Hurricane Isaac Track Chart, Advisory #11
 

Current Location: 14.6N, 42.6W
Geographic Reference: 1225 miles east of Martinique
Movement: West at 16 mph
Max Winds: 75 mph gusting to 90 mph
Current Hurricane Severity Index: 8 out of a possible 50 points (3 size, 5 intensity)
Max Predicted Hurricane Severity Index: 10 out of a possible 50 points (3 size, 7 intensity)
Current Radius of Tropical Storm-Force Winds: 60 miles
Max Predicted Radius of Tropical Storm-Force Winds: 90 miles
Organizational Trend: Slowly Strengthening
Forecast Confidence: Average

Key Points
1. Isaac is predicted to strike the central Lesser Antilles as a hurricane or strong tropical storm Thursday morning.
2. Weakening is expected in the Caribbean due to strong wind shear.

Our Forecast
Isaac is a small storm and will likely remain small as it moves westward across the tropical Atlantic over the next few days. Such small storms have the capability of strengthening very quickly and weakening just as quickly. By Wednesday, increasing wind shear should lead to weakening as it approaches the Caribbean Sea. Isaac will weaken to a minimal hurricane as it moves near Dominica and Martinique. We cannot rule out the possibility of the system weakening to a tropical storm before reaching the islands. Once in the Caribbean, Isaac is predicted to track a little south of west. Steadily increasing wind shear should weaken Isaac to a remnant low in 6 to 7 days. Currentl y, long-range models do not indicate any threat to the northwest Caribbean or the Gulf of Mexico.

Expected impacts on Land
Central Lesser Antilles: Widespread power outages are expected within about 45 miles of the center, along with moderate structural damage. Flooding and mudslides are likely to cause some damage and travel delays.

Our next advisory will be issued by 10 AM AST / 9 AM CDT.

Meteorologist: Claude Aultman

Forecast Confidence:   Average Hurricane Severity Index
Fcst Hour Valid Lat. Lon. Max Sustained Winds Max Gusts Category Size Intensity Total
0 3AM CDT Mon Sep 10 14.60N 42.60W 75 mph 90 mph Category 1 3 5 8
24 3AM CDT Tue Sep 11 15.10N 48.50W 85 mph 105 mph Category 1 3 6 9
48 3AM CDT Wed Sep 12 15.30N 54.40W 90 mph 110 mph Category 1 3 7 10
60 3PM CDT Wed Sep 12 15.50N 57.00W 85 mph 105 mph Category 1 3 6 9
72 3AM CDT Thu Sep 13 15.70N 59.80W 75 mph 90 mph Category 1 3 5 8
78 9AM CDT Thu Sep 13 15.80N 61.50W 75 mph 90 mph Category 1 3 5 8
84 3PM CDT Thu Sep 13 15.80N 63.20W 70 mph 85 mph Tropical Storm 2 4 6
96 3AM CDT Fri Sep 14 15.80N 65.80W 60 mph 75 mph Tropical Storm 2 3 5
108 3PM CDT Fri Sep 14 15.60N 68.60W 45 mph 60 mph Tropical Storm 1 2 3
120 3AM CDT Sat Sep 15 15.50N 71.50W 40 mph 45 mph Tropical Storm 1 1 2
144 3AM CDT Sun Sep 16 15.50N 75.50W 35 mph 45 mph Remnant Low 0 1 1

The yellow cone represents track error from the previous five hurricane seasons. Over the past five hurricane seasons, the center of the storm tracked within the yellow cone 75% of the time. The cone does not represent the forecast uncertainty in the current advisory for this storm. In addition, hurricane-force winds, very high tides, large waves, and heavy rainfall can often extend well outside the yellow cone.