JACKSONVILLE, Fla. – The yellow polygon reaching out to Florida is significant, but don’t confuse it for the hurricane “cone of concern.”
There is a big difference between the National Hurricane Center’s (NHC) hurricane track cone and the Graphical Tropical Outlook Graphic.
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Most people look at the NHC track forecast cone, which depicts the forecast track of the center of a tropical cyclone at specific locations out to five days.
The disturbance we are tracking is just a clump of clouds and has not organized into a swirling circulation of tropical activity.
The probability of a disturbance organizing into something greater is routinely discussed in the NHC’s Tropical Weather Outlook Graphic.
Polygons highlight potential areas where tropical cyclone formation may develop during the 48- and 120-hour time periods.
Over the next couple of days, a tropical wave is being closely watched in the eastern Caribbean has a low 20% chance of developing into a tropical depression or storm.
Those are low odds and nothing to stress over.
For instance, of the 63 disturbances tracked last year by the NHC, 67% of the time nothing materialized after issuing a low 20% likelihood of development out to 48 hours.
But be on guard when the odds increase above 60%, since most of the time tropical systems occurred. In fact, a tropical system developed every time the 48 Hour probability reached 80% or higher.
On average, about 60 tropical waves travel across the Atlantic Ocean from Africa each year, with roughly one in five of these becoming a developed system.
According to Dr. Chris Landsea, only about 60% of the tropical storms and Category 1 and Category 2 hurricanes originate from easterly waves, but nearly 85% of the major hurricanes have their origins as easterly waves.
Verification is based on NHC best-track data, with the time of genesis defined to be the first tropical cyclone point appearing in the best track.