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Met office Contingency planners forecasts

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Thanks for that, Gav...It's far better than the (for some reason more popular) 'watch out for heavy storms on July 23' sort of twaddle...

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On reflection on my earlier comments on this thread were a bit harsh. i don't entirely disagree with anything I said but on reflection there probably is some value in these beyond climatology - particularly when I reflect that a contignency planner is less likely to be aware of pervasive factors such as the state of el Nino/la nina and adjacent sea surface temperatures than I am. 

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It has been a while since I updated this thread but here is the updated they issued at the end of July

 

August to October

 

Summary Temperature
 
Latest predictions for UK-mean temperature slightly favour above-average values for both August and August-September-October. Overall, the probability that the UK-mean temperature for August-September-October will fall into the warmest of our five categories is 25% and the probability that it will fall into the coldest of our five categories is 10% (the 1981-2010 probability for each of these categories is 20%)
 
As in recent months, near neutral conditions (neither El Niño nor La Niña) remain across the tropical Pacific. However, below-average sea surface temperatures continue to be observed close to South America, whilst across the Philippines and Indonesia above average sea surface temperatures persist. This pattern in sea surface temperature anomalies is consistent with weak La Niña conditions; forecasts from the Met Office seasonal forecasting system indicate a trend towards either neutral or La Niña conditions over the next few months, but uncertainty is large, with a variety of solutions evident in other models. No clear influence on weather patterns over Europe can be anticipated at this stage, in part because the influence of El Niño and La Niña is usually weaker at this time of year than in winter. Computer models show a preference for the August-mean sea-level pressure to be slightly lower than normal over the UK region. Whilst such a pressure pattern would slightly favour stronger-than-average westerly winds, it does not preclude periods of more settled weather. For the month as a whole there is a slight preference for warmer-than-average conditions across the UK. For August-September-October as a whole, the mean surface pressure signal is weak, although there is some variation between the months. Therefore, although above-average temperatures are favoured over the season as a whole, this does not exclude the possibility of spells of cool weather

 

http://www.metoffice.gov.uk/media/pdf/i/7/A3_plots-temp-ASO.pdf

 

Summary precipitation

 

The balance of probabilities suggests that the dry, settled conditions experienced in July may not persist through August; currently near-to-above-average rainfall is slightly favoured. For August-September-October as a whole the signal is largely indistinguishable from climatology. The probability that UK precipitation for August-September-October 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 20% (the 1981-2010 probability for each of these categories is 20%)
 
As discussed in the temperature section, there is a slight tendency for lower-than-normal surface pressure over the UK region, for August as a whole. Such a pattern can to lead to wetter-than-average conditions. However, the signal for above-average precipitation is weak, suggesting scope for some more settled spells of weather as well. The forecast curve on the left in figure P2 does show a wide range of possible outcomes, giving large uncertainty in the forecast. For the August-September-October period there is little signal in the forecast for surface pressure, and consequently in the seasonal average rainfall. This is reflected in the curve on the right of figure P2, which is largely indistinguishable from climatology.
 

 

 

 

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Here is the September update

 

September to November

 

Summary Temperature

 
Latest predictions for UK-mean temperature favour above-average temperatures for September-October-November. Overall, the probability that the UK-mean temperature for September-October-November will fall into the warmest of our five categories is 25% and the probability of falling into the coldest of our five categories is 15% (the 1981-2010 probability for each of these categories is 20%)
 
There is little change in the state of sea surface temperature anomalies in the tropical Pacific, with near-neutral conditions (neither El Niño nor La Niña) continuing; computer models indicate little change in the coming months. This phase has no known predictive value for northern Europe on seasonal timescales. Also, there are no other major large-scale drivers of seasonal predictability evident in, for example, the global ocean temperatures. For September-October-November as a whole, the forecasts favour slightly higher-than-average pressure over northern Europe, suggesting blocking patterns may be more prevalent. This period is a transitional time of year in which a given circulation pattern can result in very different temperature outcomes between the beginning and the end of the season. For example, a pattern with frequent spells of winds from continental Europe during September and early October often gives warm weather over the UK, whereas a similar pattern towards the end of October and throughout November leads to the converse. Therefore, although above-average temperatures are favoured for the season as a whole, this does not exclude spells of colder weather, especially later in the period

 

 
http://www.metoffice.gov.uk/media/pdf/7/7/A3-plots-temp-SON_v2.pdf

 

Summary precipitation

 

For September-October-November as a whole the forecast signal is similar to climatology, but with slightly higher probabilities for near-average rainfall. The probability that UK precipitation for September-October-November 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 15% (the 1981-2010 probability for each of these categories is 20%).
 
