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Winter 2019/2020 - General Discussion
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nacho libre wrote: »It's strange that not many long range forecast are going for a cold spring. I suppose one positive of the strong polar vortex, is that if we do get a favourable pattern change, all that cold could come our way.
I think we will see a a change to something much colder sometime in February. In the mean time if we do manage to get a brief northwesterly airflow it could be quite potent given the record cold up in Greenland
My pet theory is that with cold air tending to be 'locked up' away in the Arctic this year, that this will eventually 'unleash' into the mid latitudes during the Spring as the PV eventually breaks down as it traditionally does in that late-winter/early spring period. What effect this would have is another thing. A cold Arctic blast into the the N. Atlantic could well force much warmer air from the tropics over western Europe; or alternatively, an Arctic blast over the eastern N. American continent could power up the Atlantic and bring us much rain. Or maybe, just maybe, this cold air will come down over us and bring us a repeat of April 1917.
Or, as is more likely, I could be just talking bollox.New Moon
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We can only dream. I am probably in the minority here, but i would love an extreme event like that. At least for those who wouldn't welcome it, they'd not have to worry about several ice days after it!Or maybe, just maybe, this cold air will come down over us and bring us a repeat of April 1917.0 -
Or maybe, just maybe, this cold air will come down over us and bring us a repeat of April 1917.
I had to Google it....
"Strabane, 12 April 1917 - There has not been as cold a spring in Ireland since records began, according to a British meteorologist, Dr Mill.
Ireland is currently in the midst of a brutal spell of April weather. Frost is playing havoc with crops - snowfalls around Dublin are heavy and frequent. Sheep have perished and, in Ulster, a girl living five miles from Strabane was said to have become ‘insane’ after she lost her way in a blizzard and wandered in the fields all night.
Trains have been forced to stop running in various parts after the snowfall was too deep to plough through. There is no likelihood that conditions will ease in the coming days."
https://www.rte.ie/centuryireland/index.php/articles/coldest-irish-april-for-36-years
Sounds great!0 -
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Say my name wrote: »Can anyone say with reasonable certainty what's causing our current high pressure readings?
Say you get a powerful storm here. A strong jet stream and large temperature difference between a cold and warm air mass colliding, could be blamed.
And given that high pressure is the result of cold air descending from high up in our atmosphere and we get these high pressure records in this part of the world in January. Is this the result of a stable polar vortex building up very low temperatures high up in the atmosphere and with the angle of the Sun on the planet this time of year in the northern hemisphere and allowing this cold air to build that it just finds a home in a high pressure system in the nh which atm just happens to be over us atm?
Or is this too simplistic of an explanation?
Thoughts. Reasons?
Could be something to do with that alright, but I am in no position to say. Low pressure to the north means that air is rising rapidly but this air will descend again creating large high pressure zones, such as the current one, to its south. That is how it normally works anyway.
Just looking at stratospheric temps, and at 10 hPa, there does seem to be a pretty anomalous warm region right above the current anticyclone which may well be driving it also?
Don't know how or why, but I'll leave that to bigger brains than I.New Moon
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Say my name wrote: »Can anyone say with reasonable certainty what's causing our current high pressure readings?
Say you get a powerful storm here. A strong jet stream and large temperature difference between a cold and warm air mass colliding, could be blamed.
And given that high pressure is the result of cold air descending from high up in our atmosphere and we get these high pressure records in this part of the world in January. Is this the result of a stable polar vortex building up very low temperatures high up in the atmosphere and with the angle of the Sun on the planet this time of year in the northern hemisphere and allowing this cold air to build that it just finds a home in a high pressure system in the nh which atm just happens to be over us atm?
Or is this too simplistic of an explanation?
Thoughts. Reasons?
Good explanation here from the Met Office.
https://twitter.com/MetOffice_Sci/status/1219302106554757124?s=20
And from Stephen Burt, a visiting fellow at Reading University's department of meteorology talking to the BBC.
"The reason for the extremely high pressure can be traced back to the rapid development of an intense low-pressure area off the eastern seaboard of the United States a few days previously (this is the storm that dumped around 75cm of snow in Newfoundland)," he explained.
"In simple terms, the air drawn out from this system through the actions of a strong jet stream has to be redistributed elsewhere.
"Normally, this would happen over a much larger area of the North Atlantic, leading to the rapid development of a fairly intense anticyclone, which is not uncommon. On this occasion, the 'excess air' (if we may call it that) could only be redistributed over a small area because of the existence of a number of other depressions, resulting in the rapid development and intensification of an anticyclone over the British Isles."
Compare the two charts below and try to spot the differences.
The first is a forecast made 72 hours (three days) ahead; the second one is the actual analysis for the same time, at midnight Sunday into Monday. This is the power of modern numerical models.
"It's remarkable that the models can accurately predict a 1-in-90 year event days ahead, not just 'day-to-day' weather," Mr Burt remarked. "At the time the 72-hour forecast was made, the high had not even begun to form!" he told BBC News.
The 72-hour look ahead
Analysis at midnight into Monday
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