Tropical Storm Isaac Track Chart, Advisory #9
 

Current Location: 14.6N, 40.1W
Geographic Reference: 1400 miles east of Martinique
Movement: West at 16 mph
Max Winds: 65 mph gusting to 75 mph
Current Hurricane Severity Index: 5 out of a possible 50 points (2 size, 3 intensity)
Max Predicted Hurricane Severity Index: 9 out of a possible 50 points (3 size, 6 intensity)
Current Radius of Tropical Storm-Force Winds: 45 miles
Max Predicted Radius of Tropical Storm-Force Winds: 65 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 is a tiny storm, somewhat similar to hurricane Beryl which formed back in July. The whole storm is barely 120 miles across, if that. Such small storms have the capability of strengthening very quickly – and weakening just as quickly. We think that Isaac will strengthen to a hurricane over the next 24 hours or so as it moves almost due west in the open Atlantic. By Wednesday, increasing wind shear should lead to weakening as it approaches the Caribbean Sea. It is possible that Isaac will weaken to a tropical storm as it moves past Martinique early on Thursday morning.

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 5-6 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 10 PM AST / 9 PM CDT.

Meteorologist: Chris Hebert

Forecast Confidence:   Average Hurricane Severity Index
Fcst Hour Valid Lat. Lon. Max Sustained Winds Max Gusts Category Size Intensity Total
0 3PM CDT Sun Sep 09 14.60N 40.10W 65 mph 75 mph Tropical Storm 2 3 5
24 3PM CDT Mon Sep 10 15.00N 45.70W 75 mph 85 mph Category 1 3 5 8
48 3PM CDT Tue Sep 11 15.40N 52.00W 85 mph 100 mph Category 1 3 6 9
72 3PM CDT Wed Sep 12 15.50N 58.30W 80 mph 90 mph Category 1 3 5 8
84 3AM CDT Thu Sep 13 15.70N 61.80W 70 mph 80 mph Tropical Storm 2 4 6
96 3PM CDT Thu Sep 13 15.90N 64.80W 60 mph 75 mph Tropical Storm 2 3 5
108 3AM CDT Fri Sep 14 15.80N 68.40W 45 mph 60 mph Tropical Storm 1 2 3
120 3PM CDT Fri Sep 14 15.70N 72.30W 35 mph 45 mph Remnant Low 0 1 1
144 3PM CDT Sat Sep 15 14.90N 78.40W 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.