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Met office Contingency planners forecasts

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As well as the updates for the monthly outlooks the met office also issue a Contingency planners forecast every month which covers a 3 month period these are issued for the public sector but they can also be very useful for the general public, these forecasts cover both precipitation and temperature

The December update was issued on the 20th of December

Temperature

Summary - Temperature

For January as a whole below-average UK-mean temperatures are somewhat more likely than above-average, although there is considerable uncertainty. Similarly, snow and ice may occur more often than they do in an average January. For February and March the range of possible outcomes is also very broad, although above-average UK-mean temperatures become more likely. Overall, the probability that the UK-mean temperature for January-February-March will fall into the coldest of our five categories is around 15% whilst the probability that it will fall into the warmest of our five categories is around 20% (the 1981-2010 probability for each of these categories is 20%).

Context

Sea surface temperatures in the tropical Pacific remain in a neutral El Niňo/La Niňa phase, and this is expected to continue through the forecast period. This phase has no known predictive value for northwest Europe. Meanwhile sea temperatures in the northwest Atlantic remain well above average. This is especially true around Newfoundland, where observations show that unusually high values – more than 4 degrees Celsius above average - extend to considerable depth.

Around much of the Arctic, sea surface temperatures are also above average. Similarly, Arctic sea ice extent, although undergoing the usual winter-time increase, remains at a near-record low level for the time of year, with the Barents Sea northeast of Scandinavia showing a particularly large deficit. Although we are dealing here with an emerging area of scientific research there are suggestions that the aforementioned patterns can favour blocked weather types that bring cold northerly or easterly winds to northwest Europe.

Computer forecast models show considerable spread in their handling of the weather in the January-February-March period, although the new high resolution model just introduced at the Met Office, which exhibits more skill in forecast reruns for the past, favours cold conditions over warm during January. Some model scenarios suggest that during January the UK could be the battleground between cold air of Scandinavian or Russian origins, and mild Atlantic air, meaning that substantial changes in weather type are quite possible, although equally one or other type could prevail.

Some heavy snow can be expected at the boundary between the warm and cold air, although whether that would be over the UK is far from clear. As we move into February and March mild westerly or southwesterly winds become more likely, although cold outbreaks are still possible. The forecast curves in Figure T2 reflect all of the above, showing a shift towards colder-than-average values for January, and a structure that is close to climatology for January-February-March as a whole. On the left panel of Figure T2 note also how the bulk of the pink forecast points lie below last year’s value (labelled 2012), suggesting a high probability that January will be colder than last year.

Precipitation

Summary - Precipitation

Predictions for UK-mean precipitation are very uncertain, although for the January-February-March period as a whole above-average values are a little more likely than below-average. The saturated state of the ground means that there will be a high sensitivity to heavy rainfall events early in 2013, and should a wetter-than-average outcome be realised impacts in terms of flooding could be very significant. The probability that UK precipitation for January-February-March will fall into the driest of our five categories is around 15% and the probability that it will fall into the wettest category is around 20% (the 1981-2010 probability for each of these categories is 20%).

Context

Predictability of UK precipitation on seasonal timescales is generally low. For the early part of January there is some consistency in the computer forecasts, with low pressure and frontal systems favoured across the UK, which could bring heavy rain, and possibly some snow. In addition these patterns imply a heightened risk of windstorms. Beyond early January however the various forecasts diverge considerably, with a wide range of weather types possible. If westerly or southwesterly winds prevail, rainfall would be more likely to be above average, particularly in the west of the UK. However, in a colder easterly or northerly type below-average UK precipitation would be more probable (although snow would then become much more likely). As discussed in the temperature section, we could see transitions between these two weather types, which could thus mean alternating relatively wet and relatively dry spells for the UK.

As a legacy of many months with above-average rainfall (see blue line on figure P1), and indeed further heavy rainfall events in the run up to Christmas, it is clear that the ground will be in a saturated state at the start of January across most of the UK. This greatly enhances sensitivity to rainfall, heightening the risk of fluvial or pluvial flooding should heavy rain occur. So from the above we have to conclude that the risk of flooding is much higher than average, at least at the start of the January-February-March period. To re-iterate the uncertainties in the rainfall forecast, note how the pink and blue forecast points on the graphs on Figure P2 essentially span the whole range of outcomes observed in the last 32 years (black and grey stars), and how the related forecast distribution curve, for January at least, is relatively flat, suggesting that no particular outcome is favoured.

http://www.metoffice.gov.uk/publicsector/contingency-planners

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Bugger.

