Continue below for the in depth forecast and explanation of the factors which are expected to influence the weather this Summer.
May closes unseasonably cool and showery, conditions which look to spill over into the first day or two of June. Showers remaining a threat through the Jubilee Bank Holiday and following weekend, particularly in the south, but it will turn warmer, while high pressure looks to build in across the north – bringing drier and sunnier weather.
The Madden-Julian Oscillation (MJO) is currently in phase 6 in the Western Pacific and is then expected to progress through phases 7 and 8 through to June 10th or thereabouts before collapsing into the Circle of Death (COD). A propagation through phases 6-7-8 will likely keep weather and temperatures in an up and down transient pattern, preventing long stretches of above or below average temperatures and rainfall for the first half of the month, and most likely not too far removed from either side of normal.
After a fairly dry and settled first weekend in the north, still a showery threat for the south, the second week of June looks to turn more unsettled off the Atlantic across all parts. This tying in with the MJO moving through 7 to 8 – which promotes lower heights / low pressure to the northwest. However, with winds from the south or southwest, temperatures look to be average in the north to slightly above in the south. Most rain falling in the north and west, drier toward the southeast.
As the MJO wave collapses back into the COD on or around June 10th for the remainder of June, so we may see a less changeable pattern develop with more of a longer stretch of the same weather pattern entrenched for the second half of June. High pressure looks like becoming a more dominant and persistent feature over mainland Europe with lower pressure to the northwest over the Atlantic during the second half of the month, most rainfall towards the northwest, drier towards the southeast. The flow generally from the south or a long way to southwest. This is a warmish pattern - with temperatures likely to rise to be slightly above average overall, with potential for brief spells of hot weather in the south taking temperatures more above average - as winds back southerly for a time.
Temperatures overall for the month around or just above average, perhaps as much as 1C above the 1981-2010 long-term average overall, though more above in the south with hotter spells later in the month, perhaps by 2C, than in the north. Rainfall will likely be below average towards the southeast, average towards the northwest closer to low pressure to the northwest, occasional fronts may make progress all parts.
A mixed month appears more likely than not, some warm or hot spells possible, especially the south, but not prolonged. Some unsettled conditions too, as the jet stream dips south over NW Europe at times. Overall, slightly warmer than average, rainfall average. A month away and the MJO uses its usefulness as tool, being too difficult to predict with much confidence that far out. So, I will rely more on analogs of months that fit with the current La Nina status and, also, seasonal modelling.
July looks to start off with low pressure to north and northwest with the jet stream close to northern areas, high pressure close to the southeast over the near continent, this persisting for the first week. Rain mostly likely in the north and west, drier towards the southeast. Then high pressure looks to build northeast during the second week - as the jet stream retreats to the northwest, bringing dry and warm or hot conditions across many areas, this persisting through to mid-month but perhaps until the last third. Then perhaps a change to more unsettled and cooler conditions during the third week as the jet stream sinks south over the UK, with areas of low pressure moving in off the Atlantic crossing the north. Fourth week seeing low pressure retreat southeast over the near continent and high pressure building to the northwest, with northerly or northeasterly winds, lending to a cooler end to the month.
Temperatures slightly above the 1981-2010 long-term average overall - thanks to warmth in the first two thirds of the month, highest temperature anomalies in the south, closer to average in the north. Rainfall around average generally, but perhaps below for the southeast.
Looking an unsettled month overall, with the jet stream often close or over the UK and low pressure more-often-than-not in charge, lows moving east across or close to the north of the UK at times. Ridges of high pressure making brief visits, bringing some drier days here and there. The first half of the month will be unsettled and cool at times with westerly or southwesterly winds and lows moving east bringing rain at times. But some drier days between low pressure systems.
In the second half of the month, with an active hurricane season forecast August onwards, we may see the tail-end of one or two ex-tropical storms or ex hurricanes passing the northwest of Britain, bringing windier conditions and large rainfall totals to western Scotland and perhaps Cumbria - with a risk of flooding. Though these systems may drag brief hot spells north across England and Wales too.
Overall temperatures will be around the 1981-2010 long-term average. Rainfall around average, though with Scotland and parts of the northwest perhaps above or well above average.
The forecast for March was for the month's temperatures to be around average to 1C above overall. Rainfall amounts around average, though with the northwest seeing above average rainfall and the southeast below average. The provisional UK mean temperature was 6.7°C, which is 1.0°C above the 1991-2020 long-term average. Most areas had less rainfall than average. So, our forecast was close on temperatures, suggesting up to 1C above average, but it turned out drier than expected across large areas of the UK.
