Testing the idea of eye-following inner radius, we tried a constant inner core of 30 to 60km. The variability of radius of maximum winds was generally within this range, but has both storm-length trends and diurnal variation within that range. For our 13 runs of Typhoon Mangkhut, the standard deviation of the eye-radius ranged from 8 to 24 km.

Figure S2: predicted maximum wind speed compared to COAMPS using model developed from constant radius near-eye region, showing the high wind speed bias in the model predictions. The black plusses show the actual observed COAMPS max wind speed from Mangkhut, the red line shows the three hour smoothing used for the LSTM validation, and the blue line shows the LSTM prediction of maximum winds.

And while the trends captured in the mean behavior of the fixed radius and eye-following radius were largely similar, the first order deviations from the mean were meaningfully different. In figures S3 and S4, the surface heat flux is shown. The data from COAMPS was separated in the ring into the mean value, first, and second order sine series residuals, where each order is based on a curve fitting of a sine function around the circle with an output of angle of offset and an amplitude. As the LSTM model we developed used both the first order asymmetry heatflux and the angle of first order for vorticity at 500 and 850mb, which both depend on the inner core region dynamics, the model output went from a prediction with a 2.75 kts mean absolute error (MAE) with eye-following inner region to 8.2 kts MAE with the constant inner region.