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The highest air pressure in the UK for over 60 years has been recorded in Wales – in the Mumbles, Gower.

Atmospheric pressure readings were recorded at 1050.5 hectopascals (hPa) on Sunday night – the highest reading since January 1957 in Scotland.

Weather experts said an “incredibly strong” Atlantic jet stream had pushed vast amounts of air over the UK – sending the mercury rising.

It means a spell of settled weather – with some frosty mornings for some.

According to the BBC Weather service, the high pressure system has been driven by winds hitting 238mph (383km/h) over the central Atlantic ocean.

In turn, that has lead to a “pile-up” of air over the British Isles, pushing down on the land mass, with the increase in air pressure.

By comparison – the global average air pressure is 1,013 hPa.

In contrast to the highs – during the recent Storm Brenda, the air pressure slumped to just 939 hPa as the cyclone moved across the north Atlantic.

The highest recorded reading for air pressure at sea level in the UK was in 1902 at Aberdeen, when it hit 1,053.6 hPa – or 31 inches of mercury if you are looking at your old wall barometer.

Source: bbc.com

Starting before Christmas, the atmospheric circulation has changed over Europe with the coldest conditions being located over Balkans at the moment. Bu t what about next?

Analyzing the situation, we try to find clues in order to get an idea of the weather that we should expect for the next fortnight.

 

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The first and very important hint is the expected position of the Azores anticyclone, which is the main system that manages and distributes the cold air over Europe. Having a look at figure 1 we can realize that most of western Europe is highly likely to be under anticyclonic conditions for a prolonged period and only the very north countries (e.g. Scandinavia) will be affected by some cyclonic systems. As a mater of fact, the predicted surface atmospheric pressure for the next fortnight is around 1020 to 1030mb, a forecast that is supported by most of GFS prognostic members, but also by most of ECMWF ones (see graphs for Iberia, Central France, South UK και Norway).

The only unclear point is how north the anticyclone will move. This can be seen in the ensembles of the UK and Norway. The position of the anticyclone is crucial if we want to make a prediction of the exact regions that will be affected by one or more consecutive cold outbreaks in eastern Europe. These cold outbreaks will reach fairly south countries as Balkans and even Greece till at least 13/1/2020.

Figure 1 – GFS ensemble forecast till 14/1/2020

 

 

In the meanwhile, NAO and AO indices seem to drop to slightly negative values highlighting the possibility for weakening any systems in north Atlantic ocean and the southern movement of cold air masses (figure 2).

Figure 2 – Prediction of NAO and ΑΟ indices (www.cpc.ncep.noaa.gov)

 

Finally, in figure 3 a new stratospheric heating is expected in Siberia and eastern Europe, which means that the cold air masses that were established and developed there will released and move southwards to eastern Europe. This is definitely another clue we should take into account.

Σχήμα 3 – Θερμοκρασία στην στάθμη των 10mb (στρατόσφαιρα) όπως προβλέπεται από το GFS στις 6/1/2020.

 

So, concluding for the first fifteen days of January we should expect a quite mild weather in most of western and central Europe. However, cold weather and snow may visit eastern Europe from Italy and to the east and from eastern Scandinavia to Greece.

Definitely, the most of Europe is facing a quite mild and relatively warm, in average, December till now. However, there are hints that the circulation pattern will totally change before Christmas.

The current situation

Consecutive low pressure systems coming from the Atlantic ocean are affecting and will continue affecting the weather of western and northern Europe for the next ten days (so till 20/12/2019). This will not allow any significant cold outbreaks around Europe preserving a fairly mild weather and restricting any weather activity mainly in western and northern Europe (Iberia, eastern Italy, France, the UK and Scandinavia. In the meanwhile, the coldest corner of Europe will be (as usual) only the central and northern parts of Scandinavia.

The lack of of cold outbreaks in Europe is depicted by the temperatures in the stratosphere over the north hemisphere (Figure 1). In particular, it seems that for the next ten days the north pole will be well isolated from the rest of the north hemisphere and will “put away” cold air.

 

Figure 1. Temperature at the level of 10mb as predicted for 19/12/2019 12z.

 

What’s next and the hints

The first tool that we may use for estimating the future situation is the indices NAO and AO. During the last 24 hours, there is a small but maybe significant change of both these indices. AO index appears to drop to negative values around 20/12/2019. Similarly, NAO index decreases to slightly negative vales. Combining this information, we may conclude that according to NAO index, the Atlantic activity will weaken, and according to AO index, a cold outbreak may occur in Europe. However, this will not take place before 20/12/2019.

