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TROPICAL STORM AND TROUGH INFLUENCE

METEOROLOGIST JEFF HABY

A tropical system or hurricane will be influenced by the position of the mid-latitude trough as the tropical system moves into higher latitudes. The winds of a mid-latitude trough are typically going in the opposite direction that the tropical system is moving since the tropical system is propagated typically by the tropical easterlies. The closer the tropical system gets to a mid-latitude trough, the more it will be deflected from moving toward the west to moving more toward the north. When the tropical system moves into a high enough latitude it can be absorbed and propagated right along with the mid-latitude jet stream.

The diagram below show a tropical system marked as S moving toward a mid-latitude trough. Note that as the tropical system gets closer to the trough it is deflected more toward the north and then deflected toward the northeast. Thus, jet-stream troughs have a significant influence on the motion of a tropical system when it moves into the mid-latitudes closer to the mid-latitude trough.