interest has always be in looking beyond the next five days so I always find your forecasts very interesting. Although I am interested in all types of weather, like many on here I am a cold and snow fan at heart, so I look forward to the day when your forecast takes us into the start of the next 47, 63 or 79.

In the meantime I hope the warming up bit of your current lrf comes off because I work outdoors and really don,t want to get into summer as ghastly as last years.

[johnholmes]

thanks MC, its a learning curve for me through the back end of this winter, now heading into the summer, and again new territory; as to next winter, well I am looking forward to seeing how accurate I can get about 3 weeks ahead.

But no 1947 or 1963 I hope as I've often said before. I remember them both - no thank you. 5-6 days of it say twice a winter okay, months of it yuk

[johnholmes]

No 7-Update Tuesday 27 May for period out to 8 June

average temperatures for the beginning of June, extracted from Met O data suggests:-

12-13C for the N Isles to 17C or so for much of Scotland and N Ireland up to 18-19C for most of England and Wales(20C for London)

If anything I am less certain of what to write in this than any previous lrf!

Looking at the most used model GFS, it has chopped and changed so much in the short time scale, from a dry warm BH to the version which many in the south actually got and is no more settled in the longer term. The T+384 check I'm currently assessing, based on 29 May, has had 3 major changes in it. ECMWF seems to be the preferred model with NOAA for their area but that has also done some changing in the time scale I'm interested in. In the last lrf I mused over the problems the models seemed to be having as perhaps being linked to the major change being suggested in both AO and NAO which in turn probably stem from events even further afield. ENSO output is suggesting that La Nina will become almost neutral during the summer and other data also is showing a change. Not having looked at this type of forecasting before it may be that this kind of step change usually occurs at this time of the year. It is after all the major change of season for the hemispheres, one into summer the other into winter. It sure does make for head scratching in trying to decide what is a reasonable forecast for the period shown.

Looking first at the output of ECMWF and GFS 500mb anomaly charts over the past few days. They are fairly consistent if you look at the past week in that they well predicted the higher pressure to the north and west south west along with low pressure to the south of the country. Their prediction for 6 June(Friday) is shown below. This has +ve anomalies(with both models) to the north east and out in the Atlantic south of 50N. The main –ve anomalies are to the north west(more so with ECMWF) and a smaller one(this time chiefly GFS) in the Iberia area. Translating to the surface this would suggest, to me, that by that time(Friday 6 June) we could expect high pressure to our north east and well out in the Atlantic with perhaps a cut off low, or at least a marked trough, in the Iberia area and with a low somewhere near/west of Iceland? This is not that far off from what the 240 charts, over the past few days, including the 00z from GFS and ECMWF have been suggesting, see the NW version below; ECMWF on the left and GFS on the right. Neither would lead one to expect totally settled weather, especially ECMWF. But neither suggests the temperatures would be below normal.

There seems little doubt that the 500mb trough will be west of or possibly almost over the UK. So a spell of settled weather seems a lower probability than unsettled, but with temperature levels not below normal for most for most of the time. Possibly even well above normal in places, chiefly in the south, depending on just where any high settles. No sign of any strong winds.

So this would give a different version of weather, trough dominated rather than ridge dominated compared to the issue last Friday. This is probably the case even if the high develops more over Europe/Scandinavia than I've suggested. In that case, very warm for the southern half at least but possibly rather thundery. Thus the overall idea of an unsettled spell but above average temperatures seems a reasonable punt this evening.

We shall have to wait and see which idea was nearer the actual?

As to what happens further into June then we can start to think about that now for the next main update on Friday 30 May.

Edited June 1, 2008 by johnholmes

[johnholmes]

I'm going to post the update this evening in two ways. First is the text only for those with slow download speeds and second will be a link that includes the charts, 7 of them this evening.

The text only

No 8-Update on Friday 30 May for period to 8- 15 June

Verification will be 8 June and 15 June

average temperatures for this period are

the beginning of June, extracted from Met O data suggests:-

12-13C for the N Isles to 17C or so for much of Scotland and N Ireland up to 18-19C for most of England and Wales(20C for London)

I seem to be posting this each time recently, but its certainly not an easy choice with once again different outputs suggesting differing outcomes for this period. If GFS and ECMWF are to be believed then the first part would appear to be a cool spell with surface high pressure to the north or north west of the Uk and low pressure along with a 500mb trough over or near the UK and a flow north of west at the surface.

