Hurricane Lisa (2004)

Hurricane Lisa was a long-lived Cape Verde-type hurricane in the 2004 Atlantic hurricane season. It was the twelfth named storm, as well as the ninth and final hurricane of the season. Lisa formed on September 19 and spent nearly two weeks fluctuating between a tropical depression and a tropical storm while traversing the central Atlantic. It briefly became a hurricane on October 2 in the north Atlantic before weakening and becoming extratropical shortly afterward. It was never a threat to land.

Origins and weakening
The system originated out of a tropical wave that crossed the African coast on September 16. The wave slowly organized as it tracked south of Cape Verde, and it organized enough to be declared Tropical Depression Thirteen on September 19 while to the southwest of Cape Verde. Initially, the system was hindered by significant wind shear from the southwest as a result of the outflow of Hurricane Karl to its west. Nonetheless, on the morning of September 20, the depression organized enough to become Tropical Storm Lisa with maximum sustained winds of 45 mph (70 km/h) as A poorly defined eye featured also began to develop.

After a brief decrease in wind shear, the storm strengthened to a high-end tropical storm with 70 mph (110 km/h) winds and a central pressure of 990 mbar by the morning of on September 21, following an initial track slightly to the north of that of Karl in the central Atlantic. Tracking westward, it began to weaken and become more disorganized as wind shear had increased again; subsequently, Lisa began interacting with a tropical disturbance east of the system.

After absorbing the adjacent disturbance Lisa briefly weakened to a tropical depression before restrengthening to a tropical storm that evening as the shear moderated. The storm maintained its small but distinct low-level circulation as the other disturbance was absorbed by Lisa. At that point, Lisa began to make a turn to the northwest. The intensity fluctuated on September 24 between depression and storm strength as it tracked northwest. Early on September 25, Lisa regained tropical storm intensity, while turning more to the north. The storm gradually gained strength late on September 25 and early in the morning of September 26, reaching a second peak of 65 mph (100 km/h) that morning as shear moderated. However, the combination of an increase in shear from the southwest and the cool wake of Karl to the north weakened Lisa once again. By September 27, Lisa was just a poorly organized low-end tropical storm.

Restrengthening and demise
Despite the fact that conditions remained quite hostile for development, Lisa slowly intensified once again on the 28th. That afternoon, an eye began to reform as it tracked northward. Lisa approached hurricane intensity once again that evening, and held at 70 mph (110 km/h) throughout the day on September 29 as shear subsided somewhat and the sea surface temperatures remained favorable for development. Initially, Lisa did not strengthen into a hurricane at that time. Early on September 30, the storm began to weaken somewhat once again as it tracked once again into the cooler water left behind by Karl.

The weakening trend was short-lived, however. The eye feature redeveloped once again late on the September 30 and Lisa began to restrengthen, despite cooler water as it tracked into higher latitudes, turning somewhat to the northeast due to a southwesterly flow ahead of a trough. The storm strengthened back to just below hurricane intensity on the morning of October 1. Operationally, Lisa was upgraded to a hurricane that afternoon, however, a QuikSCAT pass was re-analyzed and indicated that the surface winds were somewhat overestimated. Early on October 2, Lisa finally became a hurricane with 75 mph (120 km/h) at 40.3°N latitude, while racing northeastward over relatively cool waters of 74°F (23°C). After renaming a hurricane only 12 hours as a hurricane, Lisa weakened back to a tropical storm that afternoon and began to lose tropical characteristics in the north Atlantic over cool waters. The system continued to disorganize itself that evening and by early on October 3, Lisa was declared an extratropical cyclone while still at tropical storm intensity. Shortly thereafter, the system was absorbed by a larger frontal zone.

Impact
Lisa remained in the open Atlantic Ocean and never threatened any land areas. No damage or fatalities were reported.