NHC has increased the chance of development of a tropical wave in the Atlantic to 30% in the next 7-days. However, model guidance is split on whether it will become a tropical storm with the European model (ECMWF) ensembles much more insistent than NOAA GFS/GEFS.

When will we know which model output is correct? Trends, my friend. If a particular model increases the ensemble members showing development — or conversely poofs, then we’ll have better confidence. Also, we can look at the Artificial Intelligence (AI) trained models from ECMWF (AIFS) and GraphCast, which are dependent upon the ECMWF IFS analysis. NOAA now runs its own version of GraphCast dependent upon its own GDAS analysis. I will collect forecasts and post some results ASAP.