Autumn is regarded as a season of transition from summertime to winter time weather patterns and is notorious for unsettled conditions. As cold polar air moves progressively further south, it meets warm air from the tropics, creating strong temperature gradients. Large temperature contrasts combined with a warm ocean, which has been heated throughout the spring and summer, produce the unsettled weather of autumn. Consequently Atlantic depressions typically become more intense, often carrying large amounts of moisture, making autumn generally the stormiest and wettest time of year, as can be seen figure P1. The remnants of hurricanes moving north and east across the Atlantic can also contribute to making depressions at this time some of the most intense and wettest of the year.  For the September-October-November period there is a preference in the forecast for pressure to be higher than average across northern Europe. As noted for temperature, this is a transitional period where the association between circulation and rainfall changes through the period. Overall, the forecast is largely indistinguishable from climatology, although with a slight preference for near-average conditions. However, the slight reduction in the risk of a very wet season overall does not exclude the possibility of some periods of heavy rainfall due to the enhanced risk of stormy weather discussed above

 

http://www.metoffice.gov.uk/media/pdf/7/4/A3-plots-precip-SON_v2.pdf

 

 

 

 

 

Edited by Summer Sun
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Here is the September update

 

September to November

 

Summary Temperature

 
Latest predictions for UK-mean temperature favour above-average temperatures for September-October-November. Overall, the probability that the UK-mean temperature for September-October-November will fall into the warmest of our five categories is 25% and the probability of falling into the coldest of our five categories is 15% (the 1981-2010 probability for each of these categories is 20%)
 
There is little change in the state of sea surface temperature anomalies in the tropical Pacific, with near-neutral conditions (neither El Niño nor La Niña) continuing; computer models indicate little change in the coming months. This phase has no known predictive value for northern Europe on seasonal timescales. Also, there are no other major large-scale drivers of seasonal predictability evident in, for example, the global ocean temperatures. For September-October-November as a whole, the forecasts favour slightly higher-than-average pressure over northern Europe, suggesting blocking patterns may be more prevalent. This period is a transitional time of year in which a given circulation pattern can result in very different temperature outcomes between the beginning and the end of the season. For example, a pattern with frequent spells of winds from continental Europe during September and early October often gives warm weather over the UK, whereas a similar pattern towards the end of October and throughout November leads to the converse. Therefore, although above-average temperatures are favoured for the season as a whole, this does not exclude spells of colder weather, especially later in the period

 

 
http://www.metoffice.gov.uk/media/pdf/7/7/A3-plots-temp-SON_v2.pdf

 

Summary precipitation

 

For September-October-November as a whole the forecast signal is similar to climatology, but with slightly higher probabilities for near-average rainfall. The probability that UK precipitation for September-October-November 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 15% (the 1981-2010 probability for each of these categories is 20%).
 
Autumn is regarded as a season of transition from summertime to winter time weather patterns and is notorious for unsettled conditions. As cold polar air moves progressively further south, it meets warm air from the tropics, creating strong temperature gradients. Large temperature contrasts combined with a warm ocean, which has been heated throughout the spring and summer, produce the unsettled weather of autumn. Consequently Atlantic depressions typically become more intense, often carrying large amounts of moisture, making autumn generally the stormiest and wettest time of year, as can be seen figure P1. The remnants of hurricanes moving north and east across the Atlantic can also contribute to making depressions at this time some of the most intense and wettest of the year.  For the September-October-November period there is a preference in the forecast for pressure to be higher than average across northern Europe. As noted for temperature, this is a transitional period where the association between circulation and rainfall changes through the period. Overall, the forecast is largely indistinguishable from climatology, although with a slight preference for near-average conditions. However, the slight reduction in the risk of a very wet season overall does not exclude the possibility of some periods of heavy rainfall due to the enhanced risk of stormy weather discussed above

 

http://www.metoffice.gov.uk/media/pdf/7/4/A3-plots-precip-SON_v2.pdf

 

 

 

 

 

 

 

So basically they expect the air to mainly originate more from the Continent this Autumn (which for a time is still mild), hopefully that will switch around by late October before things start to freeze over there and we get a different wind direction. Obviously the Met Office don't discount some Autumnal storms too so some Atlantic influence at times.

Edited by Gaz1985

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Just looking over these forecasts posted here, and diging out the one for July. It seems on the temperature frecast for the one month period they have been broadly correct on 7/8 occasions (the one miss was calling July as cooler than average). On the three month time frame however they were correct only 1 out of 6 (May-June-July was near average)

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Broadly speaking these forecasts for temperature have been really quite bad. You wouldn't expect them to go into depth 3 months ahead granted but they basically repeat what they say everytime with very little deviation. Atleast they try.

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Update for September issued
 
October to December
 
Temperature

 

Indications are that October will most likely be slightly warmer-than-average. For October-November-December as a whole uncertainty is large with above- and below-average temperatures both equally probable. Overall, the probability that the UK-mean temperature for October-November-December will fall into either the warmest or the coldest category is between 20 and 25% (the 1981-2010 probability for each of these categories is 20%)

 

There are currently no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña conditions prevail. Computer models favour a continuation of near-neutral conditions in the coming months. In the mid-North Atlantic sea surface temperatures are above average, whilst further north sea surface temperatures are a little below average. The influence of these forcing factors is weak and not expected to contribute predictive value for conditions across Europe over the next three months.
 
