Saturday, September 5, 2015

Tropical Storm Grace (2015)

Storm Active: September 5-9

Yet another tropical wave moved off of the coast of Africa on September 3, exhibiting signs of organization shortly thereafter. By the next day, the system developed a vigorous circulation, but lacked a closed circulation. However, as it moved past the Cape Verde Islands to the south on September 5, the disturbance gained enough organization to be classified Tropical Depression Seven. Just a few hours later, Seven intensified into Tropical Storm Grace over the eastern Atlantic. Deep convection remained limited over the next day as dry air tried to invade the circulation, but the system gradually deepened nonetheless through the day of September 6, reaching its peak intensity of 50 mph winds and a central pressure of 1002 mb.

A strong subtropical ridge maintained Grace's rapid westward motion as shear out of the west-southwest began to increase later that day. This shear impeded the outflow and convective banding of Grace, and began to induce weakening during the morning of September 7. The system maintained some deep convection through the morning of September 8, but it lacked any organizational structure; by this time, Grace had weakened to a minimal tropical storm. It weakened further into a tropical depression later that day as it entered a more stable airmass hostile to thunderstorm formation. By the morning of September 9, Grace was little more than a swirl of low clouds. Shortly afterward, it lost closure entirely and degenerated into a tropical wave. Moisture associated with Grace eventually reached the Caribbean islands a few days later.

Grace never exhibited much convective organization, remaining a weak tropical storm (as shown above) for most of its short lifetime.

As with Danny and Erika before it, Grace formed over the east Atlantic but ultimately suffered its demise amidst the harsh El Nino atmospheric conditions of the Caribbean and central Atlantic.

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