RECENT OBSERVATIONAL ANALYSES (NAUD ET AL. 2015; CRESPO AND POSSELT 2016) INDICATE THAT CHANGES IN THE LARGE SCALE ENVIRONMENT ARE ASSOCIATED WITH SYSTEMATIC CHANGES IN CLOUD VERTICAL STRUCTURE IN FRONTAL REGIONS OF EXTRATROPICAL CYCLONES. THESE CHANGES APPEAR TO DEPEND ON THE STAGE OF CYCLONE LIFE CYCLE AS WELL AS THE OCEAN BASIN. THERE IS EVIDENCE TO SUGGEST THAT THE INCIDENCE OF DEEP CONVECTION ALONG FRONTS INCREASES IN A WARMING ENVIRONMENT AND A RECENT CASE STUDY ANALYSIS INDICATES THAT THERE MAY EVEN BE STRATIFORM TO CONVECTIVE TRANSITIONS WITHIN FRONTS DURING THE EVOLUTION OF A SINGLE STORM. CHANGES IN THE CHARACTERISTICS AND COVERAGE OF CONVECTIVE CLOUDINESS HAVE IMPLICATIONS FOR THE EVOLUTION OF PRECIPITATION IN THE MIDDLE LATITUDES IN A WARMING CLIMATE. THERE IS CURRENTLY A LACK OF CONSENSUS AMONG CLIMATE MODEL PREDICTIONS AS TO HOW ETC STRENGTH MAY CHANGE IN THE FUTURE AND RECENT MODEL SENSITIVITY STUDIES INDICATE IT IS LIKELY THAT UNCERTAINTY IN TREATMENT OF FRONTAL SCALE MOIST PROCESSES AND THEIR INTERACTION WITH STORM DYNAMICS IS A KEY CONTRIBUTOR. NASA'S GLOBAL MODELING AND ASSIMILATION OFFICE (GMAO) HAS RECENTLY RELEASED THE SECOND VERSION OF THE MODERN-ERA RETROSPECTIVE ANALYSIS FOR RESEARCH AND APPLICATIONS (MERRA-2). THERE HAVE ALSO BEEN RECENT AND PLANNED SUBSTANTIVE CHANGES TO THE GLOBAL ENVIRONMENTAL OBSERVING SYSTEM (GEOS) MODEL PHYSICS PACKAGES. THE AVAILABILITY OF A ROBUST AND WELL TESTED FRONT IDENTIFICATION ALGORITHM ALONG WITH A NASA-PRODUCED ALGORITHM FOR OBJECTIVELY IDENTIFYING EXTRATROPICAL CYCLONE CENTERS AND STORM TRACKS AND A LARGE ARRAY OF NASA SATELLITE OBSERVATIONS AFFORD THE OPPORTUNITY TO SIMULTANEOUSLY EXAMINE THE INCIDENCE OF STRATIFORM AND CONVECTIVE CLOUDINESS IN FRONTAL ZONES AS WELL AS EVALUATE THE REPRESENTATION OF SYNOPTIC AND MESOSCALE MOIST PROCESSES IN MERRA-2 AND GEOS. THE RESEARCH DESCRIBED IN THIS PROPOSAL WILL APPLY PROVEN TECHNIQUES FOR ANALYSIS OF MOIST PROCESSES IN FRONTAL EXTRATROPICAL CYCLONES TO THE ANALYSIS OF MOIST PROCESSES IN NASA MODELS AND REANALYSES. IT DRAWS UPON A PRE-EXISTING MULTI-YEAR DATABASE OF A-TRAIN TRANSECTS OF MID-LATITUDE FRONTS AND EXTENDS THIS DATABASE TO EXAMINATION OF CONVECTIVE AND STRATIFORM CLOUDINESS IN FRONTAL REGIONS. PARTNERSHIP WITH MODEL DEVELOPERS AT NASA GSFC WILL ALLOW USE OF THE OBSERVATIONS IN MODEL EVALUATION AND IN MODEL PHYSICS SENSITIVITY STUDIES WHICH WILL RESULT IN BETTER CHARACTERIZATION OF MODEL ERROR AND ADVANCES IN MODEL DEVELOPMENT. WE WILL FOCUS SPECIFICALLY ON REPRESENTATION OF MOIST PROCESSES IN THE NEW MERRA-2 REANALYSIS AND ON THE REALISM OF SIMULATED CONVECTIVE AND LARGE SCALE PRECIPITATION FROM THE GEOS MODEL. A KEY QUESTION WE WILL ADDRESS IN ANALYZING THE GEOS SIMULATIONS IS THE EFFECT OF DECREASING GRID CELL SIZE (INCREASING RESOLUTION) ON THE REALISM OF FRONTAL CLOUDS AND PRECIPITATION.