Weather Nerd

Gustav hits Haiti, weakens slightly -- for now

The 5:00 PM advisory on Hurricane Gustav is out. Here’s the discussion. There is little change to the forecast reasoning. The storm has made landfall in Haiti, and is now traversing that country’s southwestern peninsula. Due to land interaction, winds have decreased to 75 mph and pressure has risen to 992 mb.

Gustav will probably weaken to a tropical storm this evening. As Alan Sullivan says, Haiti’s hilly terrain “will definitely disturb the structure of the system: Gustav’s core is not very big, which makes it more susceptible to disruption.” Indeed, the disruption may be greater than expected, since, according to Dr. Jeff Masters, Gustav will take a “longer than expected track … over Haiti.”

But don’t be fooled. By midnight, Gustav will have re-emerged over open water — some of the warmest water in the ocean, in fact — and significant re-intensification is likely tomorrow, Thursday and Friday, with the degree of intensification depending on Gustav’s exact track.

Dr. Masters thinks “it should take 24-36 hours for Gustav to recover from its encounter with the high mountains of Hispaniola and become a hurricane again–or longer, if the storm passes close to or over Cuba.” But he adds, “intensification is likely whenever the storm is over water, at least 50 miles from land,” and “with high oceanic heat content also present in the waters off western Cuba, the potential for rapid intensification exists should the center stay more than 50 miles from the Cuban coast.”

In the mean time, what can Haiti expect from Gustav? Dr. Masters writes:

Gustav is a small storm, and wind damage from Gustav will be confined to a 50-mile diameter area along Haiti’s southwest peninsula. Gustav’s hurricane-force winds will miss Haiti’s capital, Port-au-Prince. As always, heavy rain will be Haiti’s main concern, due to the heavy deforestation on the steep mountainsides that allow deadly flash floods to pour unchecked into Haiti’s populated areas. Flooding from Tropical Storm Fay killed 20 Haitians last week, and we can expect serious flooding along Haiti’s southern reaches from Gustav. Gustav is moving a modest 9 mph, but is expected to slow down later today and Wednesday, extending the period of time Haiti is exposed to the storm’s flooding rains.