mandlmaunder
Well-Known Member
Just found a useful site if you are interested in what the Jet Stream is doing over the UK.
http://www.metcheck.com/V40/UK/FREE/jetstream.asp
http://www.metcheck.com/V40/UK/FREE/jetstream.asp
The Jet Stream over Britain
- Thread starter mandlmaunder
- Start date
boatmike
Well-Known Member
Yes it's a good met site generally and good to see the JS moving northwards again. Guess we will now get drier colder weather for Christmas!
Chris_Robb
Well-Known Member
By the 16th December, it shows it racing striaght through the straights of Gibralter and through the Med. Does that mean that there will be dreadfull weather in the Western Med?
KellysEye
Well-Known Member
>racing striaght through the straights of Gibralter and through the Med. Does that mean that there will be dreadfull weather in the Western Med?
There is high pressure over the Med currently and due to hang around until at least the 16th. That should block the low coming in from the west. There again seven day forecasts are invariably wrong.
There is high pressure over the Med currently and due to hang around until at least the 16th. That should block the low coming in from the west. There again seven day forecasts are invariably wrong.
davidej
Well-Known Member
I see from the metcheck website that jetstreams are defined as the winds at 300 mb (winter).
Does this mean the height at which atmospheric pressure 1s 300 millibars. If so what is this approximately in thousands of feet?
Does this mean the height at which atmospheric pressure 1s 300 millibars. If so what is this approximately in thousands of feet?
KellysEye
Well-Known Member
>Does this mean the height at which atmospheric pressure 1s 300 millibars. If so what is this approximately in thousands of feet?
Yes. Thirty thousand feet.
1000 mb-- near surface
850 mb-- 1,500 meters (5,000 feet)
700 mb-- 3,100 meters (10,000 feet)
500 mb-- 5,500 meters (18,000 feet)
300 mb-- 9,300 meters (30,000 feet)
Yes. Thirty thousand feet.
1000 mb-- near surface
850 mb-- 1,500 meters (5,000 feet)
700 mb-- 3,100 meters (10,000 feet)
500 mb-- 5,500 meters (18,000 feet)
300 mb-- 9,300 meters (30,000 feet)
Roberto
Well-Known Member
if you take a typical 300hPa (or mbar) chart like this, the numbers you see are heights (in decametres) where pressure equals 300mb, every single line is drawn through points where computed pressure is 300hPa and height is equal to the number associated with the line (iso-heights)
in this chart the height where one finds 300mb roughly varies from 8400m (NE canada?) to 9600m to the south
The same principle is used in 500hPa, 700hPa charts etc.
The contrary happens with surface charts: height is kept constant (sea level) and lines are drawn connecting points with the same pressure (isobars)