Anyway let us have a look in rather more detail.

What is happening in the tropics belt is not that different from what was occurring in late March or late April(see old charts or the post by GP here(http://www.netweather.tv/forum/index.php?a...sult_type=posts). This gave relatively low pressure over areas of the north east Atlantic see below with a chart from NW chart archives and by 30 April this 500 trough and attendant surface low were right over the Uk with a surface high to the west from Greenland well down into the Atlantic. By the end of the first week much of the country was basking in well above normal temperatures for early May, the start of a prolonged dry period as well. I'm not suggesting this is going to repeat itself just yet!

Looking into what may happen in the next few weeks in this area ,(an important guide quite often to subsequent weather patterns in the North Atlantic is the signal coming out of the tropics), and I have to confess this is very new territory to me and again for a better view on this from GP then read his link just quoted.

It does seem to me to offer a rather different outcome to what I mentioned in the paragraph above regarding GFS and ECMWF. However even GFS only goes out to 15 June in its farthest FI with ECMWF no further than 9 June. So some of the probabilities stemming from what is expected to happen in the tropics are unlikely to be really being taken on board by the models just yet.

Turning to other teleconnections or events that impact on our area, La Nina, AO and NAO (for explanations of some of the terms you will see used in these forecasts please refer to the links at the end of this lrf).

La Nina, at the last update from NOAA on 27 May has this to say,

'

La Niña is present across the tropical Pacific Ocean.

•Equatorial SSTs in the Pacific Ocean remain below average from west of the Date Line eastward to 120ºW, but negative departures have weakened considerably since mid-February 2008.

•The patterns of tropical convection and equatorial winds continue to reflect La Niña.

•Recent equatorial Pacific SST trends and model forecasts indicate that ENSO-neutral conditions will likely develop during June-August 2008.'

and the link to the full 30 page(!) report is below

http://www.cpc.ncep.noaa.gov/products/anal...s-fcsts-web.pdf

The AO showed this yesterday

The NAO

This has a substantial fall predicted followed by a rise towards neutral later

Is this the cause of the models showing a surface high west of north from the British Isles?

ENSO is predicted to tend to a neutral value. What does that mean in relation to the anticipated weather type in our area? Again I turn to GP for help with this. He suggests and I quote his pm to my query in full,

'By definition, ENSO neutral conditions suggest no SSTA anomalies across the Equatorial Pacific and so we would logically assume no overall signal.

However, 'neutral' does capture SST anomalies < +/- 0.5 C. It may not reflect 'atmospheric memory' of previous Nino or Nina so I would look at previous examples of a fading Nina going into the Summer. That stated, SSTA will dip back into weak Nina status c/o the easterly trades in place over the last week.

As ever, the current situation looks highly related to what is going on over the tropical Pacific and Indian Oceans. Recent supression of tropical convection has lead to a strong easterly component to the atmospheric flow, resulting in global momentum falling sharply and reflected in a negative projection of the Global Wind Oscillation:

http://www.cdc.noaa.gov/map/images/gcm/gwo_90d.gif

If we look at the past two episodes when the GWO was in phases 2/3, we get a big -ve H500 anomaly over the UK. However, convection is inceasing over the Indian Ocean and a westerly flux is inevitable in the next 7-10 days driving the GWO through phase 4 and perhaps even briefly into Phase 5 (net global westerlies). I think if we are looking for fine summer weather, some westerly component to the atmosphere is a prerequisite.'

This is not a cop out from me I genuinely do not yet understand some of the teleconnections sufficiently well enough to pretend and give a forecast on it. So thanks GP.

What do NOAA have to say in the nearer term about the models?

