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12/23/2020 4:39 am  #1

PW GFS/EC gribs analyzed at North Head weather station - Sydney Harbor

Navigators in Australia, we are so sorry to hear about the cancellation of this year's Sydney-Hobart race.
      In the spirit of still being in "race-mode" we went ahead and ran an analysis of the Predict Wind GFS and EC forecasts against the North Head weather observation station near Sydney. 
       Model Accuracy has a "pre-race" function which allows GRIB files to be compared to weather stations, and we now support the file format of the AuBOM (Australian Bureau of Meteorology) wind observations. This means you can download the weather station log data and use that as the truth against your GRIB file forecasts to see what is the accuracy trend in your area. 
      Take a look below to learn the expect forecast errors are before one ever even heads out to sea!

We compared 2 days of weather instrument data to the PW EC and PW GFS forecasts. We found a significant trend of the TWS forecast being far above what actually occurred, by approximately 7 knots! Check out at the Model Accuracy error graph below of the GRIB forecasts plotted against the observed weather data from North Head weather station.  

Below is the "Results" page of the mathematical and statistical analysis of the forecasts compared to the truth data of the observation station. Both GRIBs were actually similar in their errors of the TWS being 7 knots above and 17-20 degrees right of the observations. Model Accuracy provides exact calibration values to be entered into Expedition Sailing Software for optimal routing of a "corrected" GRIB file.  

Here you can see the TWD error plot. A "perfect" forecast would have "zero" error and would have the colored line respective to the GRIB plotted perfectly horizontal at "0" degrees error value. About a day into the forecast PWEC and PWGFS demonstrate big differences in their TWD forecast as seen by the divergence of the plotted lines and the errors they represent. 



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