50 02 Upper Winds And Jet Streams

Question 1

How fast do winds need to be to be classified as a Jet Stream and how fast do they need to be to be featured on a significant weather chart?

Answer 1

• 60kts

- 80kts

Question 2

Name the different global Jet Streams and give their avg. latitudes for Jan and July.

Answer 2

• Arctic Front: Jan ~ 60N to 70N
• Polar Front: Jan ~ 50N, July ~ 60N
• Sub-Tropical Front: Jan ~ 30N, July ~ 40N
• Tropical Easterly
• Sub-Tropical Front: Jan ~ 40S, July ~ 30S
• Polar Front: Jan ~ 50S, July ~ 50S

Question 3

Why does the Tropical Easterly Jet Stream travel west?

Answer 3

There is large amounts of land mass to the north and mostly sea to the south. Air is generally cooler over the sea and so due to Byes Ballast law the wind travels west.

Question 4

Where do Jet Streams form on a front and give details about the conditions?

Answer 4

• Jet streams form when a cold air mass and a warm air mass meet
• They form below the Tropopause in the warm air
• The worst CAT (clear air turbulence) occurs in the warm air, on the cold air side of the jet stream. This is where the greatest pressure gradient is

Question 5

What are the avg. dimensions of a Jet Stream?

Answer 5

• Length: 2000nm
• Width: 200nm
• Height: 2nm

Question 6

In a polar front depression, where (in relation to the surface) do Jet streams form?

Answer 6

• 200nm behind the cold front on the surface

- 400nm in front of the warm front on the surface

Question 7

What are the typical heights of the different Jet Streams?

Answer 7

• Arctic Jet Streams: 20,000ft
• Polar Jet Streams: 30,000ft
• Sub-Tropical Jet Streams: 40,000ft
• Equatorial Jet Streams: 50,000ft

Question 8

With regards to pressure gradients and temperature gradients, where does the core of a jet stream form?

Answer 8

• Highest pressure gradient

- Zero temperature gradient