This is their comment this morning

'TELECONNECTIONS WITH A NEGATIVE ANOMALY OVER NUNAVUT AND A POSITIVE ANOMALY MOVING ACROSS THE EASTERN PACIFIC FAVOR TROUGHING NEAR THE WEST COAST INITIALLY BEFORE THE TROUGH PROGRESSES TOWARDS THE GREAT BASIN EAST OF THE MOBILE PACIFIC POSITIVE ANOMALY/BROAD

RIDGE. A BUILDING POSITIVE ANOMALY OVER GREENLAND SHOULD ALLOW FOR A PROGRESSIVE CLOSED CYCLONE UNDER ITS BASE NEAR THE 50TH PARALLEL IN THE ATLANTIC. THE MODELS AGREE ON THESE IDEAS.'

So it would seem, out to just be fore the start of this forecast that we should be looking at what they suggest as the start point. Okay so what does GFS/ECMWF have for 6 June? For some reason GFS in NW is not showing as I type this so the basic Wetter charts are shown

GFS on the left and ECMWF on the right; both for 12z

Well there are similarities; the 500mb trough but they differ in positioning surface highs and lows relative to the trough. But the main factor is the 500mb trough, its in about the right position and supports the NOAA forecast comments above. At 240 hours its already a long way ahead to expect the surface features to be very good.

Now to have a look at the NOAA 500mb anomaly charts, no ensemble charts are available and have not been for some time due to their computer problems

4-8 June on the left=5 and 6-12 June on the right=6

Both have –ve to the west of the UK and +ve to the north east/north and across to the Greenland area. As often happens the further out the time scale the less the anomaly is shown as. (This is not necessarily borne out by subsequent actual charts). In each case the 500mb flow is shown as a trough immediately over the western side of the country and into Iberia.

Without making any decision yet I wonder what the GFS chart (the link to the NW version is here and was the 06z when I typed this) http://www.netweather.tv/index.cgi?action=nwdc;sess=

At T+264 it had a very well developed surface low from near Newfoundland all the way to the area between Iceland and Scotland. To the north of that, high pressure in a belt from north of Norway across Greenland into north east Canada. Another area of low pressure was seen over Iberia (the more or less classic 'heat' low of summer months in that area). So not too far from what I suggested from the NOAA anomaly charts above. If we move the time scale on to further into FI then GFS goes a bundle on the idea the main low pressure transferring ene to northern Norway and the Azores ridge building north(winter memories!). Is this real is the question given some opposing ideas from other data?

Finally a look at the GFS-ECMWF 500mb ensemble comparisons for 9 June=7

Initially it looks like chalk and cheese in the vicinity of the UK. One has a flow just south of west with a fairly large –ve anomaly (GFS-so no surprise there) with +ve anomalies over Greenland. EMWF prefers +ve anomalies north and north east of the UK with a smaller one to the west giving a cut off high to the east and a deepish 500mb low over Iberia. Playing back the past week or so to see how the pattern has evolved and they have both not really shown great consistency. If anything the last couple of charts from GFS seem just a bit more logical in sequence (although ECMWF was not available yesterday so that may be a little unfair on it).

So to a prediction taking us through from about 7/8 June out to 15 June.

We are in a run of somewhat unsettled but rather above average temperatures for many. This seems set to continue into the first part of this period.

I would think that pressure will be relatively high in a belt from north east round to north west and low to the south(Iberia area) and also with a 500mb trough which will be west of the UK much of the time. Thanks to features well upwind, and some of the teleconnections, this trough will move both east and west through this whole period. Initially I expect it fairly well to the west with probably some kind of surface low, possibly with a 500mb cut off, near/over Iberia. The net result will be for warmish southerly winds for a time but with the likelihood of showery outbreaks, especially during the afternoons and evenings, with daytime heating and the moisture levels aiding this. Fairly light winds generally and possibly some low cloud near eastern coasts from time to time.

Further into the period and its even less clear. There are signs of the Arctic vortex moving east and the higher pressure over Scandinavia edging west coupled with the area of low pressure in the Atlantic. This could lead to the scenario GFS keeps trying to hint at, that is a cooler flow from north of west. This would tend to fit, to some extent, with the idea of the NAO going –ve again, although the other teleconnections may be pointing to a more westerly flow.

For the moment I think it sensible to leave it with those two options just mentioned and wait for the short update next Tuesday 3 June to see if its any clearer.

