Friday, August 3, 2012

Ernesto Approaches Barbados

Tropical Storm Ernesto formed in the tropical Atlantic east of the Windward Islands Wednesday afternoon.  Hurricane hunter aircraft found tropical storm force winds even though satellite pictures did not indicate as much organization.  Ernesto was nearing the island of Barbados just after midnight on Thursday morning.  The storm had maximum sustained winds of 50 mph and was moving west at 22 mph.  The latest National Hurricane Center advisory can be found here.

Tropical Storm Ernesto approaching Barbados.  Click on the image for a larger view. Image Credit: NOAA/NHC.
Ernesto will pass through the Windward Islands this morning and head into the Caribbean Sea.  Conditions do not favor significant strengthening over the next few days and the computer models are tightly clustered around a westward path.

Computer model forecasts of the center of the storm.  Image Credit: NCAR.

However, the storm may slowly intensify as it moves through the Caribbean Sea.  Most storms do not reach hurricane strength in the eastern Caribbean if they are not already hurricanes.  Thus, that is not likely until the storm moves into the central or western Caribbean Sea.  Intensity models suggest that the storm may become a hurricane as early as day 3, but more likely day 4 or 5.

Computer model and official forecasts of intensity.  Image Credit: NCAR.
The Bermuda high is centered northeast of Bermuda and is directly north of Ernesto.  The strength of the high is producing a brisk easterly steering current and is why the storm is moving rapidly to the east.

Steering currents over the U.S. and much of the Atlantic Basin.  Image Credit: CIMSS.
What is the storm likely to do?

Ernesto should move quickly through the eastern half of the Caribbean Sea with some strengthening possible.  A weakness in the ridge of high pressure to the north of the storm should occur as it moves into the western Caribbean.  This will allow the system to slow down in its forward speed.  Conditions will also be right for the storm to strengthen further.

Intensity is extremely difficult to forecast beyond three days.  Current forecasts have the storm as a category 1 hurricane.  However, conditions may be right for Ernesto to become a major hurricane (category 3, 4, or 5) by day 5.

At this point the storm would become problematic.  Some of the dynamical models have the system moving into Mexico.  It would certainly threaten parts of the Gulf of Mexico. However, it is difficult to know how far north the storm might go.  A ridge of high pressure aloft is forecast to build into the Gulf coast states toward the end of next week.  This would definitely argue for the system to continue westward into Mexico or southern Texas.  It could become problematic for the oil rigs resulting in evacuations soon.

It is not likely to have any effect on South Carolina.  However, tropical moisture over Cuba and the Bahamas should move into the state by the end of the weekend into early next week.  This will bring scattered afternoon thunderstorms to the Midlands each day from Sunday through Wednesday.

One final word of note: Computer models are forecasting a possible storm forming near the Bahamas and moving northeast.  This is about 10 days out and much can change in that time.  This will be watched as we will be moving into the height of hurricane season about that time.