The neXtSIM-F forecast system consists of a stand-alone sea ice model, neXtSIM, forced by the TOPAZ ocean forecast and the ECMWF atmospheric forecast, combined with daily data assimilation. It was tested for the northern winter of 2018 -2019 with different data being assimilated and was found to perform well. Despite drift not being assimilated in our system, we obtain quite good agreement between observations, comparing well to more sophisticated coupled ice-ocean forecast systems. The RMSE in drift speed is around 3 km/day for the first three days, climbing to about 4 km/day for the 5 next day or two; computing the RMSE in the total drift adds about 1 km/day to the error in speed. The drift bias remains close to zero over the whole period from Nov 2018 -Apr 2019. The neXtSIM-F forecast system assimilates OSISAF sea ice concentration products (both SSMI and AMSR2) and SMOS sea ice thickness by modifying the initial conditions daily and adding a compensating heat flux to prevent removed ice growing back too quickly. This greatly improved the agreement of these quantities with observations for the first 3 -4 days of the forecast.(Svalbard) after getting into trouble with sea ice. The crew had to be rescued by the Norwegian Coast Guard icebreaker K.V.Svalbard, who then had to drain 300kL of diesel from the damaged vessel. 2 Thus sea ice forecasting is becoming increasingly important. As well as search and rescue/accident prevention, other applications are optimized ship (icebreaker) routing based on forecasts (Kaleschke et al., 2016) and support of research activities -e.g. Schweiger and Zhang (2015) give an example of scheduling of high-resolution SAR images in order to follow the drift 5 of some ice-mass balance (IMB) buoys by using the PIOMAS/MIZMAS forecast from the University of Washington. The planned year-long drift of the Polarstern from September 2019 (part of the MOSAIC project) will also rely heavily on sea ice and weather forecasts.The sea ice forecast system neXtSIM-F is based on a stand-alone version of the sea ice model neXtSIM (Rampal et al., 2016. The dynamical core of this model is based on the Maxwell-Elasto-Brittle (MEB) rheology as developed for sea ice and 10 originally presented in Dansereau et al. (2016), which showed its capabilities at reproducing the main spatial characteristics of sea ice mechanics and deformation: strain localization and scaling (Marsan et al., 2004;Rampal et al., 2008; Stern and Lindsay, 2009). With the implementation of this rheology in neXtSIM (along with accompanying thermodynamics and general model infrastructure: Rampal et al., 2019), MEB was able to be assessed over longer simulations, and it was found that it could also reproduce the observed temporal deformation scalings, in addition to the spatial ones. In particular, the results show strong 15 multifractality, meaning that higher deformations are more localised in space and more intermittent in time than smaller ones.These properties have strong implications for things like distribution and size of lead op...