ALTHOUGH that doesn't mean we can't see a below average winter, does it? Posted Image

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u say u don't take much noatis of the met's longrange forecasts after their spring forecast, if u remembor nw forecasted a summer with shades of 76 wich didn't come off, and the w2012-w2013 apart from first 2weeks it hasn't been that cold and the met got that wrong too but it looks like most of jan gona be mild going by the models.

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u say u don't take much noatis of the met's longrange forecasts after their spring forecast, if u remembor nw forecasted a summer with shades of 76 wich didn't come off, and the w2012-w2013 apart from first 2weeks it hasn't been that cold and the met got that wrong too but it looks like most of jan gona be mild going by the models.

Not a go at the Met Office Per Se as there were other forecasts that were wrong. After reading earlier in the spring that the drought would continue and the temps would be above average I cannot take the 3 month forecast seriously. Still searching for a reliable long-range forecaster, when your livelihood is affected by the weather they are quite handy! Looks like its just me looking at the model output and reading the thoughts of those more expert than I for the foreseeable!

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hey i wasn't having ago at u i just wanted to make the point that other forecasters get it wrong too. Sorry if my post came across like that.

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hey i wasn't having ago at u i just wanted to make the point that other forecasters get it wrong too. Sorry if my post came across like that.

Sorry Syed, I didn't think you were having a go,I just wanted to explain that I haven't found a good long range forecaster.I don't think they exist. If the Met's 3month forecast improves then I might start to take notice.

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Sorry Syed, I didn't think you were having a go,I just wanted to explain that I haven't found a good long range forecaster.I don't think they exist. If the Met's 3month forecast improves then I might start to take notice.

LRF's are little more than educated guess work it seems to me, of all the ones I've read over the years they're about as often wrong as they are right. That Met Office spring forecast couldn't be more spectacularly wrong if they tried! Not bashing the Met Office though, it's just very very difficult due to the chaotic nature of the atmosphere and how little we understand how all the various factors and pieces fit together. I don't think they will ever improve much either due to chaos and the laws of diminishing returns.

Sometimes I think it'll be a lot simpler if the models only went out to say +168 and nobody took much notice beyond then.

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Take one look at the ensembles and watch the scatter after 5 days then imagine the scatter after six weeks. It becomes climatology rather than meteorogy after a few weeks looking for trends. Most will know what looking for trends did for us a few weeks ago and that was ten days ahead. Remember thou that they say something like 55% chance. That means 45% chance it will not be true. most of us on here do have an understanding on how complicated and chaotic this science is so there is no critism of meto. Infact 5 days out they are very good indeed. We just do not have ability to put all equations together for long term in to a computer.

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i think we r stil quite along way from accuret lrf's yet. Though i take my hat off to those who produce1 accept james maddin of course.

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January updated issued

Temperature

For February below-average UK-mean temperatures are more likely than above-average, although there is considerable uncertainty. As a consequence, snow and ice may be more prevalent than in an average February. For February-March-April as a whole, near-average temperatures are more likely. Overall, the probability that the UK-mean temperature for February-March-April will be in either the coldest or warmest of our five categories is between 15% and 20% (the 1981-2010 probability for each of these categories is 20%).

Temperatures in the northwest Atlantic remain well above average, at surface and at depth, especially near the coast of Newfoundland. Around much of the Arctic, sea surface temperatures are also above average and amounts of sea ice below average, particularly northeast of Scandinavia. These factors, along with a tendency for winds high in the atmosphere to be weak during February, typically allow blocking patterns to develop more readily across northwestern Europe. These weather patterns can bring easterly or northeasterly winds to the UK, which during late winter are often cold. Indeed, computer model forecasts agree in predicting a pattern of atmospheric circulation indicating anomalously negative North Atlantic Oscillation conditions.

This usually favours colder-than-average conditions over northern Europe; however, the chance of cold weather across the UK is finely balanced. Some model scenarios suggest that the UK could be the battleground between cold air from northern Europe and milder Atlantic air. Such a scenario would bring a risk of heavy snow at the boundary between the two air masses. As we move into March and April milder weather becomes more likely, although cold outbreaks are still possible. The forecast curves in Figure T2 show a shift towards colder-than-average values for February and a preference for near-average values for the February-March-April period as a whole.