Arctic sea ice has just reached its annual minimum extent, which is still well below the climatological average but not as low as last year’s record minimum. Whilst this might play some part in determining the weather over the northern hemisphere during winter, as yet there is no clear predictive association. The lack of strong influences, described above, suggests that predictability for the coming three months is low. However, models have a weak signal for slightly higher-than-average pressure to the north of the UK, suggesting a slight weakening of the prevailing mean westerlies, which could allow a greater-than-average incidence of blocking patterns. This period is a transitional time of year in which a given circulation pattern can result in very different temperature outcomes between the beginning and the end of the season.
 
For example, a blocked pattern in October could lead to warmer-than-average conditions, whereas in November and December will most likely be associated with lower-than-average temperatures. This is reflected in the temperature forecast for October-November-December, with warmer-than-average and colder-than-average outcomes both equally probable and slightly enhanced relative to climatology – as can be seen on the right of figure T2.

 

http://www.metoffice.gov.uk/media/pdf/5/7/A3_plots-temp-OND.pdf

 

Precipitation

 

Confidence in the forecast for precipitation across the UK over the next three months is low. There is a preference for near-to-below-average rainfall during October. For October-November-December as a whole the signal is similar to climatology, although with a slightly higher probability of above-average rainfall. The probability that UK precipitation for October-November-December 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 20% (the 1981-2010 probability for each of these categories is 20%).
 
At this time of year, climatologically speaking, Atlantic depressions typically become more intense, often carrying large amounts of moisture, making the latter part of autumn and early winter often the stormiest and wettest part of the year, as can be seen in figure P1. As discussed in the temperature section, the lack of large-scale forcing means that there is large uncertainty in the forecast for the next three months. Forecast models indicate a slight weakening of the prevailing westerly flow, but the effect of such a circulation pattern on UK precipitation at this time of year is unclear. There is no significant increase in the probability of a very wet or very dry season with respect to climatology, however the probability of a near-to-above-average rainfall for October-November-December is slightly enhanced – as can be seen on the right of figure P2

 

http://www.metoffice.gov.uk/media/pdf/4/g/A3_plots-precip-OND.pdf

 

Edited by Summer Sun

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Not much to get over exited about there then...at least not yet!

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October update issued

 

November to January

 

Temperature

 

There is a strong signal in the forecast for above-average November-mean temperatures. For November-December-January above-average temperatures are considered more likely than below, though this signal is likely strongly influenced by the expected mild November. Overall the probability that the UK-mean temperature for November-December-January will be in the warmest of our five categories is close to 30% and the probability that it will fall into the coldest category is approximately 15% (the 1981-2010 probability for each of these categories is 20%). 

There are currently no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña conditions prevail. In this respect computer models favour a continuation of neutral conditions during the coming months, leaving the influence of this as a forcing factor weak and not expected to contribute predictive value for conditions across Europe during the next three months. Across a large part of the North Atlantic sea surface temperatures remain largely above average, whilst further north Arctic sea ice has recently reached its annual minimum extent. Whilst well below the climatological average, this minimum extent was not as low as 2012’s record minimum.

 

The greatest deficit relative to average appears to be over the northern Barents and Kara Seas. Whilst this may play some part in determining late autumn and early wintertime conditions over northern Europe, the predictive associations are not yet entirely clear. Tropical stratospheric conditions, meanwhile, are now in a strong westerly Quasi-Biennial Oscillation phase, which has an established link to autumn and winter time conditions over northwestern Europe, favouring positive North Atlantic Oscillation.

 

Latest computer model forecasts indeed favour westerly or southwesterly atmospheric flow over northwestern Europe, including the UK. At this time of year this is typically associated with milder-, wetter- and stormier-than-average conditions. These influences are reflected in the forecast in Figure T2, which shows a strong signal for milder-than-average conditions in November.

 

In fact the forecast indicates a high probability of a milder November than that of last year. This is likely to be associated with lower-than-average incidence of overnight frost. Forecast curves for November-December-January indicate above-average temperatures more likely than below-average. However, even during milder winters occasional colder outbreaks can still occur more especially in December and January.

 

http://www.metoffice.gov.uk/media/pdf/3/q/A3_plots-temp-NDJ.pdf

 

Precipitation

 

Indications are that precipitation in November is more likely to be above average than below average. For November-December-January as a whole the signal for precipitation is similar to climatology, with only a slightly higher probability of above-average than below-average rainfall. The probability that UK precipitation for November-December-January will fall into the driest of our five categories is close to 15% and the probability that it will fall into the wettest category is approximately 25% (the 1981-2010 probability for each of these categories is 20%). 

At this time of the year, climatologically speaking, Atlantic depressions are typically more intense, affect Britain more frequently and often carry large amounts of moisture making the late autumn and early winter one of the stormier and wetter parts of the year. As discussed in the temperature section, one atmospheric driver with known influence on predictability over northwestern Europe at this time of year is in a phase conducive to positive North Atlantic Oscillation. This typically favours wetter-than-average conditions, as well as an increased risk of windier periods or storms and heavy rainfall, over northwestern Europe during the late autumn and early winter. Later in this forecast period computer models show large spread, and hence increased uncertainty, concerning likely dominant synoptic types.

