ISAAC UPDATE: The Immediate Concern Is Haiti & Dominican Rep, Then Cuba

Graphic courtesy of AccuWeather

If we strip away the uncertainties in the forecast for now and look at what IS certain.. unfortunately what is certain is that Hispaniola which is a large islands which makes up the nations of Haiti and the Dominican Republic and this island will have to contend with significant rainfall from Isaac as he passes nearby to the south or may skirt the south coast. Whether Isaac remains a storm or becomes a hurricane, the primary concern will be the rains as the huge amount of water sucked up into this system will get squeezed out and enhanced by the 10-12,000 foot mountains of this island, so flooding and mudslides is highly likely.

Topography of Hispaniola (Courtesy of Wikipedia)

The topography map above shows you how mountainous this island is and of course mountains do enhance rainfall thanks to air being forced to rise, cool and condense which produce yet more rain than there already is. The fact that land can enhance rains from a tropical storm or hurricane which already holds the biggest amounts of rainfall is any weather system, is very concerning.

Currently Tropical Storm Isaac remains a 40 mph, weak tropical storm but as we’ve continued to see for days, he waxes and wanes as dry air appears to continue feeding into the circulation. It has also been evident that there have been multiple centres spinning around the circulation and so there is a large energy field which needs to consolidate and wrap into one centre and when that happens, then it’s off to the races potentially for this system increasing towards hurricane status. In other words once this large area of energy consolidates and we get another blow up of deep convection which holds and doesn’t fall apart again, then this system is on it’s way to becoming a hurricane and may have an easier time fighting off any shear or dry air from outwith.

View from Hispaniola (Image courtesy of Wikipedia)

400,000 people living outside since earthquake are most at risk from flooding and mudslides

This storm poses a massive threat to the people of Haiti, especially given that 400,000 remain living outdoors following the massive 7.0 earthquake which struck in 2010, killing an estimated 230,000 people. The likely 6-18 inches of rain with locally higher amounts would be challenging to any region but for a region with tall mountains covered in thick, lush vegitation in which waters can surge down to into highly populated areas where people live in tents is extremely concerning..

Beyond Hispaniola is Cuba

After Isaac brings plenty of trouble to the island of Hispaniola, it’s next major land area will be Cuba, where here too rainfall will be a big concern. However, by the time Cuba faces Isaac, there is much greater likihood that this storm will be stronger, potentially a hurricane and so wind as well as rainfall will be a concern. As of now, the eastern side of this island nation looks to be most at risk from flooding rains and possible damaging winds. This would occur late this weekend.

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