Tropical Storm Colin has come and gone, and you might wonder how much rain we got from the storm as it passed.  Of course, the amount you got depends critically on where you are.  Here in Athens where we were just on the edge of the storm I got a paltry 0.22 inches, and not all of that was from Colin.  But other areas got a lot more, in some places causing minor flooding.

You can get rainfall amounts from individual observers using NWS cooperative observer reports or CoCoRaHS observations, but for the most complete coverage you usually need to use something like radar-estimated rainfall to fill in the gaps between ground observers.  Fortunately there are a number of sources of this.

The North Carolina State Climate office has a nice interactive map which shows radar-estimated rainfall calibrated to rain gauges at https://climate.ncsu.edu/mpe_departure/. You can see that map for TS Colin below.  It shows areas with more than 6.5 inches as a streak of purple crossing the Florida peninsula near Gainesville FL.  There are other areas of heavy rain east of Tampa and near Tallahassee.  The Georgia State Climate office used similar information to develop their own map just for Georgia, also shown below.  Differences are due to the way the contour maps are generated.

colin ncsu mpega sco collin rainfall map 6-6-2016

Another source of data is the NWS Advanced Hydrologic Prediction Services site https://water.weather.gov/precip/, shown below. There are some differences between this map and the previous ones.  Some of them have to do with the color scale that was chosen to represent rainfall contours on the map and the time period over which the rainfall was accumulated.  But there are other differences too, such as the thin streak of white in the map below to the west of Gainesville which represents rain of more than 10 inches.  You can’t really see it in the first map, so most likely it was changed based on ground data to be more representative of actual measured rain.  Climatologists hope that all of these different methods of estimating rainfall from radar give comparable results, but it can be a tough task, which is why we always want to compare it to actual rain gauge measurements to get the “ground truth”.

colin ahps radar map