Weather 101:The Jet Stream
Tornadoes,winter storms and even hurricanes - chances are you've heard at least one of those phenomena mentioned in the same sentence with the jet stream.
Here's a meteorology 101 rundown about what the jet stream is all about and the important role it plays in the weather you see every day.
Big Picture
- You Can't See It,But It's Above You: In short,the jet stream is a narrow ribbon of strong winds about 30,000 feet above the ground that flows in a general west-to-east fashion. It helps develop and steer weather systems that affect where we live on the Earth's surface and is also where most commercial jets fly (hence the term).
- Strength Varies:The jet stream is strongest in the cool seasons like fall,winter and spring,because of greater temperature contrasts. It's weakest in the summer,and therefore,has less of an influence in those months when temperatures are hotter everywhere across the United States.
- How Strong? Sometimes we see the strongest winds in a jet stream top 200 mph. Since most commercial planes fly at jet stream level,this can shave off flight time if it's a tailwind,or increase flight time if a headwind.
The narrow ribbon above the ground in this image represents the jet stream about 30,000 feet above the Earth.
In Detail
- It's A Severe Storm,Winter Weather Driver: In general,a stronger jet stream has a greater chance of fueling potent winter storms that deliver snow and ice,or a severe weather outbreak that spawns tornadoes,hail and high winds. That's because a stronger jet stream tips the scales toward more intense low-pressure systems and their associated cold and warm fronts closer to the Earth's surface where we live.
- Hurricanes,Too: The jet stream can help steer and affect the intensity of hurricanes. Sometimes hurricanes can be ripped apart and weakened by the jet stream as they approach the United States in the fall. But on occasion,it can be oriented in an optimal position to help ventilate the hurricane and cause it to intensify,as we saw with Category 5 Michael near Florida in 2018.
- The Jet Can Be Wavy: The jet stream often doesn't flow in a straight line from west to east. You might hear a meteorologist refer to a "trough"or "ridge"in the jet stream. The former term refers to a deep,southward plunge in the jet,like the one in the western U.S. on the map below. Usually to the east (downstream) and west (upstream) of that trough is the ridge part,where the jet rides farther to the north.
- Outcome Of A Trough Vs. Ridge Is Different: The trough tends to be associated with colder weather,while locations under the ridge are warmer. In between those two regimes is where stormy weather often occurs. In the map below,that zone of unsettled weather would be located over the central U.S.,where the stronger jet stream winds are indicated in orange and red.
The basic trough and ridge pattern of a jet stream is shown in this map. Winds in the jet stream are shaded weakest to strongest from blue to green,orange and red. An overlay of white arrows shows the general flow of the jet stream diving south with the trough over the West,and then riding back to the north over the East with the ridge.
More To Know
- Discovery Was A Theory First: As early as 1937 atmospheric scientists believed the jet stream existed,according to the American Meteorological Society.
- World War II Confirmed: It was late in the war when B-29 bombers that could fly above 20,000 feet were used over the Pacific when the jet stream's existence was verified,the AMS says. Forecasts estimated the pilots would encounter strong winds in their high-altitude flights,and that was confirmed when they encountered winds from the west over 190 mph.
Chris Dolce has been a senior digital meteorologist with www.weathernow24.com for nearly 15 years after beginning his career with Weather Now 24 in the early 2000s.
