We received round one of this week’s rain Sunday and yesterday. I received almost 2 inches at my house on the east side of Athens, GA. Tuesday there is a respite before the next deluge begins, although with afternoon heating there is a chance of some showers even today. But the radar shows the next mass of rain heading towards Georgia from southern Mississippi and Alabama. The NWS Southeast River Forecast Center has an online slide set which explains some of their reasoning for current flood potentials at https://www.srh.noaa.gov/media/serfc/alert/DOSM_April_14_2015.pdf. They are a fantastic source of real-time information so be sure to visit their web page whenever flooding conditions are possible.
If you don’t have a rain gauge, how do you know what amount of rain fell? There are a variety of sources online that can give radar estimates or maps of observed precipitation. Here are some of the ones I use. Note that there are many more, so this is not close to an exhaustive list.
Radar-estimated rainfall:
NWS local forecast offices
Each NWS radar site has a way to visualize accumulated precipitation on its site. Here is the one from NWS Peachtree City near Atlanta GA this morning. The advantage to this display is that it is available in real time, but it may be less accurate because it has not been calibrated to what local rain gauges collected and sometimes has problems when hail or freezing conditions are present. The storm total accumulation does not start at a standard time.
NWS national radar estimate
Each morning the NWS produces a national radar estimate of rainfall for the country, which is available at https://water.weather.gov/precip/. The one for today is below. The advantage of this site is that it gives a daily value which can be compared to observations and that it is calibrated to remove some of the issues with ice and heavy rain intensity which can affect the accuracy of the individual radars. It also blends all the local radars into one seamless map. The disadvantage is that it is not available in real time. Their maps show 7 am to 7 am rainfall.
Station-based observations
CoCoRaHS
The CoCoRaHS network is a network of volunteer weather observers who take rainfall observations each morning around the country. They report for 24 hours from roughly 7 am to 7 am. I’ve written about them several times before and am a regional coordinator for Georgia. Here is the map of observations for the Atlanta metro area for this morning.
The Southeast Regional Climate Center has a daily map which shows the midnight-to-midnight rainfall amounts from NWS airport stations at https://www.sercc.com/perspectivesmap.
CRONOS is a website from North Carolina State University with data for many locations across the Southeast. They report values from NWS cooperative volunteers as well as some automated networks around the region, not including the University of Georgia network. Here is this morning’s map from https://www.nc-climate.ncsu.edu/map/?table=daily.
In addition, there are data available from individual states’ automated weather networks, such as the University of Georgia network at https://www.georgiaweather.net and the Georgia Forestry network at https://weather.gfc.state.ga.us. The maps below show the UGA network on the left and the Georgia Forestry map on the right. Note that the maps from the local networks are based on a smaller number of stations and so may miss some local dry areas or heavier rains in their graphing schemes.
