Sunday, August 13, 2017

Hurricane Gert (2017)

Storm Active: August 12-

On August 2, a vigorous tropical wave left Africa and moved westward over the Atlantic Ocean. While environmental conditions seemed conducive for development, the system was unable to consolidate. Dry air interfered with the production of deep convection, and the associated circulation remained highly elongated. Competing vortices on the northeast and southwest sides vying for dominance cost the wave the chance to organize over the next several days. By August 7, conditions had become unfavorable due to the presence of an upper-level low to the northeast. Nevertheless, the system proceeded steadily west-northwestward, passing a bit north of the Lesser Antilles on August 10. Wind shear diminished and the wave encountered more humid air soon after, giving it another chance at development. Convection increased and the circulation became better defined over the next two days, and Tropical Depression Eight finally formed late on August 12.

The system was experiencing some wind shear out of the north, but conditions were otherwise supportive of intensification. August 13 saw the naming of Tropical Storm Gert when the system lay well east of the Florida coastline and was turning toward the north. The inner core structure improved considerably that night and into August 14. The first hints of an eye appeared that afternoon, and Gert was upgraded to a hurricane that night. The cyclone then began to feel the influence of a frontal system moving off of the U.S. east coast, and turned northeast on August 15, accelerating as it did so. Even as it gained latitude, Gert still took advantage of warm Gulf Stream waters to continue strengthening. A compact eye feature became apparent on both visible and satellite imagery by the morning of the 16th.

As of 11:00 am EDT on August 16, 2017, Hurricane Gert had maximum winds of 90 mph, a central pressure of 975 mb and was moving to the northeast at 25 mph.

Monday, August 7, 2017

Hurricane Franklin (2017)

Storm Active: August 6-10

Towards the end of July, a tropical wave tracked westward across the central Atlantic, showing some potential for development as it produced scattered showers and thunderstorms. Dry air and deteriorating atmospheric conditions stifled this potential by the time August had begun. Nevertheless, the tropical wave continued into the Caribbean. Significant convection flared up near the system on August 3 when it was located in the eastern Caribbean, and surface pressures began to slowly decline in the area. For the next day or two, however, it was contending with very high wind shear, and was unable to organize much. This changed early on August 5, when thunderstorm activity concentrated near its nascent circulation. Meanwhile, shear began to decline, allowing the system to take advantage of quite warm sea water. Late on August 6, Tropical Storm Franklin was named northeast of Honduras.

Franklin's environment steered it steadily west-northwest the following day. Its banding features steadily improved, resulting in steady strengthening. By that afternoon, its sustained winds had increased to 60 mph and its pressure had dropped to 999 mb. However, dry air infiltrated the circulation from the south that evening, weakening thunderstorm activity near the center and preventing additional intensification before Franklin made landfall that evening in the Yucatan Peninsula. The cyclone weakened over land into August 8, but the low-lying land did not disrupt the core much, and the system remained well-organized. Late in the afternoon, the center of circulation emerged over the Bay of Campeche and assumed a more westward trajectory. Strong outer bounds quickly formed and Franklin's core also quickly improved over the very warm ocean water. The following day saw the system intensify from a minimal tropical storm to a category 1 hurricane by the afternoon of August 9. It strengthened a bit further to its peak intensity of 85 mph winds and a pressure of 981 mb before making landfall in Mexico. Franklin's decay was swift over the mountainous terrain, and it dissipated by late morning on August 10.

The remnants of Franklin crossed over into the eastern Pacific Ocean over the next day and quickly reorganized over water. Late on August 11, they regenerated into a tropical storm. Since the system dissipated before reforming in another basin, it received a separate name from the Eastern Pacific name list: Jova.

The above image shows Hurricane Franklin at peak intensity just before landfall in Mexico.

Franklin strengthened quickly over the warm waters of the Bay of Campeche.