The forecast for April temperatures was overall for the month likely to be around average, rainfall slightly above average. The provisional UK mean temperature was 8.1°cC, which is 0.2°C above the 1991-2020 long-term average. Most areas had less rainfall than average, The UK overall had 68% of average rainfall, though Scotland and N. Ireland generally had above average rainfall, while much of England had less than half, parts of the east less than a quarter the average. So, again, our forecast for April was close for average temperatures, but it turned out drier than expected for the UK overall.
The forecast for a warm May with temperatures above average overall - perhaps by up to 2°C, average to slightly above average rainfall. Provisional temperatures up to the 30th indicate overall UK temperature for the month was around 1.3C above average. Rainfall was around average. So, our forecast was fairly close for May.
Producing a summer forecast is more challenging than producing one for winter, with less global atmospheric drivers that influence weather patterns than during the winter. In April 2009 the UK Met Office issued their now infamous forecast: "odds-on for a BBQ summer". By the end of August, total precipitation since June had climbed to 42% above the 1971-2000 average.13 years on and perhaps there may be some advances in seasonal forecasting, though predicting rainfall over a season is more prone to error than temperature. Global temperatures are rising due to climate change, so it is perhaps no surprise when a seasonal forecast goes with above average temperatures. Rainfall more susceptible to local scale short-term changes and regional variations, particularly in summer, when localised convective rainfall events can make a difference.
When looking at longer term forecasts for a season, using initial conditions still matters. Though large scale phenomena that happen over long periods of time can be quite a reliable predictor to how the atmosphere and thus our weather patterns can be driven and play out over long periods. Ocean temperatures which can impact global weather patterns, such as El Niño Southern Oscillation (ENSO, tend to change very slowly, so can be a useful predictive tool over longer periods and this one of the main drivers looked at when making this summer forecast.
For winter forecasts the Quasi-Biennial Oscillation (QBO), state of polar vortex and solar cycle, that generally change slowly over long periods, are additional useful predictive tools that tend not to influence summer patterns. But there are also supercomputers, that take all global atmospheric drivers into account. Their numerical predictions and their range of ensembles can predict outcomes by starting with slightly different initial conditions - which can give a broad clue to how weather patterns will play out over a season. Then there is looking at past weather by using analogs of months or seasons that had similar patterns, such as La Nina or El Nino.
There is a range of seasonal models available for the JJA (June/July/August) period. However, given the charts for pressure, temperature, etc they produce cover 3 months, it hides variations during the 3 months. But all the seasonal output indicates above average temperatures for the UK for the JJA period, while the rainfall overall looks below average.
View the multi-model seasonal forecast charts on Copernicus
The phase of El Niño Southern Oscillation (ENSO) that drives tropical weather patterns can also have some influence on the extra-tropical weather patterns at higher latitudes by forcing large-scale patterns across the globe. It is forecast that La Nina will persist through the summer, currently the ONI (Oceanic Nino Index) is -1.0C but recent ENSO SST forecasts, see below, weaken La Nina through the summer.
NOAA's Climate Prediction Center (CPC) thinks La Niña is likely to continue through the end of the year, which would make 3 consecutive autumn -winter seasons with La Niña conditions (last occurrence 1998-2001). ENSO is not the only driving force of weather patterns over a season, while climate change is likely making changes to weather patterns that distort the view given by analogs of past summer months with La Nina background.
Sea surface temperature anomalies are most apparent in the ENSO region, as discussed, characterised by the cool anomalies of La Nina across the tropical Pacific basin. Elsewhere, there are warm anomalies widespread in the North Atlantic, away from the far NW Atlantic, these warm waters may portend to a greater chance of warmer than average conditions for western Europe downstream. Another area of anomalies is the Indian Ocean Dipole (IOD), which like the ENSO, can impact global weather patterns - though to a lesser extent than ENSO. For example, an unusually strongly positive IOD in summer 2019 was linked to drought in Australia and Indonesia, above normal rainfall in East Africa, heatwaves and drought in southern Europe. The opposite extremes of drought or flood tends to happen with a negative IOD. The IOD index has dipped below negative thresholds (0.4°C) during May. The latest IOD index value for the week ending 22 May 2022 was -0.55°C. International climate models indicate a negative IOD event could develop in the coming months, with several forecasting strong negative values of the IOD index by August.
Although the MJO is a wave of enhanced convection that circum-navigates the global tropics, it does impact the upper patterns at higher latitudes of the northern hemisphere, so is a useful tool to use for predictions for 3-4 weeks ahead, but no more than that really. So the June forecast will rely heavily on the MJO event currently forecast to move from phase 6 through to phase 8 before declining in this phase or phase 1 around June 10th.