References and links

GFS usual

http://www.wetterzentrale.de/topkarten/fsavneur.html

from this it links to ECMWF and UK Met

NOAA links

comments on what is issued by NOAA from CPC (climate Prediction Center)

http://www.cpc.noaa.gov/products/predictio...day/fxus06.html

synoptic review

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

500mb anomaly charts for days 8-14 in two charts

http://www.cpc.ncep.noaa.gov/products/pred...10day/500mb.php

prognostic discussion:-this explains how/why they think events may/may not occur along with % weightings for various models for temps/pressure/ppn etc

http://www.cpc.ncep.noaa.gov/products/pred...day/fxus06.html

this one talks of 30 day ideas La Nina etc

http://www.cpc.ncep.noaa.gov/products/pred...nge/fxus07.html

this is a list of contacts on the CPC team (04/03/08=not yet tried it?)

http://www.cpc.ncep.noaa.gov/information/p.../contacts.shtml

this is the actual circumpolar charts for various levels (use it for 200mb)

http://wxmaps.org/pix/hemi.00hr.html

ENSO etc-La Nina or El Nino, MJO (Madden Julian Cycle), Teleconnections, Blocking

http://www.cpc.ncep.noaa.gov/products/prec...JO/climwx.shtml

and another from NOAA

http://www.cpc.ncep.noaa.gov/products/prec...nnections.shtml

and another

http://www.arctic.noaa.gov/essay_bond.html

this covers

AO, NAO, PDO, NPI and much more

ECMWF/GFS/other links with Meteociel

the explanations link has recently been changed so I will post up a new one when I get the time. In the meantime please try these links

The NOAA data includes comments on most of the most bandied around acronyms, AO, NAO, MJO, El Nino, La Nina etc and an explanation of most of these can be found below.

If you lose this list then go here

http://www.netweather.tv/forum/index.php?showtopic=46150

and they will be there all the time to bookmark or make your own list from them.

AO=

http://booty.org.uk/booty.weather/FAQ/AF.h...cticOscillation

NAO=

http://booty.org.uk/booty.weather/FAQ/2B.htm#2B.10

MJO=

http://www.cpc.ncep.noaa.gov/products/prec...k/MJO/mjo.shtml

EL Nino/La Nina=

http://booty.org.uk/booty.weather/metinfo/ENSO_ref.htm

http://www.pmel.noaa.gov/tao/elnino/la-nina-story.html

also this=

http://www.pmel.noaa.gov/tao/elnino/wwv/

more reading here

http://www.cru.uea.ac.uk/tiempo/floor2/data/soi.htm

or

http://booty.org.uk/booty.weather/FAQ/2B.htm#2B.12

and more!

http://www.pmel.noaa.gov/tao/elnino/nino-home.html

text and charts following but its a very large file so may take a while to download.

Update_on_Friday_30_May_for_period_to_15_june_with_charts.doc

Edited June 1, 2008 by johnholmes

[johnholmes]

No 9 - Update on Tuesday 3 June for 8-15 June

A short update this evening with a full update for another week ahead on Friday

For links about terms used and for average temperatures for the country please see update no 8 above this post.

Most outputs from various sources are giving more grounds for believing, once this spell is out of the way, that most of the period right from next weekend is going to be dominated by high pressure. They also appear to me to give a better idea than last Friday on where that surface high may settle.

Events around the tropics, north and south hemispheres, along with ideas on QBO, ENSO, AO and NAO all seem to point to that idea.

What is still difficult though is deciding where that surface ridge may try to put down roots. The major players, on the synoptic front, are, as always, the long wave troughs and ridges. The pattern looks to be setting up for a trough to be around mid Atlantic(at 500mb) with a trough at the surface, with lows from time to time tracking from south of Greenland into the Iceland region. This would fit with a ridge of sorts (500mb) over the European/Scandinavia region. With the AO and NAO looking to go +ve, at least for a time, then that would suggest that the surface high should be somewhere south of 60N, probably around 50N and east of the UK. Both these would tend to give a spell of mainly dry weather for many and with temperatures, especially over southern districts above, perhaps well above at times, normal. In the far north then a little less settled as the 500mb trough swings east from time to time with their associated surface lows, although warming out each time as it does so. Fairly light winds away from the far north and even here no signs of any gales.

