Forecasters at the National Hurricane Center employ a variety of quantitative models to aid in the analysis and forecasting of tropical cyclones. A subset of these models, referred to as the NHC guidance suite, is a collection of simpler models typically based on climatology and statistical methods. The current NHC guidance suite is based on outdated FORTRAN 77 code. CIRA researchers are assisting NHC personnel in updating the guidance suite code. The process will take in stages and will include not only newer Fortran standards, but also a review of the mechanics of the code itself, for example, checking for consistency of numerical constants among the programs, and making sure the code correctly handles International Date Line and Prime Meridian crossings. The first update was delivered to NHC this week. (POC: M. DeMaria, Mark.Demaria@colostate.edu, R. DeMaria, Robert.Demaria@colostate.edu, J. Dostalek, Jack.Dostalek@colostate.edu, K. Musgrave, Kate.Musgrave@colostate.edu , Funding: Hurricane Supplemental)