We have already discussed what jet streaks are and how motion works in straight flow. In case you missed it, you can get caught up by clicking on the following link.
In this second part of our discussion on jet streaks, we will discuss what type of motion occurs when a jet streak passes through a trough or ridge axis.
2 Quadrant Jet Streak Model (Curved Flow)
When a jet streak takes on curvature, two dominant quadrants take over.
In cyclonic curvature (trough), the left entrance and left exit become dominant. The left entrance as mentioned above features an area of convergence and therefore sinking motion. The left exit region features an area of divergence and therefore rising motion.
In anticyclonic curvature (ridge), the right entrance and right exit regions become dominant. The right entrance region features diverging air that creates lift. The right exit region features converging air with corresponding sinking motion.
Jet Streaks and Severe Weather
Jet streaks can be important in producing severe weather across the area. They can help strengthen the storm systems by providing an area of enhanced upper level divergence. This increases the lift at the surface thereby strengthening the low pressure in the process. The stronger the low pressure at the surface, the nastier the severe weather associated with it tends to be.
The rising air also supplies the storm system with plenty of warm air aloft. As the warm air rises, it is picked up by the upper level winds and carried further downstream. This warm air out ahead of the storm system helps to increase the temperature gradient. The strong difference in the temperatures allow the fronts at the surface to grow stronger as well. Stronger fronts create a stronger storm system.
Which Jet Streak Curvature Cause the Greatest Amount of Lift?
The strongest lift in jet streak curvature occurs in a cyclonically curved flow. The weakest amount of lift typically occurs in a zonal (straight flow) jet streak. The cyclonic curvature imparts more lift to the jet streak due to an increase in atmospheric spin or vorticity (another topic for another time).
If you are still confused on how jet steaks affect our weather, don’t worry. Jet streak dynamics are confusing to many meteorologists still, and it’s our job to know the weather!
Hopefully this two part series helped to shed some light on why jet streaks create lift and how they can impact our weather.