Over the past 30 years, the location where tropical cyclones reach maximum intensity has been shifting toward the poles in both the northern and southern hemispheres at a rate of about 35 miles, or one-half a degree of latitude, per decade according to a new study, “The Poleward Migration of the Location of Tropical Cyclone Maximum Intensity,” published in Nature.
As tropical cyclones move into higher latitudes, some regions closer to the equator may experience reduced risk, while coastal populations and infrastructure poleward of the tropics may experience increased risk. With their devastating winds and flooding, tropical cyclones can especially endanger coastal cities not adequately prepared for them. Additionally, regions in the tropics that depend on cyclones’ rainfall to help replenish water resources may be at risk for lower water availability as the storms migrate away from them.Typhoon Francisco and Super Typhoon Lekima on October 23, 2013 as they tracked northwestward toward China and Japan. Credit: Tim Olander and Rick Kohrs, Space Science and Engineering Center Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison. Based on Japan Meteorological Agency data.
The amount of poleward migration varies by region. The greatest migration is found in the northern and southern Pacific and South Indian Oceans, but there is no evidence that the peak intensity of Atlantic hurricanes has migrated poleward in the past 30 years.
By using the locations where tropical cyclones reach their maximum intensity, the scientists have high confidence in their results.
“Historical intensity estimates can be very inconsistent over time, but the location where a tropical cyclone reaches its maximum intensity is a more reliable value and less likely to be influenced by data discrepancies or uncertainties,” said Jim Kossin, the paper’s lead author, who is a scientist with NOAA’s National Climatic Data Center currently stationed at the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin–Madison.
The one wrench in the data though is that total tropical activity has actually declined steadily since 1980 and is now in one of the quietest periods in the last century. This may have adverse effects on the results of this study because there are fewer strong hurricanes in the “more typical” zones in the oceans, which could skew data further north. More time and research will need to be done to know for sure, along with what’s causing the potential shift.?