So, for the last ten days of this December, there is another clue supporting the change of the weather pattern. There have already been a few GFS ensemble members (almost 50% of them) predicting an establishment of an anticyclone over the Scandinavia. If something like that happens, the weather will get quite Christmasy in eastern and maybe southeastern Europe, while Christmas will be fairly dry in west and northwest Europe.

 

Stay tuned till our next article, which will come up once we get more reliable data about the period around C

 

 

Μετά τις 20/12/2019 διαφαίνονται και κάποια σενάρια εγκαθίδρυσης Σκανδιναβικού αντικυκλώνα, όπως φαίνεται και στα προγνωστικά μέλη του GFS για την περιοχή της νότιας Νορβηγίας (σχήμα 2). Πιο συγκεκριμένα, σχεδόν το 50% των μελών αυτή τη στιγμή “βλέπουν” την ανάπτυξη υψηλών πιέσεων στην περιοχή. Αν αυτό συμβεί, τότε θα επιτραπεί σε ψυχρότερες αέριες μάζες από τη Ρωσία να κατέλθουν νοτιότερα.

Mild weather in north and west Europe is coming to an end. Southeast regions will be the warmer european corner for the next ten days.

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While southeast Europe having a taste of autumn spells this week, the western regions enjoy mild weather. This scenery is going to rapidly change starting on 1/11/2019, as massive low pressure systems are expected to be developed and affect such regions turning weather pattern into a semi-wintry one.

In particular, the northwest countries (UK, Scandinavia -mostly western-, northern parts of continental Europe) should face consecutive cyclonic systems following by bands of severe rainfall and strong winds. In north and central parts of Scandinavia it is highly likely that the first significant snowfall episodes will occur even over lower ground regions. The rest of western and northern region of our continent will be affected by shortwave troughs, which will be turning the weather at times into rainy with some snow over mounts (Pyrenee and the Alps). The temperature in all these regions will remain around or below average.

Finally, in the southeast the weather will change into milder and warm for the season. Overcast is expected at times with some rain over western coasts as a result of the west flow regime. African dust transportation episodes may occur here.

 

This autumn is characterised by a very rainy beginning for the northwest of Europe and a dry one of southern regions. Is it going to change? So so… Let’s have a detailed look!

 

The synoptic conditions: The Azores anticyclone presents a trend to move northwards pushing some cold air southwards to the southeast of Europe. Depending on the movement of this anticyclone, this cold air mass may reach the Adriatic sea causing cyclogenesis. The possible low pressure system will affect southeast Europe with heavy rain and some snow over mount tops.

 

The UK: It will remain unstable with periods of heavy rain and strong winds especially in the central and north regions, but also some dry spells. The temperature will remain around average.

Scandinavia: It will turn into rainy with strong winds over the southern regions. In the north it will be a bit drier with some rain at times and possibilities for snow over hills and mountains. The temperature will drop significantly especially in the central and northern parts.

Iberia: No rain at all. Mild in the northern, with some heat air pushing from the south. Hotter in the south with an episode of heat wave.

The central Europe: A transitional zone of unsettled weather at the beginning with some rainfalls and some snow over eastern mountains. It will turn into drier for the rest of this region except for German and northeast of this region (countries close to Russia) with some rain episodes. Significant snow may occur over the Alps. West Italy is included in this zone.

The southeast corner: If the cyclogenesis we talked about takes place, the weather will significantly change with heavy rain in the west coast of Balkans and the southern places. Snow may be observed over northern mountain tops. The rest of Balkans will be affected by rain too, however this storm will focus on the places noted before. East Italy may be included.

 

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Significant weather change is expected in eastern Europe gradually the next days and especially from 10/7/2019 and then with temperature drop and afternoon thunderstorms. In contrast, a new heat wave may affect parts of Iberia and south France.

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In particular, part of cold air masses over Scandinavia and Russia will move southwards affecting central/eastern Europe (from Germany to Switzerland to Greece and Turkey) causing unsettled conditions with severe thunderstorms (increased possibilities for hailstorms) during afternoon/evening). In addition, the temperature will significantly drop to levels around or below average after a prolonged period of increased temperatures. As an exception, central/south Aegean and western Turkey will face dry and windy conditions (NE winds).

The cold air masses will remain over northeastern Europe, being dissipated, causing unsettled conditions with rainfalls at times and possibly strong winds at places. The temperatures will remain around or below average.

Unsettled conditions with (mostly) afternoon/evening thunderstorms may occur in northern Iberia with temperatures around average. In contrast, dry and warm conditions (with a possible heat wave) are expected in central/southern Iberia and southern France with temperatures >38°C.