This summer will be the third consecutive year with La Nina present for at least part of these years. The last time this happened was 1998-2001. As such, 1999 and 2000 are one of the top three analog years, along with 2011, that will be used for predicting what patterns may be in store for this summer. Indeed, as mentioned, SSTs anomalies over the North Pacific and North Atlantic at the beginning of the summers of these years are close match too, as can be seen with the SST maps for the start of summer in those years below against the current SST map.
Current SST Anomalies
Top Analog Year 1: 1999
Top Analog Year 2: 2000
Top Analog Year 3: 2011
I ran monthly climate composites for weak La Nina summer months following moderate La Nina winter months, such as the past winter, since the early 1990s, since when global temperatures have increased rapidly, bearing in mind a for forecast weak La Nina (ONI of -0.5C to -0.9C) to continue this summer. I used the excellent NOAA Physical Sciences Laboratory Plotting page. The best fit analog years of 1999, 2000, 2011 are displayed below as 500mb height plots for each summer month of those 3 years.
For June it suggests low pressure close to the west and southwest, higher pressure over the near continent and NE Europe. This suggests unsettled conditions at times overall, but generally warm towards the southeast, more average towards the northwest. However, for June I will base the forecast more heavily on the MJO composites for phases expected through the month.
Composites of weak La Nina during summer following moderate La Nina winters will be used more heavily for July and August blended with model seasonal forecasts. So for July, the 500mb plots show an emphasis for blocking high pressure to the northwest, centred around Iceland in the means, with lower heights over mainland Europe. For August, lower heights over NW Europe, higher heights over southern Europe.
Summers in general are getting warmer in the last 20 years, with greater incidences of long spells of hot and dry weather. 2019 and 2020 summers are testament to this, with new high temperature records set. The UK's record high was broken with 38.7°C at Cambridge in July 2019. Then in July 2020, 37.8°C was recorded at Heathrow on the 31st, the third highest UK temperature ever recorded.
These warmer summers are part of a trend across much of Europe too, with some exceptional heatwaves. Two large-scale heat waves occurred in late June and July 2019. The late June heatwave set a new record for the European-average June temperature. The most extreme daily maximum 2-m air temperature (t2m) was recorded on 28 June near the city of Nimes (Verargues; 46°C) in France, where a new all-time national record for France was established. The July heatwave resulted in record-breaking temperatures in central and northern Europe. For example, the historical record of Paris was broken by more than 2°C (42.6°C), Belgium and the Netherlands for the first time surpassed the 40°C mark, and new national records were set in Germany, Luxembourg, and the United Kingdom.
So old analogs, particularly older than 30 years ago, can be distorted and lose usefulness as a guide with the background warming with climate change. All ten of the warmest years in the UK have occurred since 1990 with the nine warmest occurring since 2002. So, one would expect a good chance of heatwaves this summer across parts of Europe, given La Nina favours drier more blocked weather patterns. Perhaps not record breaking, but the bar is set high, so any heatwave could have serious consequences for infrastructure and people's health, particularly with a background of dry conditions or prolonged drought -as soil moisture deficit can increase temperatures. Recent summer heatwaves may corresponded with a shift north of the Hadley Cell - pushing the jet stream further north allowing a strong Azores high while also allowing extreme heat from NW Africa to push into Iberia. Weaker jet stream and more slow-moving and blocked troughs and ridge patterns exacerbating these heat domes. Some of this heat may even affect the UK at times too, but often the UK is on the NW periphery of such extreme heat.
Although Hurricanes don't directly affect the U.K., they can have impacts on weather patterns downstream over NW Europe later in the summer. The Atlantic hurricane season - which runs from June to November - is forecast to most likely be above average for tropical cyclone activity according to the latest seasonal prediction from the Met Office.
Hurricanes in the North Atlantic generally occur between late summer and late autumn especially the months of August, September and October. When tropical storms move northeast over the North Atlantic their eventual interaction with the jet stream can have impacts on the weather patterns downstream over western Europe. When the tropical storms interact with the jet stream an become extra-tropical depressions, the transfer of tropical energy can make the jet stream stronger - which can have impacts on the weather over Europe. This can either manifest in a strong ridge of high pressure building downstream over mainland Europe, bringing very warm or hot conditions to western Europe if the jet stream is, as often the case, running northeast over far NW Europe, though Scotland may be wet and windy. But if the jet stream is running more west to east, it can direct wet and windy weather towards the UK. However, interactions of tropical storms on extra-tropical weather patterns over the far north Atlantic and Europe do increase uncertainty. But an active hurricane season can indicate very warm weather for the southeast but possibly wet weather for the northwest in late August for the UK - when the hurricane season starts to pick up.
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