Tropical Storm Risk (TSR)

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Storm Tracker Documents: Wind Fields

The TSR wind fields are derived from a relatively simple model and are based on limited available data. Although we believe the gross wind field distributions are accurate, the actual wind at a particular location may differ significantly from that shown. Since the TSR site has no official status, the wind fields must not be used to make life or death decisions or decisions concerning the protection of property. Please see the TSR Storm Tracker disclaimer for a list of official agencies whose advice should be sought in such cases.

  When modelled wind fields are available
Wind field modelling is only performed in situations where the Holland Wind Model (see below) applies. Specifically this means that modelling may NOT be applied in the following circumstances:
  • The system maximum sustained wind is below 64 knots (Cat 1 hurricane strength).
  • The system is identified as being extratropical or is undergoing extratropical transition.
  • The translational motion of the system exceeds 15 knots.
The modelled wind fields are also quality controlled. In cases where the actual TC wind field is highly asymmetric the differences between the data and the model can be large. In such cases a wind field is not displayed.
The minimum wind speed displayed in the wind fields is 30 knots.
  Wind field model and data

The modelled wind fields presented by the TSR Storm Tracker are derived by fitting the well known Holland Wind Model for hurricane wind profiles (Holland, G. J., 1980: An analytic model of the wind and pressure profiles in hurricanes. Monthly Weather Review, 108, 1212-1218) to the wind distribution data provided in the tropical cyclone warnings by TPC/NHC, CPHC and JTWC (see data document for more information on TC warnings). The modelling method used by TSR also includes the cyclone translational motion which accounts for the asymmetry in wind field about the storm centre track observed in most modelled systems.

The TC warnings give the minumum distance from the cyclone centre to a given set of wind values in each quadrant (NW, SW, SE and NE) for current and forecast cyclone locations. In TPC/NHC and CPHC warnings these wind values are 34 knots, 50 knots and 64 knots. In JTWC warnings they are 34 knots, 50 knots and 64 knots. A maximum of twelve wind values at different points are therefore available.



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Researched and Developed by Mark Saunders and Frank Roberts
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