DEVELOPMENT OF TROPICAL CYCLONES IN RELATION TO CIRCULATION PATTERNS AT THE 200-MILLIBAR LEVEL

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  • 1 National Hurricane Research Project, U.S. Weather Bureau, Miami, Fla.
  • | 2 U.S. Fleet Weather Facility, Miami, Fla.
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Abstract

The 200-mb. flow existing above low-level perturbations at the time of development into tropical storm or hurricane intensity was studied. On the basis of observations in a sample of 40 cases, it is concluded that poleward flow aloft, such as is found in the eastern side of troughs in the westerlies and tropical upper-level cold Lows or in the western side of anticyclones, is more favorable for development of low-level perturbations underneath than equatorward flow. It is also shown that flow aloft with anticyclonic vorticity is more favorable than flow with cyclonic vorticity.

Abstract

The 200-mb. flow existing above low-level perturbations at the time of development into tropical storm or hurricane intensity was studied. On the basis of observations in a sample of 40 cases, it is concluded that poleward flow aloft, such as is found in the eastern side of troughs in the westerlies and tropical upper-level cold Lows or in the western side of anticyclones, is more favorable for development of low-level perturbations underneath than equatorward flow. It is also shown that flow aloft with anticyclonic vorticity is more favorable than flow with cyclonic vorticity.

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