I was poking around the Atlas 14 website and found a quarterly report from July 2017. Atlas 14 is the national effort to update rainfall statistics based on the very best rain gage data with good geographic coverage and the longest history (time period) available.  The work for most of the country has been completed, except for Texas and some states in the Pacific Northwest. Two key items from the report are discussed in this short post.

First, the results for Texas will be published in May 2018. As I posted earlier, this will likely revise upwards our estimate of the 1% annual chance, 24-hour event, from around 12 or 13 inches to perhaps 14 to 16 inches (depending upon what area of Harris County you are interested in).  This will require bayou modeling updates and updates to the regulatory floodplains – they will get wider and deeper.

Second, the progress report includes a section entitled: “Analysis of Impacts of Non-Stationary Climate on Precipitation Frequency Estimates.” This can be roughly translated to mean: “How might climate change alter rainfall statistics in the future?”

The Atlas 14 effort is a backward-looking effort. The study team is applying standard statistical tools to the available rainfall records to predict the likelihood of rain events of various depths in the future. This assumes that history is good predictor of the future.

The “non-stationary climate” analysis is starting to look at how a changing climate might alter things. The quarterly progress report indicates that the Federal Highway Administration tasked the study team to conduct a pilot project to look at how a changing climate might alter the future. The report indicates that “preliminary findings were inconclusive and the pilot project ended with more questions than answers.”

The project team promises to work with academia (Penn State and University of Illinois, Urbana-Champaign) and to report on further work in the next quarterly report.

So stay tuned.