So far, Isaac wins the award for the largest mess of a tropical system I can recall. While nearly 1000 miles wide, it has so far remained highly disorganized, thanks in large part to a great deal of dry air that has been caught up in the northern half of the storm. Multiple times today, the National Hurricane Center and Hurricane Hunters flying into the storm have noted "multiple centers" to the storm - individual areas of low pressure within the cloud mass and convection (thunderstorms). If this storm can get organized (which we expect it to tomorrow), it could become a large one to reckon with.
Obviously in forecasting, including for systems like these, meteorologists rely strongly on computer models to provide a clue as to what path a storm will take, how strong it will be, and how fast it will move. Then, intuition kicks in and adjustments are made to the forecast. I'll admit I am NOT a tropical forecaster and have not been specifically trained in hurricane meteorology. However, I can parse a great deal of incoming information and I follow many bright minds in the business for clues on a storm's structure and tendencies. While I don't claim to be able to forecast the track or intensity myself, I DO know a fair amount about what causes these storms to tick, what factors tend to strengthen and weaken them, as well as the potential impacts given a known set of parameters.
First I introduce the current conditions. Below is a recent infrared satellite image as the storm moves generally west, to the south of Puerto Rico and the Dominican Republic. Maximum sustained wind is near 45 mph. The strongest convection (storms) is in the reds and dark grays, mainly southwest of the center. I expect we may see that center re-located somewhat if convection continues in that area as it seems the most likely place for the primary "center" of the storm to appear.
|8:15pm infrared satellite image of Tropical Storm Isaac|
|UPDATED: 10pm CDT official forecast track of Tropical Storm Isaac from NHC|
|Computer model output from several models on Thursday afternoon showing potential tracks for Isaac|
|Computer model output for Thursday evening. Note a general westward "shift" in the potential tracks (as a whole).|
Finally, we look at another suite of forecast tracks, all from the same model (the well-known GFS) but with various possibilities this model considers. Again, the tracks cluster along the north-central Gulf Coast with landfalls ranging from Biloxi to Apalachicola (disregarding a couple of outliers).
|GFS ensemble members forecast tracks for Isaac|
Lastly, let's look at one of the reasons why intensification is likely over the Gulf - water temperatures. Many parts of the Gulf are nearly bathwater temperature, which is like feeding an athlete Wheaties, then injecting steroids. The orange-red colors are temperatures of 86-90+ degrees. Any storm that passes over those waters will get a shot of high-octane fuel.
How about impacts on the Mid-South? It's really too early to tell. However, one thing we are sure of is this - the farther west the track goes in the Gulf, the more likely it is we could feel some impact. A landfall in Louisiana would give us a higher likelihood of rain than landfall in the Florida panhandle. I don't know anyone who wouldn't welcome some rain in the Mid-South after the drought of summer 2012!
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