That said, the position of the high is still not certain. I would rate the prospect of it being in the position suggested as about 70-80%. There is still the possibility, 20-30% of it setting up shop west north west of the UK. IF that happened then more settled in the far north but cooler for sure over the southern half.

As to further ahead, beyond 15 June, then Friday may allow us to peep that far. Initial ideas seem to point to PERHAPS some change in pattern as the AO and NAO are forecast, again, to go –ve but we wait and see what the various outputs suggest before then.

Edited June 6, 2008 by johnholmes

[johnholmes]

No 10 can be viewd at the link below

Its got text and charts together as its taken quite some time to put together and its rather late to be posting a lot of charts into script here, so I hope it downloads for anyone wanting to read it.

No_10_text_images_issued_6_june.doc

[johnholmes]

11-Update Tuesday 10 June for the period 15-22 June

Links to various sites are in the last main update No 10

Average Maximum temperatures for this period, beginning the 3rd week in June are:-

13C in Shetland to 18C for much of Northern Ireland and Scotland to around 20C for England and Wales, with 21C for the London area.

The usual short version for a Tuesday.

The basic input from NOAA and the GFS along with the 500mb anomaly charts all support the idea of a surface flow north of west into the UK and an unsettled look to it.

The 500mb flow seems set to be a trough off the eastern seaboard of America by about 18/19 June with a subsequent ridge to its east and downwind from that a trough, much as the ECMWF and GFS show on the chart for 20 June. Looking at the wavelength I would expect those positions to move east although fairly slowly. This would give a ridge over the UK area I would estimate some 4-6 days later. Now how that 500mb ridge changes/develops in that time is open to various ideas! Will it become a cut off upper ridge or, will it be north of or south of 50N. I have no idea at the moment although the NAO staying near or just below zero, to me, suggests it may revert to somewhere north of 50N, but where? The NOAA output, does seem to suggest north of and well west of the UK/50N. Also La Nina is expected to become neutral or rather ENSO is expected to. This again tends, to me, to suggest high pressure north of 50N and west of the UK, possibly towards the Greenland/Iceland area. It may try to link with the Azores high. I’m unable to give much idea at the moment.

So a summary is

On the cool and unsettled side to start this period with prospects for it settling down with the direct northerly being cut off. So later more settled and with temperatures slowly rising to above normal, especially in the south. Most places becoming generally dry and winds mostly not above moderate once the northerly has been cut off.

This will be validated on 15 and 22 June

[johnholmes]

No 12 Update on Friday 13 June From 22-29 June

Almost through the first month of summer by the end of this lrf and not really all that summery so far, so what about this period?

Average temperatures for the end of June are

14+ for the N Isles to 18+ for Scotland and N Ireland, mostly 20+ for England and Wales with London on 21+.

The usual links are shown at the bottom

From our current run of below average temperatures with the flow from the north and showers for some, especially on any troughs or areas exposed to the flow, is there going to be much change?

The current unsettled weather, dominated by a 500mb trough that keeps re aligning near the UK with surface blocking, beneath a 500mb ridge, in the Greenland area, seems likely to continue into almost the start of this period. Just a probability of the set up changing sufficiently for the surface flow to be from the south rather than a northerly point by then, although remaining generally unsettled.

Let us take a look at the teleconnections causing this and their probable influence through the period in question.

Enso will remain in a neutral phase for the summer period is the latest update from NOAA.

They also show that the AO is currently well below the zero line as is the NAO. Both are predicted to rise but remaining, for the most part, below the zero line. This usually suggests that surface high pressure is often in evidence well north of 50N. Its position critical, as it is in the winter, as to the flow the UK gets.

Other NOAA data: their 500mb anomaly charts, that a major +ve area is expected to be in the area of 60N and 60-80W. This ties in with a prediction (with a high agreement of 4 out of a score of 5) for major troughs to be upwind around 140W with another less marked one 80-90W. The next trough downwind from the 60-80W ridge is anywhere between 20W and 20E. This has been a feature of the weather over the UK area for a good many days. The 500mb trough oscillating almost east-west as relatively short wave troughs move through the longer major troughs and ridges. Nothing seems likely to change, in my view, on any major scale in this time period.