 

Forecast curves for November show a strong signal for wetter-than-average conditions. With computer models signalling westerly or southwesterly flow for November as a whole, it is thought more likely than not that many northern and western parts of Britain would be wetter than in November 2012. For November-December-January as a whole the forecast favours above-average rainfall over below-average, with the probability of very wet conditions enhanced, and that for very dry conditions reduced, with respect to climatology. 

http://www.metoffice.gov.uk/media/pdf/2/q/A3_plots-precip-NDJ.pdf

Edited by Summer Sun
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an interesting forecast not really good news for the coldies though. Or have i got that wrong?

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an interesting forecast not really good news for the coldies though. Or have i got that wrong?

 

Based on this months update you would be right in saying not really good news for the coldies, based on the update something like winter 11 / 12 springs to mind mostly mild with limited cold snaps

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For the snow hunters though there are some positive grains in there, although temps may be on the whole higher there is also a signal of wetter than average, if the PPN hits in line with the cold spells we could be in luck.

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Based on this months update you would be right in saying not really good news for the coldies, based on the update something like winter 11 / 12 springs to mind mostly mild with limited cold snaps

Look at there summer probability forecast, if the winter one is as good as that one then us coldies are In for a good one.
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November updated Issued

 

December to February

 

Summary Temperature

 

Indications are that December will most likely be colder than average. For December-January-February as a whole uncertainty is quite large but below-average temperatures are more likely than above-average. Overall, the probability that the UK-mean temperature for December-January-February will fall into the coldest category is between 20 and 25% and the probability that it will fall into the warmest category is between 10 and 15% (the 1981-2010 probability for each of these categories is 20%). 

The most useful indicator of synoptic type during the winter months is the North Atlantic Oscillation (NAO) which in its positive mode results in stormy winters across the UK with generally milder-than-normal temperatures. A negative NAO is mostly associated with fewer storms than normal, a pre-dominance of high pressure and generally lower-than-normal temperatures as outgoing long-wave radiation overnight is greater than normal. There are currently no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña conditions prevail. Computer models favour a continuation of near-neutral conditions in the coming months. In the northwest Atlantic sea surface temperatures are mostly above average, whilst further south they are a little below average. The influence of these forcing factors is to weaken the strength of jetstreams in the Atlantic, creating a less conducive environment for storms and more dominant high pressure systems over the UK, that is, negative NAO conditions. However, this year this influence is expected to be weak. 

Arctic sea ice has started to increase in area now, but is still below the climatological average for the time of year, especially in the Kara Sea. Indications are that this might support the negative NAO conditions described in the paragraph above, although as yet the predictive association is not fully demonstrated. The winds in the equatorial stratosphere are currently strong and westerly, indicating the westerly phase of the Quasi –Biennial Oscillation; this phase typically favours the positive phase of the NAO in winter. This influence is currently only weakly represented in most forecast models. On balance a greater proportion of the drivers that affect UK weather are suggesting a negative NAO winter; indeed, computer models favour higher pressure than normal across the country and blocked atmospheric circulation over the normal eastward moving Atlantic storms. This is reflected in the temperature forecast for December-January-February, with rather colder-than-average outcomes slightly enhanced relative to climatology – as can be seen in figure T2. 

 

Temperature Summary

 

Summary precipitation

 

Confidence in the forecast for precipitation across the UK over the next three months is relatively low. There is a preference for below-average precipitation during December. For the December-January-February period as a whole there is a slight signal for below-average precipitation. The probability that UK precipitation for December-January-February will fall into the driest of our five categories is around 25% 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 discussed in the temperature section, forecast models favour a negative NAO pattern this winter, with high pressure areas more likely to be centred over or close to the UK. As in all seasons, this pre-dominance of anticyclones is likely to lead to drier-than-normal conditions across the country, as can be seen in figure P2 where the forecast shows a shift towards below-average values. The weakening of the prevailing westerly flow means that the normally wetter western or northwestern parts of the country may see a significant reduction in precipitation compared to average, while the east or southeast may be closer to average. However uncertainty in this regional pattern of precipitation is large. With colder-than-normal conditions being favoured, as indicated in the temperature section, the probabilities for precipitation falling as snow and for occurrence of ice this winter will be higher than the climatological values.

 

Precipitation Summary

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and this was their temperature idea 1 month ago

November to January

 

Temperature

 

There is a strong signal in the forecast for above-average November-mean temperatures. For November-December-January above-average temperatures are considered more likely than below, though this signal is likely strongly influenced by the expected mild November. Overall the probability that the UK-mean temperature for November-December-January will be in the warmest of our five categories is close to 30% and the probability that it will fall into the coldest category is approximately 15% (the 1981-2010 probability for each of these categories is 20%).

 

that looks to me like about a 180 degree switch round in the most likely temperature levels!

 

Edited by johnholmes
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I commented in another thread that the science was pointing to a milder, westerly dominated winter but that the accepted theories may be facing a challenge in the future. There have been a few alterations to accepted thinking in recent years: eg variations in the ENSO mode to include the different patterns of Modoki category - whether it is influences from AGW, ice loss or solar changes - some aspects of the circulation patterns are not conforming to what is expected.

