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.
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.