The first subtropical depression of the 2017 Atlantic Hurricane season, which doesn’t officially start until June 1, has formed.
Other than to shipping lanes in the central Atlantic, this system should not be a bother to anyone. The center of Subtropical Depression One was located near latitude 31.9 North, longitude 40.9 West in its initial advisory today. The subtropical depression is moving toward the north-northeast near 8 mph and a gradual turn to the north is expected tonight. Maximum sustained winds are near 35 mph ith higher gusts. Little change in strength is forecast today, and the subtropical depression is forecast to become absorbed by a large extratropical low on Thursday. The estimated minimum central pressure is 995 mb (29.39 inches).
The Florida-based National Hurricane Center began naming subtropical storms in 2002. Between 1968 and 2001, subtropical storms were simply given numbers such as “One” or “Two.” Before 1968, subtropical storms were never classified as such. A subtropical storm system is a non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal, synoptic-scale cyclones that originate over tropical or subtropical waters, and have a closed surface wind circulation about a well-defined center. In addition, they have organized moderate to deep convection, but lack a central dense overcast. Unlike tropical cyclones, subtropical cyclones derive a significant proportion of their energy from baroclinic sources, and are generally cold-core in the upper troposphere, often being associated with an upper-level low or trough. In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center and generally have a less symmetric wind field and distribution of convection.
In the case of Subtropical Depression #1, it is not expected to strengthen to Subtropical Storm status prior to being absorbed by the extratropical low in the Atlantic.