Jet Streams: Characteristics and Aviation Impact

050-02-07Pablo Asensio Martínez2026-04-012 min

A Jet Stream is a fast, ribbon-like air current in the upper troposphere.

Jet Stream Globe

General Characteristics

  • Minimum Speed: 60 kt (can exceed 200-300 kt).
  • Direction: Generally from West to East (Westerly), due to the Earth's rotation (Coriolis).
  • Typical Dimensions:
    • Length: Thousands of miles (~1500 NM).
    • Width: Hundreds of miles (~200 NM).
    • Depth: Thousands of feet (~12,000 - 18,000 ft).
    • Height/Width Ratio: 1/100.
  • Cause: Strong horizontal temperature contrasts between two air masses.

Core Location

Jet Cross Section

  • The Jet core is always found in the warm air mass (Tropical).
  • Vertically, it is located:
    • Just below the tropopause of the warm air.
    • Above the tropopause of the cold air.

Main Types

Main Jet Streams Types

1. Polar Front Jet

  • Location: Between the Polar Cell and the Ferrel Cell (over the Polar Front).
  • Altitude: Approx. 30,000 ft.
  • Latitude: Variable (40°N - 60°N), moves south in winter and north in summer.
  • Direction: West (Westerly).

2. Subtropical Jet

  • Location: Between the Ferrel Cell and the Hadley Cell (over the Subtropical Highs).
  • Altitude: Approx. 40,000 ft (200 hPa).
  • Direction: West (Westerly).
  • Characteristics: More constant and permanent than the polar jet.

3. Equatorial Jet

  • Exception: It is an Easterly jet.
  • Seasonal: Only appears in the Northern Hemisphere Summer (Jun-Aug).
  • Location: SE Asia, India, Central Africa (~15°N).
  • Altitude: Very high, FL450 - FL500 (~50,000 ft).

Clear Air Turbulence (CAT)

Turbulence associated with the Jet Stream is caused by strong wind shear (horizontal and vertical).

  • Zone of Greatest Turbulence:
    • On the COLD side (Low Pressure) of the Jet.
    • Just below and to the side of the core axis.
    • In the Northern Hemisphere, it is the North side.
  • Identification on Charts: Areas where isotachs (lines of equal wind speed) are very close together.
  • Visual Signs: Striated or elongated Cirrus clouds (Jet streaks).

Relationship with Temperature (Northern Hemisphere)

If you fly perpendicular to the Jet Stream (from South to North) below the core:

  1. You are in the warm sector (South of the Jet).
  2. You cross into the cold sector (North of the Jet).
  3. The temperature decreases.
  4. The wind (from the West) will come from your left.