Precipitation

As is often the case, predictions for UK mean precipitation are uncertain; for the February-March-April period as a whole near-to slightly-below-average amounts are most probable. The probability that UK precipitation for February-March-April will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is around 15% (the 1981-2010 probability for each of these categories is 20%).

The temperature section discusses the atmospheric circulation patterns favoured in the forecast; these would usually be associated with drier-than-average conditions over northern Europe. However, as for temperature, the precise detail of the pattern plays a crucial role in the distribution of precipitation across the UK, with even small shifts in the position of the main centres of action likely to create significant regional variations.

Current model predictions show a weak signal for below-average seasonal precipitation over northern parts of the UK, and the opposite for southern parts. This signal is most evident in the first part of the forecast period, when the risk of below-average temperature is also enhanced; this would imply snow is more likely than usual at this time of year.

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they cant forcast for two weeks never mind 3 months.what about the barbacue summer.the swansea ball boy could give a better forcast!!!!!!!!!!

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March update issued

Summary Temperature:

For March below-average UK-mean temperatures are more likely than above-average. For March-April-May as a whole, near-average temperatures are more likely, although uncertainty for the period is larger. The probability that the UK-mean temperature for March-April-May will be in the coldest of our five categories is between 15% and 20% and the probability that it will be in the warmest of our five categories is also between 15% and 20% (the 1981-2010

Neutral conditions (neither El Niño nor La Niña) continue in the Tropical Pacific; forecasts indicate continuation of such conditions as the most likely scenario over the next three months.Temperatures in the northwest Atlantic are still above average, at surface and at depth, especially near the coast of Newfoundland. The Madden Julian Oscillation currently shows moderately enhanced activity in the western Pacific. These factors typically allow blocking patterns to develop more readily across northwestern Europe and can bring easterly winds to the UK, which in early spring are often cold.

Models agree with this scenario, predicting a pattern of atmospheric circulation indicating anomalously negative North Atlantic Oscillation conditions, which usually favour colder-than-average conditions over northern Europe. As we move into April and May the relationship between blocking patterns and colder weather is weaker; indeed, by late spring, blocking patterns can bring warmer-than-average conditions to northern Europe and the UK.

The forecast curves in Figure T2 show a shift towards colder-than-average values for March. During April and May the general atmospheric circulation over the North Atlantic region is predicted to be more westerly than in recent months, but signals for UK temperature are weak. For March-April-May as a whole, the outer categories are equally likely, with probabilities of near-average conditions slightly higher than climatological values.

http://www.metoffice...ts-temp-MAM.pdf

Summary - Precipitation:

Consistent with below-average temperatures, rainfall during March is more likely to be below average than above average. For the March-April-May period as a whole near- to below-average rainfall amounts are most probable. The probability that UK precipitation for March-April-May will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is around 15% (the 1981-2010 probability for each of these categories is 20%)

As already discussed in the temperature section, blocking patterns are favoured across northwestern Europe during the early part of the spring. Typically, such patterns are associated with drier-than-average conditions over northern Europe. For the UK drier-than-average conditions are more likely, especially in March. Indeed, forecast models are predicting rainfall most likely near- to below-average or somewhat below average through the whole period. As with temperature, a return to a more westerly circulation pattern in the latter part of spring would favour near-average rainfall amounts.

The forecast curves in Figure P2 show a shift towards drier-than-average values for March and a slight preference for drier-than-average values for the March-April-May period as a whole, although note that in the latter there is a larger spread of solutions, indicative of confidence being lower for the period as a whole

http://www.metoffice...-precip-MAM.pdf

Edited by Gavin.

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April update Issued

Summary Temperature:

For April below-average UK-mean temperatures are more likely than above-average. For April-May-June as a whole above-average temperatures are weakly favoured. However, there is still a significant chance that this period will be colder than it was in the majority of the last 10 years

Neutral conditions (neither El Niño nor La Niña) persist in the Tropical Pacific. Forecasts suggest a continuation of these conditions as the most likely scenario during the next three months. Arctic sea ice is around normal coverage for the time of year. However, any impact of this on spring-time conditions remains unclear. Although large-scale drivers are very weak, perhaps most significant on this occasion are the anomalously low sea surface temperatures over much of the North Sea, with below-average values also present around all other coasts of the British Isles. These colder than normal sea temperatures are likely to persist for at least a month. The Met Office models suggest a dominance of higher-than-average sea-level pressure over Scandinavia and lower-than-average pressure to the southwest of Britain during April. This would favour an increased chance of winds from an easterly quarter.

