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Jetstream and L/H patterns

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  • 18-07-2004 1:41pm
    #1
    redspider
    Registered Users Posts: 2,544 ✭✭✭


    As some of you will know, the Jetstream this summer is behaving out of sorts and has been driving a series of continuous Low pressure systems across Ireland and the NW of Europe. The east coast of the US is also experiencing a poor summer weather-wise I believe.

    What would be interesting to see is a view of the trends of Low and High pressures that traverse Ireland throughout the year. For example, an MPEG file if the different Sat images, whether visual wavelength, infra-red or a composite.

    Does anyone have such images/information available or know of a source, or is it a case of installing weather viewing software or getting access to Satellite imagery and building something yourself?

    suggestions/opinions, etc welcome ....


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    #2
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    Yeah we've been unlucky with the jet-stream so far but that said its not been a bad summer so far in the south-east, just not very warm.

    http://www.wunderground.com/global/EU_2xJT_Index.html

    2xeu_jt.gif

    Mike.


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    #3
    redspider
    Registered Users Posts: 2,544 ✭✭✭redspider


    Thanks for that pointer mike65. Its an interesting website. The animation does indeed bring the wind systems and their changing patterns to life.

    However, it doesn't address what I'm looking for! Namely the isobars as they change say daily over a whole year in a movie format. If there were 365 images available I could make that into a "movie" with HTML.

    With such a time series of data, it is possible to observe how the jetstream actually moves the L and H areas across the globe. My first particular area of interest is Ireland and Western Europe.

    The Jetstream is late moving further north this year to an Icelandic Low, Azorean High "normal" position. The late move is not unusual in the sense that it does occur every few years but its status is the main determining factor for the type of summer weather in Ireland, "sunny" south east or not!


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    #4
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    Good news - high pressure ridge building over the next few days.

    Mike.


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    #5
    redspider
    Registered Users Posts: 2,544 ✭✭✭redspider


    :-) .... yes, I saw Evelyn Cusack last night and she has a glint and a smile again !

    However, due to chaos theory, we cant count our chickens yet. In all probablity though, it is most lkely that a High pressure system will be within striking distance of Ireland before August is out, unless St Swithin's rule applies!

    And are the chances of an "indian" summer increased? ie: a late "rising" of the jetstream in early summer and a late "dropping" of it in early autumn?


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    #6
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    Originally posted by redspider
    And are the chances of an "indian" summer increased? ie: a late "rising" of the jetstream in early summer and a late "dropping" of it in early autumn?


    Funny you should ask -

    http://www.weatheronline.co.uk/feature/mo190704.htm
    Our forecast pattern remains on course this week, although computer models are having difficulty resolving exactly when high pressure will start to build into the UK and Ireland, settling the conditions of the past few weeks.

    Indications currently are that high pressure should start to become a more frequent visitor next week, building into the UK, and then collapsing away, as thundery rain moves into Ireland.

    The end of July should see the high pressure take whole for a while, before moving away again to be replaced by a more unsettled spell during the first week of August.

    However, the high should be back later with a fine end to the period.

    Confidence in the forecast at this time is best described as moderate.

    Okay they ain't to sure but it look hopeful that August
    will be pretty decent which may lead into a warm September.

    Mike.


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    #7
    redspider
    Registered Users Posts: 2,544 ✭✭✭redspider


    Here is a useful link:

    http://squall.sfsu.edu/scripts/jet_atl_archloop.html


    They also have current jet stream data for the north atlantic and other
    regions and their maps are animated in loops.

    I checked out last Jul 16-23 and this Jul 16-23 and you can definitely see
    a difference in the weather pattern.

    According to the USA Today Weather folks (and no doubt ohters)
    the jet stream upper atmosphere weather can be modelled and
    forecast and has a direct consequence on ground-level weather.


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    #8
    redspider
    Registered Users Posts: 2,544 ✭✭✭redspider


    Did you see that article on the BBC news stating that the Greenland ice sheet is meltng very rapidly?

    http://news.bbc.co.uk/1/hi/world/europe/3922579.stm

    In places it was melting 1 metre a month! Thats incredible really given the amount of ice that is there and its inherent cool temperature.

    The relation with the Irish weather we are experiencing is that ne recent cold spell we had was a system that was bringing cold air from over Greenland. The weather patterns across the northern hemisphere are connected so I'm wondering is there a link between the Greenlans ice sheet melt and the irregular pattern of the north atlantic jet stream this "summer".

    What do you think?


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    #9
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    Interesting story, the beeb are doing a week on climate change mainly on BBC News 24. The melting of the ice could have an effect I guess as it cools the north Atlantic which in turn might start to cool the air that flows above it which might cause the jet-stream to change course. Notice all the mights!

    Mike.


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    #10
    mike65
    Closed Accounts Posts: 88,978 ✭✭✭✭mike65


    mike65 wrote:


    Okay they ain't to sure but it look hopeful that August
    will be pretty decent which may lead into a warm September.

    Well they got August wrong but my hope for September looks like panning out.

    Mike.


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    #11
    redspider
    Registered Users Posts: 2,544 ✭✭✭redspider


    Yeah, at last in Sept, Ireland experienced a H pressure system that STAYED over the country for a few days and produced cloudless days with the sun shining all day long. This is the only H pressure system that did this for Ireland all summer though. For this to happen there must have been a change in the jetstream. It must have moved North and hence allowed the H pressure to settle.

    I just checked it out and its clear to see.
    Select a start date of 21-Aug, 00Z, loop every 6 hrs.
    See the rotating systems.
    Change the start date to the 01-Sep.
    See how the rotation pattern changes. wow.


    However, the hurricane season has started early and these are also coming our way in a big clockwise look around the north atlantic. Their pattern is also different this year pushing them well into the Gulf of Mexico and so pushing them into Florida. I'm not sure if this is jetstream related or due to other weather patterns, but due to the butterfly effect, one system interacts with all others. The globe has ONE weather system!


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