Slow Decay of Landfalling Hurricanes in a Warming World

Abstract:

It is well known that where a hurricane strikes land, the destruction of life and property is confined to a narrow coastal area. This is because hurricanes are fueled by the moisture from the ocean, with the implication that their intensity decays rapidly after striking land. In contrast to the effect of a warming climate on hurricane intensification, many aspects of which are fairly well understood, little is known of the corresponding effect on hurricane decay. We analyze intensity data for North Atlantic landfalling hurricanes to show that the timescale of hurricane decay has increased in direct proportion to a contemporaneous rise in the sea-surface temperature over the past 50 years. Thus, in the late 1960s, a typical hurricane lost ∼75% of its intensity in the first day past landfall; now, the corresponding figure is only ∼50%. We also show, using computational simulations, that the increase in the timescale of decay with rise in the sea-surface temperature is caused by a concomitant rise in the stock of moisture which a hurricane carries as it hits land and which constitutes a source of heat that is not considered in theoretical models of decay. Additionally, we show that climate-modulated changes in the hurricane tracks also contribute to the slow decay. Our findings suggest that as the world continues to warm, the destructive power of hurricanes will be projected farther inland than ever before.