Given the colder-than-normal North Sea, easterly air streams in April are likely to give below-average temperatures, especially in the east. In addition, the very wet ground could also lead to increased cloudiness, generally suppressing temperatures across the UK. Low sea temperatures could also lead to an increased chance of fog and low cloud affecting coastal regions, in particular near the North Sea. For April-May-June as a whole there is a slight preference for above-average temperatures, with the colder-than-average conditions in April being offset by some warm spells later in the season.

http://www.metoffice...ts-temp-AMJ.pdf

Summary Precipitation:

For both April and April-May-June as a whole the uncertainty is large, leaving the forecast largely indistinguishable from climatology. The probability that UK precipitation will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is also around 20% (the probability for each of these categories is 20%)

Climatologically, spring is the driest season of the year, as shown in Figure P1. In general, through spring rainfall becomes increasingly difficult to predict given that the likelihood of localised convective rainfall increasingly dominates the rainfall distribution. With the ground virtually saturated over some considerable depth following periods of very wet weather over the past year, increased evapo-transpiration could further increase the risk of heavy convective rainfall as the season progresses. As the ground is also saturated over much of continental Europe, any air streams from the south or southeast will likely bring an enhanced risk of heavy convective rainfall.

For the latter part of the period model signals become weak, but favour transition to westerly or southwesterly winds, which would suggest periods of unsettled weather. However, the signals from models, for rainfall amounts through the spring, are very indeterminate and largely indistinguishable from climatology.

http://www.metoffice...-precip-AMJ.pdf

Edited by Gavin.
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That seems a very sensible well argued forecast given the current level of understanding for predicting 3 months ahead.

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April update Issued

Summary Temperature:

For April below-average UK-mean temperatures are more likely than above-average. For April-May-June as a whole above-average temperatures are weakly favoured. However, there is still a significant chance that this period will be colder than it was in the majority of the last 10 years

Neutral conditions (neither El Niño nor La Niña) persist in the Tropical Pacific. Forecasts suggest a continuation of these conditions as the most likely scenario during the next three months. Arctic sea ice is around normal coverage for the time of year. However, any impact of this on spring-time conditions remains unclear. Although large-scale drivers are very weak, perhaps most significant on this occasion are the anomalously low sea surface temperatures over much of the North Sea, with below-average values also present around all other coasts of the British Isles. These colder than normal sea temperatures are likely to persist for at least a month. The Met Office models suggest a dominance of higher-than-average sea-level pressure over Scandinavia and lower-than-average pressure to the southwest of Britain during April. This would favour an increased chance of winds from an easterly quarter.

Given the colder-than-normal North Sea, easterly air streams in April are likely to give below-average temperatures, especially in the east. In addition, the very wet ground could also lead to increased cloudiness, generally suppressing temperatures across the UK. Low sea temperatures could also lead to an increased chance of fog and low cloud affecting coastal regions, in particular near the North Sea. For April-May-June as a whole there is a slight preference for above-average temperatures, with the colder-than-average conditions in April being offset by some warm spells later in the season.

http://www.metoffice...ts-temp-AMJ.pdf

Summary Precipitation:

For both April and April-May-June as a whole the uncertainty is large, leaving the forecast largely indistinguishable from climatology. The probability that UK precipitation will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is also around 20% (the probability for each of these categories is 20%)

Climatologically, spring is the driest season of the year, as shown in Figure P1. In general, through spring rainfall becomes increasingly difficult to predict given that the likelihood of localised convective rainfall increasingly dominates the rainfall distribution. With the ground virtually saturated over some considerable depth following periods of very wet weather over the past year, increased evapo-transpiration could further increase the risk of heavy convective rainfall as the season progresses. As the ground is also saturated over much of continental Europe, any air streams from the south or southeast will likely bring an enhanced risk of heavy convective rainfall.