Turning to the mix of ECMWF and GFS 500mb anomaly charts (and NOAA currently, out to about T+168, suggest a mix of, quoting,

DERIVED BLEND FOR DAYS 5-7 IS 60/40 ECMWF/GFS ENS MEAN

With once again ECMWF being favoured over their own GFS output. A fairly regular occurrence and one which our Storm chasers seemed to support with their comments about which model gave the best short range upper air guidance.

The latest chart from ECMWF and GFS, and they have, as they have over the past week, got similarities but also differences. Both seem feasible when comparing their changes with the previous model run over the past 7 days. The indications would suggest that it's a westerly flow, possibly north of west with a marked trough over/east of the UK on ECMWF (by 23 June) with GFS favouring the trough west of the UK. So which is going to be right? Each would give rather different conditions in that time period.

Overall I think that the ECMWF is probably the better bet at that range (the start of the period). Beyond that and its even more of a difficult choice. I'm unsure looking at the last week's data on these two outputs I am unable to give a weighting more to one than the other. I suspect we may have a more north of west flow than a south of west pattern for most of the period, possibly just short term flows south of west as depressions run east north east.

To sum up the weather for this period

No sign of any real warmth, other than around and occasionally above normal for southern and south eastern areas of the country. Generally a rather unsettled period with rain or showers at about or a bit above normal and temperature levels, much of the time, either at or below the late June average. Possibly a fair bit below at times. No serious winds but quite breezy for the north west quarter of the country as low pressure pass close to that area from time to time. The south east of the country doing best for less rainfall and temperatures above normal at times.

Looking right to the end of the month and it seems fairly evenly poised to me, perhaps 60/40 in favour of cooler rather than warmer than average.

Next update will be Tuesday 17 June and the verification will be done for 22 and 29 June.

if anyone wants to wade through my ramblings with the data I've played around with since update no 11 try this link

12_Update_on_Friday_13_June.doc

Edited June 13, 2008 by johnholmes

[pottyprof]

Thanks for this John. Interesting thinking mate..

[johnholmes]

No 13-Update Tuesday 17 June:-22-29June

Usual shortish update this evening with a fuller one and for a further week ahead on Friday.

The latest teleconnections have now gone for a rise in both AO and NAO through into the beginning of July. This is a different idea to previous runs. I am no expert on these but I wonder if their accuracy is any greater than any other forecasting tool? For instance the NAO issued for 16 June showed a fairly strong indication of it becoming positive (certainly some spread but the majority showed positive). But its remained just about on the zero line up to 16 June! I suspect like most other forecast tools some caution needs to be used unless there is overwhelming evidence from other sources to support that. To me this is not looking that way, so I treat this with some caution for the time being.

If they are correct then they do indicate that the very persistent belt of high surface pressure to the north of the UK, often recently to the north west may be coming to an end. This may be the reason that the GFS outputs beyond T+192 have recently been a sort of ‘nothingness’ over much of the North Atlantic/Europe area.

So as ever conflicting evidence as to what may happen up to the end of June.

My punt would be for the high pressure zone to weaken, for the 500mb trough, or even a cut off 500mb circulation, to be a fairly large player in our weather, and much of that ‘play’ showing the unsettled side of its trough.

Thus for a prediction which is not that different from the one last Friday.

The south east to do best in terms of less rainfall and higher temperatures, (at times almost into very warm), and the further north and west in the UK you live then the situation being reversed. That is more unsettled with more belts of rain as lows track near to their usual corridor to the north west of the UK, most of the time, also rather breezy at times, and with temperatures only now and then edging above normal. There is the probability that on a very temporary basis as a southerly develops ahead of a low moving east that the south and south east could get a heavier burst of thundery type rain along with the higher temperatures I’ve mentioned.

[johnholmes]

No 14 - Update on Friday 20th for 27 June-6 July

Average temperatures for the period are:-

14+ for the N Isles to 18-19+ for Scotland and N Ireland, mostly 20+ for England and Wales with London on 21+.

For links to explain various terms and their use see earlier posts on this thread.

