Tuesday, September 20, 2016

Tropical Storm Lisa (2016)

Storm Active: September 19-24

On September 16, a tropical wave moved off of Africa into quite favorable conditions in the eastern Atlantic. As a result, an area of low pressure developed almost immediately and an impressively broad circulation developed. After initially having some trouble consolidating, the circulation became well-defined on September 19 and the system was classified Tropical Depression Thirteen. Shortly after formation, the depression took a west-northwest turn toward a weakness in the ridge to its north. Steady organization followed over the next 24 hours as the system strengthened into Tropical Storm Lisa during the morning of September 20 and then experienced more strengthening through that evening.

Due to the presence of an upper-level low pressure system located to the northwest of Lisa, shear out of the west and southwest began to increase dramatically on September 21, gradually exposing the center of circulation as convection retreated to the east. Lisa held its own, however, continuing to produce very deep convective bursts. It even rebounded from a momentary weakening that day by strengthening to its peak intensity of 50 mph winds and a pressure of 999 mb during the morning of September 22. There was evidence by this point that the circulation was becoming elongated in response to the continued shear. Meanwhile, thunderstorm activity began to wane and Lisa weakened through the rest of the day and overnight.

The storm experienced once last resurgence of thunderstorms during the morning of the 24th and in fact was upgraded back to tropical storm status as a result. However, this was only a temporary reprieve. By that afternoon, the circulation was entirely bare. Lisa was downgraded to a tropical depression that afternoon and a remnant low that night. The circulation produced shower activity for an additional few days before dissipation.

The image shows a disorganized Lisa over the eastern Atlantic.

A break in the ridge to Lisa's north allowed it to veer north quite far east and encounter hostile atmospheric conditions quite quickly.

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