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December update issued

 

January to March

 

Summary Temperature

 

Latest predictions for UK-mean temperature favour near or just above average temperatures for both January and January-February-March. Overall, the probability that the UK-mean temperature for January-February-March will fall into the warmest of our five categories is around 20% and the probability of falling into the coldest of our five categories is close to 10% (the 1981-2010 probability for each of these categories is 20%). 

In terms of atmospheric forcing factors which are known to influence UK weather on monthly and seasonal time scales, stratospheric conditions are expected to be the main driver through the rest of this winter. Stratospheric conditions are now in a strong westerly quasi-biennial oscillation (QBO) phase, which has an established link to autumn and wintertime conditions over northwestern Europe, favouring positive North Atlantic Oscillation (NAO). Regarding other drivers, there are currently no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña conditions prevail. In this respect computer models favour a continuation of neutral conditions during the coming months, leaving the influence of this as a forcing factor weak and not expected to contribute predictive value for conditions across Europe during the next three months.

 

Arctic sea ice extent is greater than this time last year but remains a little below the climatological average for the time of year, mainly north of Scandinavia over the Kara Sea. This potentially favours negative NAO but currently the association is weak. There are some signs that a sudden stratospheric warming could occur near the end of winter, allowing surface conditions to change in late winter. While this is an important source of uncertainty in the forecast, it is currently unlikely to occur in the next month and on balance, the more likely outcome for the January-February-March period is near or above average temperature, as can be seen in figure T2. It is important to note, however, that this favoured overall outcome does not of course preclude occasional cold spells.

 

Temperature Summary

 

Summary precipitation

 

Latest predictions for UK-precipitation favour near-to-above-average rainfall during January. For January-February-March as a whole there is a slight signal for near or just above average rainfall. The probability that UK precipitation for January-February-March will fall into the driest of our five categories is around 20% and the probability that it will fall into the wettest category is between 10 and 15% (the 1981-2010 probability for each of these categories is 20%). 

As discussed in the temperature section, some weakening of the prevailing westerly flow through the course of the winter is likely allowing areas of high pressure to be nearer the UK than during much of December 2013. This in turn reduces precipitation, so whilst the January-February-March period as a whole may be slightly wetter than average, as indicated in figure P2, there are signs of February and March being a little drier than average. A weakening of the prevailing westerlies would also affect the distribution of precipitation allowing normally wetter western or northwestern parts of the UK to see the largest reduction in precipitation compared to average, though the uncertainty in this kind of regional detail is large.

 

Note that as snow and ice frequency in winter is more closely related to temperature than total precipitation, the signal for near or just above average precipitation over the January to March period as a whole should not be misinterpreted as meaning near or just above average snowfall. 

Precipitation Summary

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January update issued

 

February to April

 

Summary Temperature

 

Latest predictions for February favour a continuation of the predominately mild conditions experienced so far this winter, with above average temperatures more likely than below average. For February, March, April as a whole, confidence is lower, but temperatures near to slightly above average are most probable. Overall, the probability that the UK mean temperature for February, March, April will fall into the warmest of our five categories is around 20% and the probability of falling into the coldest of our five categories is close to 10% (the 1981-2010 probability for each of these categories is 20%).

 

There are currently no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña prevailing. Computer models suggest near-neutral conditions persisting in the coming months; this will offer little predictive value for conditions across Europe during the next three months. The Quasi-Biennial Oscillation (QBO), an oscillation of the equatorial zonal wind in the stratosphere, continues to be in a westerly phase, although not as strong as earlier in the winter. The QBO does have a link to conditions over western Europe during the winter months, by influencing the strength of the polar vortex and thereby the phase of the North Atlantic Oscillation (NAO). A westerly phase of the QBO tends to favour a stronger polar vortex, leading to a positive phase of the NAO. This is a transitional time of year with the QBO exerting some influence at the beginning of the season but providing little known contribution by the end.

 

During February, the factors described above, along with computer models having a preference for positive NAO conditions, favour a continuation of the predominately mild weather experienced so far this winter. This does not preclude occasional spells of colder weather, but these are less probable than is typical at the end of winter and early spring. The left-hand graph of Figure T2 shows a shift towards milder conditions, with a reduced probability of below-average temperatures and an increased probability of above-average temperatures. As the season progresses the large-scale global drivers become less influential and confidence in predictions for temperatures during February-March-April is lower than for February alone. The right-hand graph of figure T2 reflects this, with the forecast curve more closely resembling climatology than the curve for February. Nevertheless, even with lower confidence, there is still an increased probability of near to above-average temperatures.

 

Temperature Summary

 

Summary precipitation

 

During February, the balance of probabilities suggests a continuation of the very unsettled weather experienced so far this winter, with above-average rainfall most probable. For February-March-April, predictions for rainfall are very uncertain and largely indistinguishable from climatology. The probability that UK precipitation for February-March-April will fall into the wettest of our five categories is between 20 and 25% and the probability of falling into the driest of our five categories is between 15 and 20% (the 1981-2010 probability for each of these categories is 20%). 

The winter season so far has been characterised by a series of Atlantic storms crossing the UK, bringing frequent spells of wet and windy weather. The frequency of heavy rainfall and strong wind events has been higher than in a typical winter. This increased storminess is consistent with the predominately positive phase of the North Atlantic Oscillation (NAO). As discussed in the temperature section, there is a preference in computer models for the positive phase of the NAO to continue in February and therefore conditions to be similar to those experienced so far this winter.

