If the cold air mass is not so strong, its invasion into the center part of a wintertime tropical cyclone strengthens the tropical cyclones.

浅薄冷空气的入侵对热带气旋起加强作用，但强冷空气侵入热带气旋则容易使其减弱消亡。

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That is due, in part, to the presence of a cool and dry air mass to the north and west of the tropical storm, said CNN meteorologist Sean Morris.

CNN: Tropical Storm Alberto forms in the Atlantic