2026/06/25 by Melissa A. Piper, Ryan D. Torn
Earth and Planetary Sciences · Environmental Science · #Climate variability and models #Meteorological Phenomena and Simulations #Tropical and Extratropical Cyclones Research
paper · doi:10.1175/waf-d-25-0246.1
openalex publication_date 2026/06/25 · openalex created_date 2026/06/26 · openalex updated_date 2026/07/25
Abstract This study analyzes storm-total precipitation forecasts from the National Centers for Environmental Prediction Global Forecast System (GFS) and European Centre for Medium-Range Weather Forecasts (ECMWF) for the contiguous United States (CONUS) landfalling tropical cyclones (TCs) from 2018 to 2024 using an object-based methodology. Forecast errors are quantified in terms of location, precipitation intensity, and size errors for 1- and 5-in. threshold precipitation clusters for 40 cases from 36 landfalling TCs. While there are few signs of forecast error improvement as forecast lead time decreases, the GFS consistently underforecasts precipitation intensities within 1-in. clusters when compared to the ECMWF. In addition, cluster forecast errors are stratified by different TC-related characteristics. Overall, there is no systematic relationship between any cluster forecast error and TC track forecast errors; however, high track error cases have centroid location errors 75–100 km greater than low track error cases for 5-in. threshold clusters in both models. The most robust difference in cluster forecast errors is by landfall intensity, where 5-in. clusters disproportionally occur in hurricanes. Moreover, when compared to hurricanes, tropical depressions and storms exhibit higher 5-in. cluster location errors in the GFS and underforecast all amounts of precipitation in 5-in. clusters in both models. In addition, a GFS forecast for Hurricane Henri (2021) is examined to investigate potential factors leading to a poor location forecast. The GFS forecast appears to more slowly advance a nearby cutoff low, leading to a weaker interaction between the low and Henri and resulting in precipitation being forecast for the wrong location. Significance Statement Tropical cyclone (TC) precipitation forecast verification has traditionally been done using methods that can struggle to provide information on error sources that could be used to improve forecasts. Our study verifies TC precipitation forecasts from 2018 to 2024 using object-based methods that independently assess spatial and intensity errors. We found that the GFS underforecasts the amount of precipitation within 1-in. objects compared to the ECMWF. Additionally, the GFS and ECMWF tend to underforecast all amounts of precipitation for TCs that make landfall as a tropical depression or storm compared to TCs that make landfall as a hurricane. We also looked closer at a forecast from Hurricane Henri to understand what led to a poor precipitation location forecast.