 

The left-hand graph in figure P2 highlights a shift towards above-average rainfall. During February, the pattern of atmospheric circulation which favours above-average precipitation also tends to increase the frequency of Atlantic storms crossing the UK and spells of windy weather may be more frequent than is typical. For February-March-April as a whole, confidence in rainfall predictions is relatively low. At this time of year, large scale global forcing factors become weaker and therefore predictability is lower than in the winter months. The right-hand side graph of figure P2 reflects this, being largely indistinguishable from climatology. 

Precipitation Summary

Edited by Summer Sun

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A bit late but here is the February update

 

March to May

 

Summary Temperature

 

Latest predictions for UK-mean temperature favour near- or above-average temperatures for March-April-May. Overall, the probability that the UK-mean temperature for March-April-May will fall into the warmest of our five categories is around 30% and the probability of falling into the coldest of our five categories is 10% (the 1981-2010 probability for each of these categories is 20%). 

As we move into spring the factors which are known to influence weather conditions over northern Europe, including the UK, are fewer than during late autumn and winter. The Quasi-Biennial Oscillation (QBO) of the equatorial zonal wind in the stratosphere remains in its westerly phase which favours the positive phase of the North Atlantic Oscillation (NAO) and may continue to exert influence on UK weather in late winter and early spring. Meanwhile, the Madden Julian Oscillation is currently in a moderately strong phase over the western Pacific. This phase would favour the negative phase of the NAO over the next few weeks. There remain no significant sea surface temperature anomalies across the tropical Pacific and therefore neither El Niño nor La Niña prevails.

 

Computer models suggest these near-neutral conditions being more likely than not to persist through the spring, leaving this factor unlikely to exert a strong influence on European weather. In spite of apparently competing influences, the weight of computer model output suggests a weak preference for the positive phase of the NAO. Consistent with this, temperatures for March-April-May as a whole are more likely to be above average than below average, as indicated in Figure T2. March-April-May is highly unlikely to be as cold as during 2013.

 

Temperature Summary

 

Summary precipitation

 

Latest predictions for UK precipitation suggest that for March-April-May as a whole the risk of either above- or below-average rainfall is near climatological levels. The probability that UK precipitation for March-April-May will fall into the driest of our five categories is 15% and the probability that it will fall into the wettest category is between 15% and 20% (the 1981-2010 probability for each of these categories is 20%).As discussed in the temperature section no single forcing factor appears dominant, and in view of competing influences little shift from climatology appears in forecast signals. For March-April-May as a whole there is a near climatological risk of both above-average and below-average rainfall, as indicated in the right-hand side graph in Figure P2 where the forecast curve is close to the climatology curve. It is worth noting that as spring progresses the character of rainfall usually changes to convective, showery rainfall becoming dominant in the rainfall distribution. This could lead to potentially marked local variations in amounts. 

Precipitation Summary

 

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March update issued

 

April to June

 

Summary Temperature

 

Latest predictions for UK­ mean temperature favour above ­average temperatures for both April and for April­ May­ June as a whole. Overall, the probability that the UK­ mean temperature for April ­May June will fall into the warmest of our five categories is between 25 and  30% and the probability of falling into the coldest of our five categories is between 5 and 10% (the 1981­2010 probability for each of these  categories is 20%).

 

Although there are currently no significant sea surface temperature  anomalies across the tropical Pacific and so neither El Niño nor La Niña currently prevails, latest observations support model predictions that a  transition to El Niño conditions is more likely than not during the year. At  this stage it is too early for El Niño to exert an influence on European  weather this spring, but should El Niño conditions develop, they will start  to influence global weather patterns later this year.

 

Two factors that do have some potential to influence weather conditions  over the British Isles during April are stratospheric conditions and the  Madden Julian Oscillation (MJO). The final breakdown of the stratospheric  winter vortex, which occurs as the sun begins to heat the Arctic  stratosphere in spring, is likely to occur two to three weeks earlier than  average. This favours a greater chance of blocked weather patterns and  easterly weather types during April. Conversely, the MJO is expected to enter its active phase over the Indian Ocean during early April and this  may favour the positive phase of the North Atlantic Oscillation  developing, although this association is strongest during winter.

 

The ensemble of seasonal forecasts suggests some preference for a higher ­than­ average frequency of blocked weather patterns over the UK during April. This would manifest itself as a greater ­than­ usual incidence  of a broadly easterly weather types and lower­ than ­average frequency of  Atlantic frontal zones progressing across Britain.

 

April is still a period of transition in weather patterns from winter to  summer and forecasting temperatures during easterly weather types can  depend on conditions over continental Europe. Given that North Sea  temperatures are above normal and snow cover across Europe is below  average any easterly flow during April is likely to be less cold than average.

 

Temperature Summary

 

Summary Precipitation

 

Latest predictions for UK precipitation are largely indistinguishable from climatology for both April and April­ May­ June as a whole. The probability that UK precipitation for April­ May­ June will fall into the driest of our five categories is between 10 and 15% and  the probability that it will fall into the wettest category is between 20 and 25% (the 1981­2010 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 challenging to predict given that the  likelihood of localised convective rainfall increasingly dominates the rainfall distribution. 

