A rare January hurricane forms, could become month’s strongest on record

Hurricane Alex as observed by NASA's MODIS satellite at 10:30am ET Thursday. (credit: NASA)

Hurricane Alex formed south of the Azores on Thursday morning far from the United States, becoming the third January hurricane on record in the Atlantic Ocean and the first in 78 years. By early afternoon it had strengthened to a system with sustained winds of 85mph.

"Remarkably, Alex has undergone the transformation into a hurricane," wrote Richard Pasch, a senior forecaster at the National Hurricane Center, in his discussion of the system. "A distinct eye is present, embedded within a fairly symmetric mass of deep convection. Water vapor imagery shows that the upper-level trough is now west of the cyclone, with divergent flow over the center, indicative of a tropical transition."

Notably, sea surface temperatures near where the storm formed, 31.5°N and 28.4°W, are not anomalously warm. They are, in fact, near normal for January in the northern Atlantic Ocean. However temperatures in the upper troposphere, about 10 to 15km above the surface of the Earth, are about -60 degrees Celsius, substantially colder than normal. This stark temperature gradient has increased the upward pull on warmth and moisture at the surface, helping the hurricane to intensify.

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