For the latter part of the period model signals become weak, but favour transition to westerly or southwesterly winds, which would suggest periods of unsettled weather. However, the signals from models, for rainfall amounts through the spring, are very indeterminate and largely indistinguishable from climatology.

http://www.metoffice...-precip-AMJ.pdf

I'm a fan of METO so not having a dig.....but my initial thoughts are that if you put an equal amount on each horse in a 5 horse race at the same odds for each then you cannot lose, of course you cannot win either.....so the net result is 'haven't a clue?' (expect to be shot down for this) Posted Image

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May update issued

 

Summary Temperature:

 

For May-June-July as a whole the balance of probabilities favours UK-mean temperatures relatively close to the 1981-2010 average; the forecast distribution is close to climatology. However, there is still a significant chance that May will follow April 2013 in being cooler than it was in the majority of the last 10 years. The probability that the UK-mean temperature for May-June-July will be in the coldest of our five categories is around 20% and the probability that it will be in the warmest category is also approximately 20% (the climatological probability for each of these categories is 20%).

 

At this time of year the influence of large-scale atmospheric drivers, such as conditions over the Tropical Pacific (which are expected to remain neutral over the next 3 months), on British weather tends to be weaker than in winter. Combined with the absence of any strong signals in the latest model predictions, this leaves predictability of conditions through this period lower than average. However, anomalously low sea surface temperatures currently affecting many British coastal waters, especially the Irish and southern North Sea and through the English Channel, are likely to influence conditions across the UK. These lower than average sea surface temperatures are likely to persist for at least the next few weeks, leaving maximum temperatures most probably lower than what would otherwise be expected for any given weather type, and in particular for easterly types.

 

This all leads to the view that below-average UK-mean temperatures are slightly more likely than above-average during May, although uncertainty remains large, as Figure T2 indicates. Low sea surface temperatures could also lead to an increased chance of fog and low cloud affecting eastern and southern coastal regions. Taking May-June-July as a whole, the absence of large-scale influences is reflected in the forecast distribution being very close to the climatological distribution, as shown in Figure T2.

 

Temperature Summary

 

Summary Precipitation

 

For May below-average precipitation is considered more likely than above-average. For May-June-July as a whole the forecast is largely indistinguishable from climatology. The probability that UK precipitation for May-June-July will be in the driest of our five categories is around 20% and the probability that it will be in the wettest category is also approximately 20% (the climatological probability for each of these categories is 20%).
 

Climatologically late spring and early summer are the driest parts of the year, as shown in Figure P1. The weight of latest model output suggests higher-than-average sea-level pressure dominating near or over the British Isles for at least the first part of May, implying that below-average precipitation is more likely than above-average precipitation for at least part of May.

 

Model signals then become weaker from mid to late May onwards, with an indication of more southwesterly types during June. In the absence of large-scale drivers the forecast suggests that precipitation is likely to be near normal, although the spread of possible outcomes is large. It is worth noting that rainfall at this time of year becomes increasingly difficult to predict due to the likelihood of localised convective rainfall dominating the rainfall distribution and leading to marked regional variability.

 

Precipitation Summary

 

 

 

 

 

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What does this mean in terms of summer?

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What does this mean in terms of summer?

I don't mean to be rude but please read the post above yours, it gives you what you ask for does it not?
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I think there is some value in giving a month ahead forecast even though its probably very rough, but points they make about low seas surface temps etc are of value and model ensembles give some guide out for the start of the period, but I can't see the point in these 3 month forecasts when they are showing such weak signals away from climatology.

 

ie this.

Overall, the probability that the UK-mean temperature for January-February-March will fall into the coldest of our five categories is around 15% whilst the probability that it will fall into the warmest of our five categories is around 20% (the 1981-2010 probability for each of these categories is 20%).

 

So they have a slight warm bias for the three months that were well into the coldest category (would rank between 3rd and 4th coldest in the 1981-2010, so well below 6th which is coldest 20%). But perhaps fair enough given that its mostly due to the final month being exceptionally cold.

 

However we then have the March forecast.

 

For March below-average UK-mean temperatures are more likely than above-average....

The probability that the UK-mean temperature for March-April-May will be in the coldest of our five categories is between 15% and 20% and the probability that it will be in the warmest of our five categories is also between 15% and 20% (the 1981-2010

 

Now after having stated that they expect March to be below average they are still expecting even chances of cold or hot? and incidentally we will almost certainly again fall into the coldest category - would need a May CET of over 14 to beat the 6th coldest in the period.

 

So the question is why make these 3 Month calls if they basically are just saying it will be near average indeed where they differ from this even when they have a short term signal that would be expected to bias the 3 month result lower they still have the chance of very cold being less than normal.

 

If I was contingency planning I can't see how the three month parts would help me at all.

Edited by SomeLikeItHot

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I can only see two alternative approaches the MetO could take: do what James Madden does; make a dog's breakfast of a forecast and then bluff it out, or not make a forecast at all?