 

As discussed in the temperature section, at present no single  forcing factor appears dominant. With the weight of the  predictions currently suggesting some preference towards a  blocked pattern for at least part of April, as well as some drift  towards slightly more unsettled conditions developing as the  month progresses, the signal for rainfall amounts over the  month as a whole is largely indistinguishable from climatology.

 

Over the 3­month period, April­ May­ June, the precipitation probabilities are largely indistinguishable from climatology, as indicated by the right­ hand side graph in Figure P2. This means that the probability of the exceptionally wet conditions of April ­May­ June 2012 is currently estimated as very low (note how none of the blue crosses on the right panel of  Figure P2 are as high as the grey cross labelled 2012).

 

Precipitation Summary Apologies for the messy parts of the post unfortunately I can't do anything about it

Edited by Summer Sun
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April update issued

 

May to July

 

Summary Temperature

 

Latest predictions for UK ­mean temperature favour near­ or above­ average temperatures for May; the forecast for May­ June ­July as a  whole is largely indistinguishable from climatology. 12 Overall, the probability that the UK ­mean temperature for May­ June ­July will fall into the warmest of our five categories is around 25%  and the probability of falling into the coldest of our five categories is close to 20% (the 1981­2010 probability for each of these  categories is 20%)

 

Although there are currently no significant sea surface temperature  anomalies across the tropical Pacific, latest observations continue to  support model predictions that a transition to El Niño conditions is  more likely than not later this year. At this stage it is too early for El  Niño to exert an influence on European weather for the rest of this  spring and during early summer, but should El Niño conditions  develop they will start to influence global weather patterns later  this year.

 

Factors that can influence the UK's weather during the late spring  and early summer currently provide no clear indication of likely  dominant weather types during this period. Likewise, computer  model signals are indistinct regarding likely atmospheric circulation types affecting Britain during the coming months.

 

Overall the ensemble forecast shows a weak preference for slightly higher ­than­ average frequency of blocked weather patterns over or near the UK for at least part of late spring and early summer. This  lends some support to the increased likelihood of near ­or above ­average temperatures in May, leaving May 2014 most likely warmer than May 2013 (note how very few of the red crosses on  the left­ hand panel of Figure T2 are as low as the grey cross labelled 2013)

 

Taking the May­ June­ July period as a whole there is very little evidence to separate the forecast temperature distribution from the  climatological distribution, as shown in Figure T2.

 

Temperature Summary

 

Summary Precipitation

 

Latest predictions for UK precipitation are largely indistinguishable from climatology for both May and May ­June­ July as a whole. The probability that UK precipitation for May­ June ­July will fall into the driest of our five categories is between 20% and 25% and the  probability that it will fall into the wettest category is close to 25% (the 1981 2010 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. As discussed in the temperature section, no single forcing  factor appears dominant and at the same time computer  model signals are weak.

 

Given this lack of signal for any particular atmospheric  circulation type, specific regional variation in forecast rainfall  relative to average cannot be predicted. Over the 3­month  period, May­ June ­July, the precipitation probabilities are  largely indistinguishable from climatology, as indicated by the  right­ hand side graph in Figure P2. This means that the  probability of the exceptionally wet conditions of May ­June ­July 2012 are considered low (note how very few of  the blue crosses on the right­ hand panel of Figure P2 are as high as the grey cross labelled 2012). However, late spring  and summer rainfall is often showery in nature so significant  regional variability is often likely.

 

Precipitation Summary

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Quite a while since I last updated this, Septembers update is out now which cover the period of October to December

 

October to December

 

Summary Temperature

 

The latest predictions for UK-mean temperature favour above-average temperatures for both October and October-November-December as a whole. The probability that the UK-mean temperature for October-November-December will fall into the warmest of our five categories is around 35% and the probability of falling into the coldest of our five categories is close to 10% (the 1981-2010 probability for each of these categories is 20%). After returning to nearer normal values during late summer, sea surface temperatures across much of the tropical Pacific, particularly west of the International Date Line, have started warming again. Computer models and expert opinion continue to suggest that there remains a chance of an El Niño event becoming established by the end of the year. A weak event remains then most likely, though there is also a chance that El Niño conditions will not become established at all. Either way, with El Niño conditions not yet established this factor is not expected to exert an influence on weather patterns in Europe during the next three months.

 

Of other potential drivers of large-scale seasonal variability at this time of year it is worth noting that whilst Arctic Sea ice extent is both at its annual minimum and substantially lower than what is climatologically usual, there are no clear indications of its influence on UK weather. Sea surface temperatures remain above average across the western side of the North Atlantic. During early autumn the predicted jet stream intensity and position over the Atlantic leaves the UK a little more likely than usual to be under the influence of areas of high pressure and thus episodes of settled weather. Later in the autumn, computer models show remarkable similarity in showing a transition to a much more cyclonic regime developing across the Atlantic and northwestern Europe from mid-October onwards through November and into December. This suggests a greater frequency of episodes of unsettled weather relative to climatology.

