Question: Why reported wind speed of hurricane is much higher than value forecasted by Windy?
Answer: Windy displays ECMWF or GFS global forecast model. Neither of them is capable to predict exact peak values.
- Modeling: Numerical model computes grid that has finite resolution in both space and time (~10km in space horizontally, ~100-1000m vertically, ~1-6h in time). Peak values are smoothed, because of coarse grid resolution.
- Analysis of input data: Calculations are based on measurements. They come from stations, radars, satellites and other sensors. These sensors are not always reliable, so extremal measurements can be considered as errors during data assimilation and thrown away to avoid damaging the computation.
- Numerical models are not good at prediction of local extreme values and phenomena. Examples: tornadoes, convective storms, hails, single convective clouds, single orographic clouds, extreme wind speed in storms or hurricanes.
- Numerical models are good at prediction of averege and "smooth" values. Examples: average wind in last 3 hours, temperature, humidity, pressure field.