Saturday, August 25, 2012

Isaac Crosses Haiti, Cuba & Florida Straits Next

Tropical Storm Isaac continues to churn through the Caribbean Islands, crossing Haiti last night and only weakening modestly as it crossed one of the less mountainous parts of Hispaniola. It will cross the tip of eastern Cuba today and tonight, likely getting into the Florida Strait at some point on Sunday after skirting along just north of Cuba in the Atlantic later tonight. It will weaken some in all likelihood over the next 24 hours as it deals with land but once over the open ocean should intensify again and likely will become a hurricane on Sunday night or Monday.  One drawback is some shear from a disturbance to Isaac's northwest over South Florida, which may spawn some unfavorable upper winds later today and slow any development.

The model spread, except for the Canadian model (pink track) is pretty consistent on a landfall point in the Florida Panhandle -- looking like Fort Walton Beach or someplace near there on Tuesday afternoon or evening.  There's about a nine hour spread between the GFS and Euro on landfall timing but the landfall point is pretty consistent between the two.  Isaac has a shot at becoming a pretty strong hurricane in the Eastern Gulf for a time, perhaps even a Category 3 as atmospheric conditions in the East Gulf are solid from a tropical development standpoint.   The storm's core will avoid the Florida peninsula (and specifically Tampa) although gusty winds and heavy rain will be likely across the state as the storm tracks through.   The panhandle will not be spared from this storm in all likelihood.

The big question is what ends up happening after landfall.  The storm will slow down markedly as it hits the coast and then gradually works inland.  The question is whether it stalls over the Southeast (Georgia, Alabama) as the GFS (red track) and UK models suggest, or if it bends back slowly into Mississippi as the Euro model suggests (blue track).  In either case, the storm will dump a ton of rain across the Deep South and flooding is likely down there.  The GFS scenario spins the storm out over the Southeast and keeps the remnant moisture away from us.  The Euro scenario suggests that the remnant moisture eventually gets sucked up into a frontal boundary that crosses our region over Labor Day weekend, bringing us some enhanced rainfall as it crosses us by.  The "what happens, if anything, for Philly" gameplan is still in flux and can very much change...much of it dependent on what Isaac does post landfall and how it meanders around across the Southeast.