Isaac Update

Tropical Storm Isaac is taking aim at the Gulf Coast Tuesday with a likely landfall in Southeast Louisiana by late Tuesday evening. Isaac will make its closest approach to New Orleans Wednesday morning.  Although this is basically a worst case scenario forecast track for New Orleans, the low intensity of the storm will spare the region from a major disaster, such as what occurred almost exactly 7 years ago with Katrina.  As of 10 PM CDT Monday, maximum winds have remain at 70 MPH, slightly short of the 74 MPH threshold for a hurricane. Isaac will likely become a hurricane later on Tuesday, but will likely not have time to strengthen beyond category 1 before landfall. The absolute worst case scenario here would be Isaac making landfall as a low end category 2 hurricane, but that appears increasingly unlikely.  Although Isaac is over warm waters, it struggles with dry mid level air becoming entrained into the center. This dry air has been keeping Isaac weaker than forecast. Although Isaac is slowly mixing out the drier air surrounding it, there is little time for the system to pick up a lot more intensity before landfall. The latest forecast track shows Isaac most likely moving across the Louisiana Coast around 8 PM Tuesday. Isaac will weaken quickly after landfall,. but the system will continue to spread heavy rain inland, reaching Arkansas by Thursday afternoon.

Although computer models are in much better agreement now about landfall in Southeast Louisiana, there remains considerable spread after landfall.

The models are almost evenly spread across the State, making this a tricky forecast. If Isaac moves just West of Central Arkansas, that would bring heavy, potentially flooding rains to Central Arkansas by late Thursday into Friday. Should the center go across Eastern Arkansas, that would mean much less rain for Central Arkansas. It is important to remember the heaviest rainfall is typically found along and to the East of the track. This is the forecast rainfall over the next 5 days from the Hydro-meteorological Prediction Center based on the current National Hurricane Center forecast track

Notice the heaviest rains along and to the east of the forecast center, with a fairly tight gradient on the west side. Under this scenario, very heavy rain would fall across the Eastern half of Arkansas with widespread 3 to 6 inches likely and locally heavier amounts. Rainfall amounts would rapidly diminish heading toward the Oklahoma border. Notice the sharp rainfall gradient West of the track. This is why rainfall amounts will be highly dependent upon the exact track of the center, so this forecast can easily change over the next couple of days. The most likely timing of the heaviest rain for Central Arkansas is late Thursday into Friday morning. Tropical systems can also produce severe weather as they move inland, especially on the Eastern side of the track.