Hurricane Otto (2010)

Storm Active: October 6-10
On September 28, a tropical wave over the Central Atlantic began to produce an area of showers and thunderstorms. The next day, another tropical wave to its east also began to be monitored for development. The two systems moved west, but the second caught up with the first and the two waves combined on September 30. The combined disturbance produced a wide area of showers and thunderstorms as it moved westnorthwest, but wind shear increased, and the system remained disorganized. A low pressure center began to form in association with the system, and the low deepened as it passed over the Leeward Islands on October 3-5. By October 6, a surface circulation had formed. However, unlike a tropical cyclone, the center of the system had an upper-level low situated above it, rather than an upper level high, and this fact, combined with the limited convection that was only prevalent on the southeast side of the center, resulted in the classification of the system as Subtropical Depression Seventeen early on October 6. Seventeen's convection wrapped around the center the next day, and the winds reached gale force that evening, meriting the naming of the system as Subtropical Storm Otto.

By late on October 6, Otto's winds had rapidly increased, and the cyclone had reached an intensity of 65 mph winds and a pressure of 990 mb. However, the convection remained very sparse throughout the night, and intensity was difficult to judge, although the ragged appearance of the circulation suggested a slight weakening during the morning of October 7. By later in the morning, the upper-level low that had been shearing the circulation weakened, the core had warmed, and a distinct central eyewall had appeared as the system turned northeast. Otto was now a tropical cyclone, and it was officially classified as such at 11:00 am EDT on October 7. Otto's cloud cover continued to increase as it accelerated eastnortheast, and the system strengthened further, becoming a hurricane by October 8. The system reached its peak intensity of 85 mph and a minimum central pressure of 972 mb, before beginning to weaken. The system picked up speed as it moved out to sea, and it became a tropical storm late on October 9. Otto lost most of its central convection and was displaced to the north over the next 12 hours. As a result, the system was extratropical by midmorning on October 10. The cyclone subsequently impacted the Azores with some rain and wind as it weakened, dissipating on October 12.

Otto caused $20 million in damage but no deaths were reported, most damage being caused by flooding in the Caribbean Islands when the cyclone loitered to the north. As much as 17 inches of rain was reported in parts of Puerto Rico over a six day period from October 3-8 (this and similar rainfall reports courtesy of the Hydrometeorological Prediction Center).



Hurricane Otto at peak intensity speeding off into the open Atlantic.



Track of Otto.