The atmosphere can hold more water, and the oceans hold more heat. Hurricanes thrive on warm water (especially deep warm water, as the hurricane will churn up w

The atmosphere can hold more water, and the oceans hold more heat. Hurricanes thrive on warm water (especially deep warm water, as the hurricane will churn up water from deeper levels, which can weaken it significantly if it's stirring up a lot of cold water). One of the reasons Harvey intensified so quickly is that is passed over a _very_ warm section of the gulf: https://s.w-x.co/wu/ohc_aQG3_2016_237_1200.harvey.int__0.gif https://s.w-x.co/wu/ohc_aQG3_2016_237_1200.harvey.int__0.gif Irma will be passing over similarly warm waters for the next 4-5 days: http://isotherm.rsmas.miami.edu/heat/images/irma/ohc_aQG3_2017_248_1200.irma.int.gif http://isotherm.rsmas.miami.edu/heat/images/irma/ohc_aQG3_20... The northern Leewards and Greater Antilles are in for a _really_ rough time. It's likely a direct hit (or close brush) with either Hispaniola or Cuba will weaken Irma before it turns north into Florida, but that's still really bad news for folks in the northern Caribbean, and it's still going to be a very serious storm when it hits Florida.