The Tough Times of Forecasting Isaac

          Tropical storm Isaac was the first hurricane to make direct U.S. landfall this year. It was a storm of unusual timing and confusion, which led to the extreme amount of media coverage over the past week.

TS Isaac managed to delay the RNC

          The timing of this system could not have been worse. Earlier this week Isaac managed to postpone the Republican National Convention in Tampa, Florida, while school systems in Southern Florida cancelled their Monday classes. Once all of this mitigation was in place Isaac ironically managed to spare much of the Eastern coastline of Florida minus the Keys.

           Much chaos surrounded the actual projected path of Isaac as it made its way into the Caribbean. Weather computer models had anything from the storm brushing up against the Atlantic coast to making direct landfall in Louisiana. The path of Isaac was directly correlated with the speed and strength of a high pressure ridge, which was predicted to make its way across the United States. Three different weather models (complex equations that predict future conditions of the atmosphere) pushed out different results. The Canadian Model predicted that this ridge of high pressure would drive Isaac on a more eastern path into the Atlantic Ocean. The European Weather Modeling system believed that the ridge would dissipate causing Isaac to break into the middle of the Gulf of Mexico. The United States weather model, known as the GFS, predicted a path that would directly impact Florida. These models helped generate the cone of uncertainty of the system.

Wx Models had Isaac making landfall anywhere from New York to Louisiana

         The Weather-computing model that ended up winning out was the European Model, which has supposedly been the most accurate at tropical forecasting in the recent years. The next difficult task, which meteorologists faced, was predicting the intensity of the storm. The storm initially was to be at hurricane strength shortly after passing through the Florida Keys. The initial hypothesis suggested that Isaac would be a strong category 2 hurricane at landfall. In order for it to be classified a category 2 storm the winds must be between 96-110 miles per hour, which brings with it storm surge of 6 -8 feet. Over time, it became evident that the storm was battling dry air entrainment (dry air entering a moist system) and wind shear (Different direction or speeds of winds at different levels of the atmosphere, which can cause weak cloud structure). Both of these factors often inhibit intensification of a tropical system.

           Wind speed slowly intensified while the storm rapidly dropped in pressure. Pressure of the storm is loosely correlated with a tropical system’s wind speed. As Tropical Storm Isaac slowly inched his way to landfall the pressure dropped to a typical category 2 hurricane, which puzzled many meteorologists. Isaac broke a North Atlantic record for having the lowest pressure level ever recorded in a Tropical Storm. There was much disagreement among meteorologists as to when it should have been dubbed a hurricane. The National Hurricane Center felt that the classification system should be a cut and dry yes or no decision. Others felt that there were winds somewhere in the system at hurricane strength and that hurricane status should have been issued early Tuesday morning to urge lingering residents to evacuate low-lying locations of Southeastern Louisiana. 

          Early Tuesday afternoon Tropical Storm Isaac upgraded his status and a hurricane was born. The system’s strongest winds topped out at 80 miles per hour as it slammed the Louisiana, Mississippi, and Alabama coastlines. The hurricane managed to generate enough surge to top 8 foot levees, which left many residents on their rooftops awaiting rescue. New Orleans had rainfall totals that topped 20 inches. Others storm totals can be seen here: http://www.nola.com/hurricane/index.ssf/2012/08/isaacs_rainfall_totals_through.html

ABC News

          The storm has now transitioned into a Tropical Depression as it moves into the Midwest just in time for Labor Day weekend. Locations of Indiana, Ohio, and Illinois should expect a rainfall total ranging from 1-5 inches over the next few days. CNN Money has already released an article stating that the destruction caused by Isaac could hit 2 Billion dollars in damage. See here: http://money.cnn.com/2012/08/31/news/economy/isaac-damages/

          Even though Hurricane Isaac is no more, individuals should be wary for the continuation of activity in the Atlantic Ocean. The months of September and October are generally the most active of Hurricane season. The ocean waters are warmest in the Atlantic and Gulf of Mexico during this time year.