Meteorological History of Hurricane Gustav - Dissipation

Dissipation

After landfall the hurricane continued moving northwestward at 15 mph (24 km/h). The mid-level ridge over the southeastern United States which had dominated Gustav's steering for the last few days drifted northward, pulling the hurricane with it. Moving further inland Hurricane Gustav continued to weaken while delivering torrential rains to the central gulf coast of the United States. The eye that had cleared during landfall filled in that afternoon and was replaced by a central dense overcast. That night, 12 hours after landfall, Gustav weakened to a tropical storm with winds of 60 mph (97 km/h).

Slipping below tropical storm strength the following morning, Gustav's previously firm steering currents began to erode and its forward motion slowed. As the storm crept through northwest Louisiana on September 2, its heavy rainfall began to accumulate in the region. As the storm continued northwestward though the intersection of Arkansas, Louisiana, Texas, and Oklahoma and into Arkansas proper, its forward motion slowed considerably and it dumped isolated rainfall accumulations in excess of 9 inches (228.60 mm). Through the morning of September 3, Tropical Depression Gustav briefly drifted north-northeastward under very weak steering currents, but stalled completely over southwestern Arkansas that afternoon and spread heavy rain into the mid-Mississippi Valley. By the evening, steering currents returned and Gustav picked up speed to the northeast at 7 mph (11 km/h). Moving even more rapidly Gustav left the Mississippi Valley and headed towards the Ohio Valley.

The next morning, as it passed through Missouri, Gustav began to gain extratropical characteristics as it merged with a frontal boundary. The extratropical transition was completed on the afternoon of September 4 as Gustav's remnant low was moving 28 mph (45 km/h) over St. Louis, Missouri. Although no longer a tropical system, the remnants of Gustav continued to bring wind and rain to the northern United States. That evening, still traveling northeastward, the remnants dropped 2–4 in (51–100 mm) of rain on Illinois and its widespread remnant low produced trace rainfall stretching from Iowa to Indiana. By nightfall on September 4 the remnants had reached southwest Michigan, where they dumped rain until the next morning, with accumulations as high as 5 in (130 mm). The storm's circulation remained intact through Wisconsin where it dropped almost 1 in (25 mm) of rainfall. Some of Gustav's more northerly remnants even drifted into Minnesota where they dropped small amounts of rain. On September 5, the storm's extratropical remnants were absorbed by a larger extratropical low moving through the Great Lakes.