On the PredictWind website, PredictWind App and Offshore App, we use many acronyms, codes and symbols. This article will help you understand what they all mean.

WEATHER MODELS:

Please see the article https://help.predictwind.com/en/articles/2884560-what-does-pwg-pwe-gfs-ecmwf-spire-ukmo-hrrr-nam-arome-stand-for for a detailed explanation of each model, how it is produced and what resolution it offers.

  • PWG: The PredictWind proprietary weather model that uses the NCEP global initial conditions

  • PWE: The PredictWind proprietary weather model that uses the ECMWF global initial conditions.

  • GFS: The Global Forecast System from NCEP.

  • ECMWF: The global Forecast model from the European Center for Medium-Range Weather Forecasts.

  • SPIRE: A global forecast model from the company SPIRE

  • UKMO: Also known as the “Unified Model” is the global forecast from the UK Meteorological Office

  • HRRR: High-Resolution Rapid Refresh from NOAA

  • NAM: North American Mesoscale Forecast System

  • AROME: A small-scale numerical prediction model, operational at Meteo-France

WEATHER ROUTING:

TWS = True Wind Speed
TWD = True Wind Direction
TWA = True Wind Angle - the angle of the boat to the wind
SOG = Speed over Ground - includes current forecast
COG = Course over Ground to the next waypoint

TWS Scale Factor = True Wind Speed Scale Factor (see more detail below)

TWD Adjustment = True Wind Direction Adjustment (see more detail below)

TWS Scale Factor - True Wind Speed Scale Factor applies a scale factor to the Wind speeds used for weather routing. This is useful if the forecasts generally predict higher or lower wind speeds than the onboard wind gear. This is a percentage, so as an example, setting it at 95% means you believe the actual wind speed is 5% less than the forecasts.

TWD Adjustment - True Wind Direction Adjustment applies an adjustment to the Wind Direction used in weather routing. This is useful if the forecasts generally predict an offset wind direction compared with the onboard wind gear. This is a change in degrees, so as an example, setting it to -5 means you believe the actual wind direction is 5 degrees more to port. The TWD adjustment is rarely used by top navigators, so we do not recommend changing this value.

The TWD adjustment and TWS scale factor are predominately racing navigator tools, running several weather routes a day during a race with well-calibrated wind instrumentation.

Tack/Gybe Penalties - The tack/ gybe penalty is set at 15 seconds. This means the routing algorithm will add 15 seconds to the overall time for each tack/ gybe you make. If you see the router suggesting too many tacks/ gybes, you could consider increasing the penalty. Then the router will consider the time taken and possibly not tack/ gybe as often.

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