Skip to main content
U.S. flag

An official website of the United States government

Investigating Tropical and Post–Tropical Cyclone Extreme Precipitation Based on Storm Intensity and Phase

Presentation Date
Monday, January 24, 2022 at 10:45am
George R. Brown Convention Center - Remote



Tropical cyclones (TCs) and their associated precipitation can have devastating impacts on the areas affected, with outcomes ranging from mudslides to inland flash flooding. Most previous studies have used a fixed radius around the TC trajectory to isolate storm-related precipitation while only one instead used a changing radius based on the 8 m/s radial wind profile, which is a field that can rapidly deteriorate before the dissipation of precipitation risks depending on the storm intensity and completion of extratropical transition (ET). The present study uses a dynamical radius derived from the 500 hPa geopotential height in and around the TC to define TC- and post-tropical cyclone (PTC)- related extreme precipitation, allowing for the analysis of precipitation with tropical origins long after the official demise of the original TC. This novel approach permits the tracking of extreme precipitation related to TCs throughout and following the completion of ET and translation into the downstream regions of global TC basins. Once basic climatologies are constructed, the analysis of TC and PTC precipitation can be broken down by specific storm intensities as well as by the tropical and nontropical phases of a storm's life. Using this algorithm's capability to narrow down the climatologies, this study attributes the amount of total global precipitation and extreme precipitation to the storms that fall into each respective classification category. PTC-related extreme precipitation accounts for as much as 40% of the extreme precipitation in the northwest portion of the West North Pacific basin and 3.13% of extreme precipitation globally. On average as many as 7 events of this nature occur each year in areas near Japan, while the Eastern United States typically only experiences 1 or 2 PTC precipitation events each year. When classifying storms based on the intensity at each point in the storm's life cycle, we observe that major hurricanes (storms with wind speeds greater than 49 m/s) contribute on average 2.6% of the global TC- and PTC-related precipitation, while the far less intense but more common tropical storm strength cyclones (having winds of less than 17 m/s) contribute 85.7% of this observed TC and PTC precipitation. This analysis framework is being further extended to assess climate model projections of TC- and PTC precipitation as represented in several high-resolution climate models that are part of the CMIP6 HighResMIP ensemble.

Funding Program Area(s)