Finally, in northwest Europe, the weather will remain within the climatological limits with periods of rain and sunny spells.

Europe may face extreme weather conditions and differences from places to places the last week (24-30/6/2019) of this June with a heat wave and heavy thunderstorms.

In particular, we expect a significant heat wave, which will affect Spain, Portugal, France, Germany, eastern/southern of England, Italy and Benelux with temperatures that may reach 34-36°C. However, the temperature may exceed 38-40°C at continental places of northwest Africa, central/eastern Spain and southern/central France. At this places dust advection will take place, but this will not be an extreme episode.

The weather will remain stormy with rain episodes at times in Ireland and western/northern UK. However, some storms may affect the UK as a whole at the end of this period.

For the rest of northern countries the weather is expected around normal with some rain episodes and temperatures around the average.

Unsettled conditions will possibly occur in central/eastern Balkans, continental eastern Europe and southern Alps/north Italy with thunderstorms mainly around afternoons and evenings. The temperatures will fluctuate around normal or below.

Etesians (north east winds) will settle over eastern Greece (Aegean) and western Turkey reaching up to 60km/h over seas some days in this period.

It should be noted that this is an overview of the weather in Europe and it cannot replace any official forecast of individual European countries.

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EUROPE WEATHER OVERVIEW MAP MAY

The weather is going to change dramatically the upcoming week in central and mainly eastern Europe from Sunday (12/5/2019) presenting autumnal traits.

 

In particular, from Sunday and then, the Azores anticyclone will be gradually developed and established in western Europe with a centre over the UK. This will result in better (fair and dry) weather conditions in western Europe with hot for the season temperatures over south and west Iberia (up to 35-37°C).

This situation will push colder arctic air masses to invade north and eastern Europe. Snow will occur in north-central Scandinavia even on lower ground regions, while some snow may be observed over hills/mounts in the northern regions of central/eastern Europe (such as eastern Germany, Poland etc).

Next, the majority of eastern Europe, from Italy and further to the east, will be affected by stormy and colder than average weather with rain at times and afternoon thunderstorms mostly in central and western regions. The most severe weather, where hailstorms may occur, is expected in eastern Italy, western Balkans and possibly regions of northeastern Balkans far from the sea.

The weather will remain fair, dry and hot in Cyprus and eastern Turkey.

 

The weather may completely be reversed from 18/5/2019 and then with a possible heat wave in southeastern Europe and rainy weather for the western.

 

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EUROPE WEATHER OVERVIEW MAP MAY

 

 

Stormy weather for southern, slightly cold at south east, mostly dry in the north. This is an overview of the weather in Europe around the Catholic Easter (20-22/4/2019).

 

The driest conditions should be expected in central-southern UK, around North Sea, southern Scandinavia and central-northeaster Europe with temperatures up to 17-20°C. Dry weather in the Aegean Sea, a bit cloudy (chances for short/light showers) in northern Crete on Saturday (20/4/2019) with temperatures between 14-17°C.

The weather will be normally rainy and windy at times in Scotland, northern Ireland, Iceland and northern Scandinavia, with a possibility for some snow over mounts of the very north of Scandinavia. The temperature will not exceed 10-12°C.

Convective weather will dominate in Iberia, southern France and eastern-southern Balkans with thunderstorms or showers mainly in the afternoon. However, on Monday storms will expand over Italy and Adriatic, where rainy/stormy conditions will occur. The temperature ~15-20°C.

The weather will be colder in Turkey and Cyprus and the rest of southeastern Mediterranean Sea with rain and snow over mounts. The temperature around 8°C in Turkey, not higher than 15-17°C in southern.

 

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At least nine people have been killed by flash floods in Rio de Janeiro.

The mayor has declared a crisis after the Brazilian city was battered by heavy rain on Monday and Tuesday.

More than 31cm of rain (13 inches) fell in some parts of the city within 24 hours, the mayor’s office said.

 

 

According to Globo TV, 245mm of rain were recorded within just a few hours in Copa Cabana, while the April precipitation average does not exceed 95mm.

 

The satellite images from MODIS-TERRA below show the extremely low-speed movement of the cloud zone that affected the region. This slow movement was one of the most important reasons of this natural disaster.

 

On the maps below showing the condition on Sunday 7/4/2019 (2100 UTC). In the first map, the shallow low pressure system causes a precipitation zone, which is collocated with the cloud zone in the satellite. In the second map, the CAPE index is fairly enhanced causing eventually a quite unstable regime, ideal for the formation of storms.

 

 

Source: MSN