OBJECTIVES: 1) DEVELOP AND VALIDATE A TWO-DIMENSIONAL OCEAN CIRCULATION MODEL FORCED BY CYGNSS WIND PRODUCTS FOR STORM SURGE PREDICTION. EVALUATE THREE METHODS FOR INPUTTING CYGNSS WINDS INTO THE MODEL: (I) USE OF A PARAMETERIZED CYCLONE WIND STRUCTURE MODEL CONSTRAINED BY CYGNSS LEVEL 2 WIND PRODUCTS; (II) RAPID DATA ASSIMILATION OF THE LEVEL 2 WIND PRODUCTS VIA USE OF A SLAB-TYPE BOUNDARY LAYER MODEL; AND (III) A SURFACE WIND VECTOR ANALYSIS FIELD DERIVED BY ASSIMILATION OF BOTH CYGNSS LEVEL 2 WIND PRODUCTS AND CONVENTIONAL DATA. CONDUCT PERFORMANCE CHARACTERIZATION OF THE INPUTTING METHODS AND COMPARE CYGNSS-FORCED STORM SURGE RESULTS TO A CONTROL SCENARIO USING TRADITIONAL WIND FORECAST PRODUCTS. 2) DEVELOP A LOCALIZED STORM SURGE PREDICTION SYSTEM THAT DOWNSCALES THE LARGE-SCALE STORM SURGE ASSIMILATION RESULTS TO PRODUCE HIGHRESOLUTION BLOCK-SCALE MAPS OF WATER LEVEL AS A FUNCTION OF PREDICTED STORM SURGE AND PRECIPITATION LEVELS. THE MODEL WILL SUPPORT HIGHRESOLUTION SIMULATIONS OF IMPACTED REGIONS WITH BUILDING-RESOLVED GRIDS TO PREDICT WATER LEVEL AS A FUNCTION OF TIME PRECIPITATION AND STORM SURGE. METHODS/TECHNIQUES: THE ADCIRC OCEAN CIRCULATION MODEL TIGHTLY COUPLED WITH THE SWAN WAVE MODEL WILL BE USED FOR THE STORM SURGE MODELING. SINCE CYGNSS PRODUCTS ARE AVAILABLE AT A MUCH HIGHER TEMPORAL RATE THAN THE TYPICAL 6- TO 12-HOUR FORECAST CYCLE THEIR FULL BENEFIT IS NOT REALIZED IN THE CONTEXT OF THE TRADITIONAL OPERATIONAL FORECAST PARADIGM. A SLAB-TYPE BOUNDARY LAYER MODEL WILL BE DEVELOPED THAT CAN BE INITIALIZED BY THE OPERATIONAL FORECAST BUT THEN UPDATED VIA ASSIMILATION OF CYGNSS WINDS AT A TEMPO CONSISTENT WITH DATA DELIVERY. THE USE OF A SLAB BOUNDARY LAYER MODEL WILL ALLOW FOR RAPID ASSIMILATION OF FIRST-GUESS FULL-FIELD WIND ESTIMATES BASED ON HWRF FORECAST WINDS WITH THE INFORMATION CONTAINED IN THE SPARSELY SAMPLED CYGNSS OBSERVATIONS. A 6-HOURLY SURFACE WIND VECTOR ANALYSIS FIELD DATA PRODUCT DERIVED BY ASSIMILATING BOTH CONVENTIONAL DATA PRODUCTS AND CYGNSS LEVEL 2 WINDS WILL ALSO BE USED TO FURTHER ANALYZE THE TRADEOFF BETWEEN USING CRUDER WIND APPROXIMATIONS THAT ARE UPDATED FREQUENTLY VERSUS A MORE COMPLETE WIND REPRESENTATION THAT IS ONLY AVAILABLE EVERY 6 HOURS. TO ADDRESS THE GAP BETWEEN STORM SURGE FORECASTING SKILL AND PUBLIC UNDERSTANDING OF INDIVIDUALIZED STORM SURGE RISK WE WILL DEVELOP THE FRAMEWORK FOR A LOCALIZED FLOOD FORECASTING TOOL. THE LARGE-SCALE STORM SURGE SIMULATION RESULTS WILL BE DOWNSCALED TO CITY SCALE FOR EASY VISUALIZATION OF TOTAL PREDICTED WATER LEVELS. A TEST CASE FOR HOUSTON TX WILL BE DEVELOPED AND TESTED AGAINST HIGH-WATER MARKS MEASURED DURING HURRICANE HARVEY. THE RESULTING LOCALIZED STORM SURGE INUNDATION MAPS WILL BE USED AS A POINT OF COMPARISON TO ONGOING CYGNSS RESEARCH ON WETLAND AND FLOOD INUNDATION MAPPING. SIGNIFICANCE: STORM SURGE IS A PHENOMENON THAT CAN HAVE DEVASTATING EFFECTS; ITS FORECASTING IS OF INCREASED IMPORTANCE IN LIGHT OF CLIMATE CHANGE LAND SUBSIDENCE AND INCREASED COASTAL POPULATIONS. IMPROVING STORM SURGE PREDICTION USING CYGNSS DATA IS AN ORGANIC APPLICATION OF THE CYGNSS MISSION WHICH ALLOWS FOR MEASUREMENT OF STORM WINDS AT A HIGHER TEMPORAL RESOLUTION THAN TRADITIONAL SATELLITE DATA AFFORDS. THIS WORK WILL COMPLEMENT MANY OF THE CURRENT CYGNSS TEAM MEMBERS' RESEARCH BUILDING ON THE ONGOING WORK AND PROVIDING ADDITIONAL METHODOLOGY FOR COMPARISON AND VALIDATION RELATED TO WAVE MODELING AND OVERLAND INUNDATION. IN ADDITION TO IMPROVING STORM SURGE FORECASTING THIS RESEARCH AIMS TO ADDRESS THE DISCONNECT BETWEEN STORM SURGE AND PUBLIC UNDERSTANDING OF INDIVIDUAL RISK BY DEVELOPING THE FRAMEWORK FOR A LOCALIZED FLOOD MAPPING TOOL WITH EASILY VISUALIZED WATER LEVELS.