The structure of Subtropical Storm Alex evolved into the structure associated with a tropical cyclone and the National Hurricane Center reclassified it as Hurricane Alex on Thursday morning. At 10:00 a.m. EST on Thursday the center of Hurricane Alex was located at latitude 31.5°N and longitude 28.4°W which put it about 490 miles (790 km) south of Faial in the Central Azores. Alex was moving toward the north at 20 m.p.h. (32 km/h). The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 105 m.p.h. (170 km/h). The minimum surface pressure was 981 mb.
A Hurricane Warning has been issued for Faial, Pico, Sao Jorge, Graciosa, and Terceira in the Central Azores. A Tropical Storm Warning has been issued for Sao Miguel and Santa Maria in the Eastern Azores.
Alex has developed the structure associated with a small hurricane. An eye is clearly visible on satellite imagery. A ring of thunderstorms surrounds the eye and there are spiral bands rotating around the core of the circulation. Latent energy released by convection around the core of Hurricane Alex generated a warm core in the middle and upper troposphere. That convection is also generating upper level divergence which is pumping out mass, especially to the north and east of the center.
Hurricane Alex is over water where the Sea Surface Temperatures (SSTs) are near 20.5°C. Those SSTs are usually considered to be too cold to supply enough energy to promote the development of a hurricane. However, it is January and the temperatures in the middle and upper troposphere are also cold. So, there is clearly enough instability to generate convection and create a hurricane. The thunderstorms are in Alex are not as tall as they would be if the SSTs are warmer. The shorter thunderstorms do not extend into the stronger winds in the upper troposphere and Hurricane Alex is not experiencing as much vertical wind shear as might be expected. The combination of more instability and less vertical wind shear allowed Alex to transition from a subtropical storm to a hurricane.
The upper level divergence could allow Alex to intensify a little more during the next 12 hours. Hurricane Alex will move over SSTs that are even colder and at some point the structure of Alex will change again. It will develop fronts and transition into an extratropical cyclone.
Alex is being steered northward by an upper level trough to its west and that general motion is expected to continue for the next several days. On its anticipated track Hurricane Alex will move over portions of the Azores on Friday.
The Hurricane Intensity Index (HII) for Alex is 12.7. The Hurricane Size Index is (HSI) 7.0. The Hurricane Wind Intensity Size Index (HWISI) is 19.7. Those indices suggest that Hurricane Alex is capable of causing localized minor damage with isolated areas of serious damage.
Alex is the first Atlantic hurricane to form during the month of January since 1938. Alex is the first tropical cyclone be a hurricane in January since Hurricane Alice in 1955.