f the current forecasts for Tropical Storm Bonnie pan out, the Louisiana coast may be in for a few rough days of weather starting later this weekend.  Although tropical storm forecasting skill has improved over the last few decades, our ability to predict the size, strength, and point of landfall is still a challenging proposition.  To read more about how NHC's forecast skill has improved, there is a nice discussion on this topic on the NHC web site.

One of the reasons that forecasting these storms is so difficult is because in the tropics, the forces that typically drive movement of large weather systems are very weak, and small errors in the various models used to predict tropical systems can more rapidly lead to larger errors than what we see in the mid-latitudes where the driving forces are stronger.  This is why we see a lot of variation among different model tracks.  So far, the various forecasts for Bonnie are lining up with each other pretty well in a general sense, as shown in the latest official forecast from NHC, along with all of their various model forecast tracks used to generate this forecast, as shown in WDT's iMapHurricane display.  

However, as I was perusing some of our own model output this morning, I noticed that our mesoscale numerical weather prediction system has an interesting twist on Bonnie's path.  While showing a similar path as the official forecast, with landfall along the southern Louisiana coast, it shows a slightly slower motion with landfall on Sunday morning.  From that point, it slows significantly and meanders to the west-southwest, hugging the coast through Monday, with continued on-shore winds and rain.  

 This is one of those cases where I hope our forecast is wrong!  Fortunately, if this forecast turns out to be correct, it does keep Bonnie weak through the entire period, which would minimize damage potential, but would most certainly cause more problems related to flow from the oil spill and related cleanup efforts.