 

As autumn is a transitional time of year, it is worth noting that a given circulation pattern can result in very different temperature outcomes between early and late autumn. For example, settled weather in early October would usually lead to above-average daytime temperatures but a similar pattern in November or December would likely result in colder than average conditions. Conversely, a particularly unsettled weather pattern can also produce very mild conditions, especially by night, from late October. This is particularly so when there are positive sea surface temperature anomalies around British waters, as is currently the case.

 

Consequently, with settled conditions more likely than not early in the forecast period and more unsettled synoptic types considered more likely than not to dominate from later in October, above-average temperatures are favoured

 

Temperature Summary

 

Summary Precipitation

 

The latest predictions for UK precipitation favour near- or above-average rainfall during October and above-average rainfall for October-November-December as a whole. The probability that UK precipitation for October-November-December will fall into the driest of our five categories is around 15% and the probability that it will fall into the wettest category is between 25 and 30% (the 1981-2010 probability for each of these categories is 20%).

 

Autumn marks a shift in character of the precipitation across the UK. In summer it is often convective in nature which can lead to quite large localised variations in accumulations across any given region. In autumn it becomes increasingly dominated by larger scale weather systems driven by Atlantic depressions bringing more periods of widespread rain. At this time of year these depressions can be intense and carry large amounts of moisture making the latter part of autumn and early winter often the stormiest and wettest part of the year. This is all reflected in figure P1 which shows the October-November-December period being, climatologically, the wettest period of the year.

 

As discussed in the temperature section, there is remarkable consistency in computer models’ hemisphere-wide projections for a large part of October, November and December, including an increased frequency of cyclonic weather types affecting the UK. This, in turn, brings an increased risk of episodes of heavy rainfall relative to what is usual for the time of year, and clearly a marked change from the recent period of settled weather. As such wetter-than-average conditions are favoured over drier-than-average

 

Precipitation Summary

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October update issued, above normal temperatures are still favoured

 

November to January

 

Summary Temperature

 

For both November and November-December-January as a whole above-average UK-mean temperatures are more likely than below-average. Overall, the probability that the UK-mean temperature for November-December-January will fall into the warmest of our five categories is around 25% and the probability of falling into the coldest of our five categories is 15% (the 1981-2010 probability for each of these categories is 20%).

 

The whole tropical Pacific Ocean has remained warmer than average for over six months; however, the pattern of sea surface temperatures anomalies and the atmospheric response typically associated with an El Niño – Southern Oscillation event has yet to materialise. During the past month further warming of the central and eastern Pacific has occurred and a weak event remains possible by the end of the year, although there is also a chance that El Niño conditions will not become established at all. With El Niño not yet established, or only weak if it develops, this factor is not expected to exert a significant influence on weather patterns in Europe during the next three months.

 

In the Arctic, sea ice is growing and is a little below average across the basin as a whole. Sea ice extent to the northeast of Russia is well below average, whilst closer to Europe, in the Kara Sea, the extent is close to average for the time of year. There is no clear indication whether these anomalies have a significant influence on weather patterns in the UK. The Quasi-Biennial Oscillation (QBO), an oscillation of the equatorial zonal wind in the stratosphere, is currently changing from a westerly to an easterly phase. In the winter months an easterly phase is typically associated with a weaker polar vortex. A weaker polar vortex can lead to a greater incidence of blocking patterns over the northern hemisphere, which would increase the probability of cold weather across Europe.

 

Despite the apparent lack of strong forcing factors to influence weather patterns, computer models are in good agreement in suggesting a positive phase of the North Atlantic Oscillation (NAO) during the first half of this period. A positive NAO is characterised by an enhancement of the westerly winds across the Atlantic which, during late autumn and early winter, brings above-average temperatures to western Europe. Later in the period, the confidence in the forecast of the NAO reduces, with computer models having a much weaker signal and with it the risk of occasional colder outbreaks increases. However, the overall probability of below-average temperatures is lower than climatology, as can be seen in figure T2.

 

Temperature Summary

 

Summary Precipitation

 

Latest predictions for UK-mean precipitation favour near- or above-average rainfall for November and for the November-December-January period as a whole. The probability that UK precipitation for November-December-January 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 25% (the 1981-2010 probability for each of these categories is 20%).

 

As already mentioned in the temperature section, there is a consistent signal from computer models for a positive phase of the North Atlantic Oscillation (NAO) to dominate, at least during the first half of this period. In a positive phase of the NAO, precipitation is more likely to be above average than below average. Although above-average precipitation is favoured, uncertainty is still large; this is highlighted in figure P2, where there is broad range of outcomes, but also a clear shift towards wetter-than-average conditions.

 

The atmospheric patterns which favour above-average precipitation also tend to increase the frequency of cyclonic weather systems crossing the UK and thus spells of wet and windy weather may be more frequent than is typical, particularly in the early part of the period.

 

Precipitation Summary

Edited by Summer Sun
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This will be interesting! The only way both the MO and the OPI can be accurate is if we only see a cold pattern develop from late Jan and have zonal patterns in December. Otherwise one of them has to be wrong; which one will be correct?

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