I was poking around for weather forecasts and found the Metcheck website which I'd used some years ago and for some reason moved to another.
Interestingly they show this chart
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but although they give units for the colours on the chart it doesn't say what the units are. Can anyone here interpret this chart for me please - it does seem that 'red' is bad !?
You probably hear a lot about the Jet Stream in the news. It's either too f ar North or too far South. The jet stream is identified as winds at 300mb ( during Winter) and 200mb (during Summer). It is these winds which are respo nsible for driving and developing weather systems across the Atlantic.
The images are updated twice a day at 6.10am and 6.10pm (BST) and take appr ox 20 mins to complete."
The isobars on that chart are surface level isobars, the colours represent wind speed in mph of the jetstream at a defined pressure altitude (usually 300mb or around 30000ft)
"Following the adoption of the Pascal as the SI unit of pressure, meteorologists chose the hectopascal as the international unit for measuring atmospheric pressure. (1 hPa = 100 Pascals = 1 mb.) The millibar is still often used in weather reports and forecasts for the public, but the term hectopascal is increasingly being used, especially on the Continent in general and France, in particular. After all, Pascal was a Frenchman!"
I suspect it was close to when June 01 became the first day of summer :-)
On the subject of the jet-stream I have just been reading that the storm coming this weekend will "move the jet-stream"
"They said Bertha, which has moved from a hurricane to a tropical storm, threatens to knock the jet stream out of position, affecting Britain?s weather for weeks."
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However last winters conveyor belt of storms took an unusual track because of the unusual position of the jet-stream.
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"Variations in the jet stream - such as curvature or changes in speed - can drive the development of storms. The faster the jet stream, the greater force behind these variations - and that's meant a conveyor belt of storms coming to the UK."
So I am left asking do storm tracks fix the position the jet-stream or does the jet-stream fix the position the storm tracks?
Here, not outside professional meteorological use. To my knowledge they have been using hPa for at least 25 years in public weather forecasts in Australia, maybe even longer.
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