THIS PROPOSAL IS AIMED AT SECTION 2.2 OF THE NASA ROSES PROGRAM ELEMENT A.23 (WEATHER AND ATMOSPHERIC DYNAMICS) WHICH IS FOCUSED ON UTILIZING THE SOON TO BE LAUNCHED CYCLONE GLOBAL NAVIGATION SATELLITE SYSTEM (CYGNSS) SATELLITE MISSION FOR THE STUDY OF THE MADDEN-JULIAN OSCILLATION (MJO) AND TROPICAL CYCLONES. AFTER ITS LAUNCH SCHEDULED FOR LATE 2016 CYGNSS WILL BE UNIQUE IN ITS ABILITY TO PROVIDE SURFACE WIND SPEED DATA IN CONVECTIVE WEATHER PHENOMENA IN THE TROPICS WITH MULTIPLE REVISIT TIMES PER DAY. THE PROPOSED PROJECT HAS TWO MAIN OBJECTIVES. THE FIRST OBJECTIVE IS TO PROVIDE A NEW SUPERIOR-QUALITY GLOBAL 4X DAILY GRIDDED OCEAN SURFACE WIND PRODUCT USING CYGNSS DATA FOR USE BY NASA PIS AND THE BROADER COMMUNITY. THE SECOND OBJECTIVE IS TO ADDRESS SEVERAL QUESTIONS FROM A PHENOMENOLOGICAL PERSPECTIVE. THE FIRST PHENOMENA TO BE EXPLORED IN DEPTH ARE AFRICAN EASTERLY WAVES AND OTHER PRE-DEPRESSION DISTURBANCES IN THE TROPICS. THE ADDED VALUE BROUGHT BY THE CYGNSS DATA TO SURFACE WIND ANALYSES WILL BE EVALUATED QUANTITATIVELY AND DIAGNOSED QUALITATIVELY INCLUDING THEIR IMPACT ON THE REPRESENTATION OF SURFACE CIRCULATIONS AT THE TIME OF TROPICAL CYCLOGENESIS. THE SECOND PHENOMENA OF FOCUS ARE WESTERLY WIND BURSTS IN THE MADDEN-JULIAN OSCILLATION (MJO) AND THE ROLE OF CYGNSS IN MODIFYING THE SPATIO-TEMPORAL CHARACTERISTICS OF MJO WINDS WILL BE EXAMINED. FOR THE THIRD QUESTION THE QUANTITATIVE STATISTICS WILL BE USED TO PROVIDE GUIDANCE ON THE TROPICAL FEATURES IN WHICH CYGNSS IS FOUND TO HAVE THE MOST SUBSTANTIAL IMPACT IN THE ANALYSES. THREE SURFACE WIND VECTOR ANALYSIS FIELDS WILL BE CREATED USING THE VARIATIONAL ANALYSIS METHOD (VAM) TO ASSIMILATE THE CYGNSS SURFACE WIND SPEED DATA. THE THREE BACKGROUND FIELDS WITH WHICH CYGNSS DATA WILL BE BLENDED WILL BE THE NOAA/NCEP OPERATIONAL GLOBAL FORECAST SYSTEM (GFS) ANALYSIS NASA S MERRA-2 REANALYSIS AND THE CROSS-CALIBRATED MULTI-PLATFORM REANALYSIS (CCMP). THE ANALYSIS FIELDS WILL BE CREATED DAILY FOR JUNE-NOVEMBER EACH YEAR. THE SURFACE WIND ANALYSES ARE EXPECTED TO PROVIDE SEVERAL BENEFITS TO THE FIELD. FIRST THE IMPROVED ANALYSES OF TROPICAL WAVES MJO WINDS AND OTHER OSCILLATIONS WILL SERVE TO ADVANCE THE SCIENTIFIC COMMUNITY S UNDERSTANDING OF THEIR CHARACTERISTICS AND BEHAVIOR. ADDITIONALLY THE SURFACE WIND ANALYSES CAN BE USED FOR ASSIMILATION IN FULL-PHYSICS THREE-DIMENSIONAL MODELS AND ALSO TO IMPROVE COUPLED MODELING OF OCEAN-ATMOSPHERE INTERACTIONS. A KEY METRIC OF SUCCESS WILL BE THE QUALITATIVE AND QUANTITATIVE DEMONSTRATION OF THE PHENOMENA FOR WHICH CYGNSS DATA ARE MOST ESSENTIAL FOR IMPROVING ANALYSES. GUIDANCE WILL ALSO BE PROVIDED ON WHERE DATA GAPS REMAIN AND WHERE FUTURE SURFACE WIND DATA MAY BE ESPECIALLY USEFUL IN THE TROPICAL AND SUBTROPICAL LATITUDES.