In-house radar imagery suggests that Hurricane Isaac made its first landfall on Louisiana soil just after 6:00 PM CT this evening as a Category 1 hurricane.
The eye made it onto land at that time, now on its way to the major landfall on the main Louisiana soil. I will have more detail on this later, as well as verification on my forecasts and projected paths of Isaac.
A horrendous flooding situation is setting up in the central Gulf Coast over the next couple days, as Isaac crawls ashore and stays in place for hours on hours. Here's a new forecast from the WRF. Amounts are in millimeters.
This is a 48 hour total precipitation forecast off the new 12z WRF. It shows 758.6 millimeters of rain that has fallen in southern Louisiana, dangerously close to New Orleans. If one does the calculations, 758.6 millimeters equates to 29.87 inches of rain in 48 hours. That is nothing to mess with, folks.
That's not the only solution printing heavy amounts of precipitation in short periods of time.
Here is the NAM 60 hour total precipitation forecast, also measured in millimeters. The white area shows 1000 millimeters and over. If we put 1000 millimeters to inches, we will find that 39.37 inches or more is predicted by the 12z NAM for the southern Louisiana area- something that cities without major levees would struggle to survive.
The Hydrometeorological Prediction Center (HPC) is being more conservative, with 16 inches predicted to fall over southeast Louisiana. Looking at other models, I find this to be on the low end. Here is my projection.