NOAA Atlas 14 and Atlas 15 – A Geeks Guide to Rainfall Intensity Criteria for Safety
Fortunately, the Liar in Chief’s decimation of our advanced civilization as we know it is meeting with substantial feedback from citizens, democratic lawmakers, and most importantly, judges. One of the most critical issues that affects almost all of us was the cancelation of the National Oceanic and Atmospheric Administration’s Atlas 15 – Update to the National Precipitation Frequency Standard. The ludicrous proposition of the illegitimate one has been reversed, and Atlas 15 will be completed, albeit a bit tardy from its previous schedule.
To understand the importance of Atlas 15, let’s first look at Atlas 14, what it is and what it means. Atlas 14 is the title of the latest national rainfall frequency standard used by engineers to protect our culture from flooding among many other things. These atlases look at weather station rainfall data from the beginning of their establishments, often 150 or more years ago, and performs statistical analysis on these data to understand the 100-year storm that the insurance industry uses to protect life and property, among which is the Federal Emergency Management Administration’s (FEMA) Flood Insurance Program that identifies floodplains across the U.S. to keep developers and individuals from building structures in harms way, and insuring those that for whatever reason, are in the regulatory floodplain.
The Atlas 14 program is the latest in a long list of evaluations that looked at rainfall data. For example, Atlas 14 for Texas was the last Atlas 14 to be released, based on data collected through 2017. The previous rainfall intensity evolution was from 1970, so climate change effects are included in Atlas 14 for Texas – up through 2017. For a broad swath of Texas from the coast to 200 miles inland, Atlas 14 shows the old 100-year storm is now the new 25-year storm – a huge jump.
The great challenge with Atlas 14 however, and there are three of them, is that 1) it only looks backwards from 2017, 2) It doesn’t include future warming after 2017, and 3) it is significantly understated because of something called non-stationary data. What this is, is that for normal statistical evaluation to be accurate, the data must be stationary – or not changing. Of course the data are changing; rainfall intensity increases with warming and because of event frequency, that is the reoccurrence of rare flooding of rare flood-producing rainfall events, only the most common rainfall events in our currently warmed climate have now occured. This is because our climate has just recently warmed beyond the natural maximum warmth of our old climate in the last five or ten years, and even more recently, warming has spiked significantly in the last five years. This means that it is likely that only the common rainfall events of the 1-, 2-, and 5-year events have occured. As time passes then, rare and much more extreme events will occur because of current warming. Atlas 14 for Texas doesn’t address any of these important caveats. Atlas 15 on the other hand, does address these issues, albeit with their own caveats, and thankfully, Atlas 15 has been relaunched.
Atlas 15 though will likely be understated as well, though not as much ast Atlas 14’s backwards looking evaluation, because Atlas 15, Part 1, uses high-powered statistics to minimize the understatement from non-stationary data. The understatement cannot be completely eliminated because the future remains unknown, but better advanced statistical technique definitely helps. Atlas 14, Part 2 is the forward-looking solution to Atlas 14, where the best and second best-case warming scenarios of the Intergovernmental Panel on Climate Change (IPCC) have been integrated into Atlas 15’s evaluation to project increasing rainfall intensity out 30 years into the future. This is an excellent start, but the best and second-best IPCC scenarios have already been deemed unachievable, so the challenge continues.
NOAA Atlas 15 – Update to the national Precipitation Frequency Standard
https://water.noaa.gov/about/atlas15
After Brief Delay, NOAA’s Atlas 15 Project Moves Ahead
https://www.floods.org/news-views/policy-matters/after-brief-delay-noaas-atlas-15-project-moves-ahead/#:~:text=NOAA%20has%20confirmed%20that%20they,Atlas%2014%20precipitation%20frequency%20estimates.