Why A Warning for Southeast Florida?

The winds have diminished over Southeast Florida, so why did the National Hurricane Center (NHC) issue a Tropical Storm Warning for Noel? The U.S. Air Force Hurricane Hunter plane flying Tropical Storm Noel during the night reported that the extent of tropical storm force winds in the northwest quadrant of the tropical storm has increased. The NHC track forecast has remained fairly consistent and continues to take the center of Noel over Andros Island in the Bahamas and then northeastward across the Abacos. If the NHC has a perfect forecast, the tropical storm force winds associated with Tropical Storm Noel will remain just offshore the Florida coast based on the current forecast. However, a perfect forecast of the track and size of the tropical cyclone (defined by the radius of tropical storm force winds) rarely happens. If the track of Tropical Storm Noel shifts slightly to the west (i.e., closer to Florida), OR if the radius of tropical storm force winds expands in the northwest quadrant, Southeast Florida could experience tropical storm conditions. The probability of this happening is low, but it is not zero.

The Miami Weather Forecast Office sums it up nicely by saying “Conditions at this time are not expected to be any worse than they were over the past couple of days along the coast. The worst conditions will likely be associated with passing rain bands. In this sense, this will be a minimal impact event.”

I think that most people understand the uncertainty related to forecasting the track and intensity of tropical cyclones. Perhaps more education is needed, however, in emphasing the difficulty in forecasting the size of a tropical cyclone. The initial size of a tropical cyclone is difficult enough to determine and depends on the availability of surface reports (land stations, buoys, microwave satellite observations, and aircraft reports of surface winds). The “observing” tools have improved dramatically over recent years. However, operational forecasters have very little guidance on “forecasting” the size of a tropical cyclone.

I have always thought that most folks see color satellite loops, radar animations, and computer model forecasts on television and think that the official forecasts are better than they actually are in reality. The NHC has been very clear in stating that improved guidance on tropical cyclone structure (which includes size, intensity, and radius of maximum winds) must be developed. This is indeed a significant challenge for the meteorological research community.


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