North Atlantic Upper Shear Increasing Rapidly as TC Season Begins to Fade

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Fig. 1: North Atlantic basin satellite view and current tropical systems.

Fig. 2: Upper shear is increasing rapidly.

Discussion: Sean has been downgraded to a tropical depression in the east-central North Atlantic tropics (Fig. 1). NOAA/NHC indicates this system will travel northwestward without regaining strength into the weekend. A tropical disturbance in the far eastern North Atlantic tropics has a 30% chance of becoming a tropical storm this weekend. The upper shear is increasing and preventing either system from becoming a vigorous tropical cyclone. An area of thunderstorms in the central Gulf of Mexico was unable to become a tropical system this week due to upper shear. However, heavy rain and severe weather affects Florida today as the remains of this system track northeastward. The upper shear into the tropics is increasing spawned by a vigorous U.S. jet stream pattern (Fig. 2).