Current Location: 14.6N, 41.3W
Geographic Reference: 1315 miles east of Martinique
Movement: West at 14 mph
Max Winds: 70 mph gusting to 85 mph
Current Hurricane Severity Index: 6 out of a possible 50 points (2 size, 4 intensity)
Max Predicted Hurricane Severity Index: 10 out of a possible 50 points (3 size, 7 intensity)
Current Radius of Tropical Storm-Force Winds: 45 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 early on Thursday morning.
2. Weakening is expected in the Caribbean due to strong wind shear.
Our Forecast
Isaac remains 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. We think that Isaac will strengthen to a hurricane within the next 12 hours as it moves just north of due west. By Wednesday, increasing wind shear should lead to weakening as it approaches the Caribbean Sea. It is possible that 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. Currently, 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 4 AM AST / 3 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 | 9PM CDT Sun Sep 09 | 14.60N | 41.30W | 70 mph | 85 mph | Tropical Storm | 2 | 4 | 6 |
| 24 | 9PM CDT Mon Sep 10 | 15.00N | 47.30W | 85 mph | 105 mph | Category 1 | 3 | 6 | 9 |
| 48 | 9PM CDT Tue Sep 11 | 15.20N | 53.30W | 90 mph | 110 mph | Category 1 | 3 | 7 | 10 |
| 60 | 9AM CDT Wed Sep 12 | 15.40N | 56.30W | 85 mph | 105 mph | Category 1 | 3 | 6 | 9 |
| 72 | 9PM CDT Wed Sep 12 | 15.60N | 59.30W | 80 mph | 100 mph | Category 1 | 3 | 5 | 8 |
| 78 | 3AM CDT Thu Sep 13 | 15.70N | 61.10W | 75 mph | 90 mph | Category 1 | 3 | 5 | 8 |
| 84 | 9AM CDT Thu Sep 13 | 15.70N | 62.80W | 75 mph | 90 mph | Category 1 | 3 | 5 | 8 |
| 96 | 9PM CDT Thu Sep 13 | 15.90N | 65.70W | 65 mph | 80 mph | Tropical Storm | 2 | 3 | 5 |
| 108 | 9AM CDT Fri Sep 14 | 15.70N | 69.00W | 50 mph | 65 mph | Tropical Storm | 1 | 2 | 3 |
| 120 | 9PM CDT Fri Sep 14 | 15.50N | 72.20W | 40 mph | 45 mph | Tropical Storm | 1 | 1 | 2 |
| 144 | 9PM CDT Sat Sep 15 | 15.50N | 77.90W | 30 mph | 40 mph | Remnant Low | 0 | 0 | 0 |
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.
