RaInDROP Tool

April 7, 2025
Release of RaInDROP Version two (V2). This version corrects for precipitation depth errors noted for the Southern Mountains in RaInDROP V1. Specifically, the NOAA Atlas 14 precipitation depth dataset we originally used merged different Atlas 14 volumes.

Unbeknownst to us, this merging (with a smoothing technique applied) created problems at the boundary between NC and Georgia. Additionally, RaInDROP V2 uses the Annual Maximum Series (AMS) and is now more consistent with the scale-factor methodology used to derive future rainfall depths. Note that RaInDROP V1 used the Partial Duration Series (PDS) for scaling, and hence, small differences may be noted for other locations within NC, but these differences are insignificant relative to future uncertainties. Precipitation depth projections were also created for all HUC-10 basins that intersect NC to assist with watershed-related issues identified by stakeholders.

To find out more details about RaInDROP V2, such as the error correction for the Southern Mountains, please read the supplemental document.

To view all tool updates, view our updates page.

Extreme precipitation events can sometimes occur with greater intensity, frequency, or duration, leading to conditions that favor more widespread or severe flooding. Warmer temperatures can also increase evaporation rates, resulting in more atmospheric moisture and the potential for heavier precipitation.

The current practice within the United States is to use NOAA Atlas 14 Intensity-Duration-Frequency (IDF) precipitation values for set durations (e.g., 24-hour) and return periods (e.g., 50-year storm). Since the release of the next version, Atlas 15, is still several years away, the State Climate Office of North Carolina developed a dataset that illustrates how precipitation patterns represented in Atlas 14 may evolve over time.  

This effort adjusted NOAA Atlas 14 values across North Carolina using scale factors derived from a statistical downscaled dataset. The analysis examined plausible changes for two periods (mid-century and end-of-century) and two modeled future conditions (moderate and high scenarios). IDF curves were then created to help quantify changes in regional precipitation extremes.  The adjustment factors were derived from a statistical downscaled dataset – Localized Constructed Analogs (LOCA) which has approximately a 6-km horizontal resolution. The LOCA datasets were previously used in the Fourth and Fifth National Climate Assessments.

These adjustment factors were applied to NOAA Atlas 14 data at individual grid points across North Carolina to develop a tool that provides point-based frequency estimates of rainfall depth and rainfall intensity. This Rainfall, Intensity, Duration and Return for Observations and Projections (RaInDROP) Tool lets users conveniently explore updated precipitation frequency information. 

Additional features will be added to this tool in the near future, such as sub-hourly data.