 

What should they do, when signals are weak, make it up?Posted Image 

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I can only see two alternative approaches the MetO could take: do what James Madden does; make a dog's breakfast of a forecast and then bluff it out, or not make a forecast at all?

 

What should they do, when signals are weak, make it up?Posted Image 

 

Well obviously they shouldn't make unsupported forecasts so what they are doing is better than that. yes I guess I am suggesting they would be just as well putting up a chart of climate averages. It would save writing a lot of words to get to the same point every month!

 

As I said earlier I am talking about the 3 month part not the one month forecast.

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It would appear that there is a market for such outputs otherwise they would not be prepared!

Edited by johnholmes

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It would appear that there is a market for such outputs otherwise they would not be prepared!

 

Yes no doubt people want to know and will pay. People will also pay for horoscopes, palm readings etc.

 

The met office is giving them a scientific forecast of that I am not doubting, I'm just questioning the actual rather than perceived value of such a forecast.

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June Update issued

 

Summary Temperature

 

For June, below-average UK-mean temperatures are more likely than above-average. For June-July-August as a whole, near-to-below-average temperatures are most probable. Sea surface temperatures of the surrounding seas are below-average, increasing the probability of below-average temperatures across the UK. Overall, the probability that the UK-mean temperature for June-July-August will fall into the warmest of our five categories is 15% and the probability that it will fall into the coldest of our five categories is 20% (the 1981-2010 probability for each of these categories is 20%).

 

Neutral conditions (neither El Niño nor La Niña) have persisted through much of the year so far across the tropical Pacific. Recently below-average sea surface temperatures have been observed close to South America, whilst above-average sea surface temperatures are present around the Philippines and Indonesia. This developing pattern in sea surface temperatures anomalies is consistent with La Niña conditions forming; forecasts from the Met Office seasonal forecasting system indicate a trend towards La Niña conditions over the next few months, but uncertainty is large, with a variety of solutions evident in other models. During the summer months, atmospheric larger-scale drivers, such as those in the tropical Pacific, tend to have less of an influence over weather patterns in northwestern Europe. However, La Niña slightly tilts the balance of probabilities towards cooler, unsettled conditions across northwestern Europe.

Sea surface temperatures across UK waters and the mid North Atlantic continue to remain below average. These cold anomalies are expected to persist for some time (at least another month) increasing the probability of colder-than-average conditions over the period as a whole. The factors described above, along with computer models predicting a preference for westerly or southwesterly flow over the UK, increase the probability of below-average temperatures, although spells of warm weather are still possible. As seen in the forecast curve in figure T2, the probability of below-average temperatures is higher, but above-average temperatures are only slightly less likely than climatology. Low sea surface temperatures could also lead to fog and low cloud affecting eastern and southern coastal regions more frequently than normal this summer.

 

http://www.metoffice.gov.uk/media/pdf/3/g/A3-plots-temp-JJA.pdf

 

Summary Precipitation

 

For June, there is a large degree of uncertainty, but on balance above-average rainfall is more likely than below-average. For the June-July-August period as a whole above-average rainfall is also more probable than below-average rainfall. There is less confidence in the signal emerging in the forecast for rainfall than for temperature. The probability that UK precipitation for June-July-August will fall into the driest of our five categories is around 15% and the probability that it will fall into the wettest category is around 20% (the 1981-2010 probability for each of these categories is 20%).

 

Climatologically June-July-August is wetter than the spring months of March, April and May. This can be attributed to an increase in convective rainfall, rather than large-scale storm systems that are more typical in autumn and winter. UK-average rainfall at this time of year becomes increasingly difficult to predict –  because of its convective and localised nature – and there is often more regional variability. During the summer season below-average temperatures are typically associated with above-average rainfall.

 

As discussed in the temperature section, forecast models indicate an increased probability of westerly or southwesterly types, with a greater likelihood of air masses from a relatively cold maritime source rather than a warm continental one. This more mobile weather pattern not only favours colder-than-average conditions in summer, but also wetter-than-average. This is reflected in the forecast in figure P2, which shows a shift to above-average rainfall, although the probability of conditions being as wet as last year is low. The forecast curve shows a large spread of solutions, with the probability of drier-than-average only slightly lower than climatology.

 

http://www.metoffice.gov.uk/media/pdf/2/n/A3-plots-precip-JJA.pdf

 

 

 

 

 

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