A Parametric Model for Predicting Hurricane Rainfall

September 01, 2007
  • Contributors:

    Manuel Lonfat, Robert Rogers, Timothy Marchok, Frank D. Marks, Jr.
  • Topic:

    Reinsurance

Monthly Weather Review

This paper explores simple techniques to improve rainfall predictions from the rainfall climatology and persistence model (R-CLIPER), which is used operationally in the Atlantic Ocean basin to forecast rainfall accumulations. The R-CLIPER model creates a symmetric swath of rainfall sensitive to the storm track, speed, and intensity.

The authors enhance the model capability by accounting for the effect of vertical shear and topography on the magnitude and distribution of rainfall produced in landfalling tropical cyclones. Effects modeled in R-CLIPER and those from shear and topography are combined in a new model called the Parametric Hurricane Rainfall Model (PHRaM).

Comparisons of rainfall accumulations predicted from the operational R-CLIPER model, PHRaM and radar-derived observations show some improvement in the spatial distribution and amplitude of rainfall when shear is accounted for and significant improvements when both shear and topography are modeled.

Despite the improvements described above, many processes are not yet represented in the model. Most significantly, we need to address the enhancement of rainfall due to flow convergence along the coasts, the cross-track shift in the rainfall distribution during extratropical transition (ET), and extreme accumulations of rainfall in rainband echoes over specific regions a few hundred kilometers from the storm center.



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