Into the second month of official summer and is the heat wave on the way?

Short answer is no, certainly nothing in any of the links/teleconnections/models to suggest anything looking like a heat wave, especially if its one of several days and countrywide you are looking for.

Looking at the various inputs first.

ENSO

This is the link http://www.cpc.ncep.noaa.gov/products/anal...s-fcsts-web.pdf

It was last updated 16 June and the main features were; neutral conditions are expected through the northern hemisphere summer.

AO

This shows first a fall then a rise with the expected scatter at that range.

NAO

Well below zero at the moment with a prediction of a rise but not really into +ve territory.

Turning to the 10 day ECMWF and GFS 500mb anomaly charts and how they have changed over the past few days. The latest one is below.

This appears to be a fairly logical and believable series of chart up to the one shown below. –ve values to the west of the UK on both models (ECMWF is the one on the left, GFS on the right). One interesting thing is the 'link' from that –ve area right up into north Russia over the pole. It also shows the +ve area over Europe which has shown signs of increasing. The 576 DM line has moved north over the past week (on the forecast that is). Perhaps a favourable sign for into July?

The NOAA equivalent in the 8-14 day period (27 June -3 July) on their 500mb anomaly chart is below. It is for a few days later than the one above and seems to suggest that the –ve values are moving into the Uk with little sign of any real +ve values at 500mb over Europe affecting the country.

Looking at the GFS ensembles for pressure running out into July and we see, using Derbyshire as mid country)

It shows a fair amount of agreement to around 29 June before it, as one would expect at this range, it diverges much of the time although it is trying to suggest a return to a higher value again by the end of the first week in July. Certainly the unsettled spell each model is showing well before this time scale, next week, is pretty well indicated with alternate high and low pressures as the 500mb trough allows a succession of surface low pressure with ridges in between to swing in from the south west.

The forecast for the period 27 June – 6 July

I believe it's a 'typical summer' pattern, in that the flow will be south of west for much of the time. There is, to me, no sign from any source of a major block developing over Europe along with a major trough setting up in a stationary mode in mid to east Atlantic. This would give the, it seems, much sought after, southerly with the air originating, depending on the exact positioning of the two major players, from off Europe or from way down further south. To me this is not going to happen in this time scale.

So not settled for any period of more than a day or so, and even then that is usually going to be for the south east part of the country.

Always more unsettled the further north and north west in the UK you live, always less unsettled the further south and east, and obviously the temperature levels will reflect this. Much of the time for that south east quarter the values will be around or above the values quoted at the top. hardly hot but much of the time above those values. The exceptions will be when any low tends to dig further south than its usual track to the north west of mainland Scotland and until a mobile ridge builds in behind it, then a temporary spell of unsettled weather in that south east area. Breezy conditions could also surround perhaps just one such low although less so than in the immediate future.

One other player not so far seen is the hurricane development and how that may interact over the UK area. So far there is no real indication of any such development. They are more normally seen in the latter half of the meteorological summer.

The next update will be Tuesday 24 June for the same time period.

Validation checks for this and the Tuesday forecast (No 15) will be 27 June and 6 July.

[bluearmy]

i asume you are working hard on tonights update JH.

do you think it significant that on todays cpc 6/10 day output, where ecm is heavily weighted, the atlantic trough is set that bit further west whereas, once we get to the 8/14 day chart with GFS/GEM only, the trough is back over the UK???? there certainly looks to be more of an appetite today for a warm southerly drift as we possibly get squeezed between an atlantic trough and a block to our north east.

[johnholmes]

its in its 'gestation' period and soon to be issued Nick.

Yes NOAA seem not too happy at the models suggesting a wave change over their area. 6-14 days it covers in their chat. Their own 500mb anomaly charts, first hint at a Euro high then, and this is the third day its happened, they then take it away. The wave length over the States and out into Europe is favourable for no rapid and large changes at 500mb, the trough moving first east then warming out then reforming in the western Atlantic and swinging east. Whether, say into the first week of July this will develop into the trough - ridge in the 'right' place for a southerly is not clear, at any rate not to me.

Anyway all to be revealed shortly.

Edited June 24, 2008 by johnholmes