Gauge Adjusted Rainfall information from Baltimore County for Real-time Forecast of Hurricane Rainfall

Baltimore County is located 70-90 km northeast of the Sterling Virginia NEXRAD radar and is an ideal candidate for the use of calibrated radar rainfall data. The county maintains a rain gauge network of 59 gauges with a density of approximately 1 gauge per 25 km2. The RJN Group maintains the network for the County and performs quality control analysis of the rain data. In addition RJN delivers gauge adjusted radar rainfall data to the County through the use of CALAMAR software.The gauges record rainfall in 5-minute intervals and the resulting data are used by CALAMAR software to produce 5-minute rain accumulation data in 1 km2 grids. The rainfall data in grids are converted to sewer-shed rainfall by joining sewer shed boundaries with the grid patterns. The result is a set of sewer-shed-specific files of 5-minute rainfall data. The sewershed rain files may be used by Sliicer.com software to calculate Rainfall Dependent Infiltration & Inflow (RDII) and also by hydraulic modellers to calibrate the runoff characteristics of each sewershedHurrican Irene in 2011 provided an opportunity to evaluate the performace of the gauge adjusted radar during heavy rainfall and also to evaluate how well the CALAMAR system was able to predict rainfall amounts in advance (Nowcast).