Tuesday, September 17, 2019

Hurricane Jerry (2019)

Storm Active: September 17-25

On September 13, a tropical wave located south of the Cape Verde Islands began to produce shower and thunderstorm activity. It moved generally west-northwestward over the following days and merged with another disturbance located to its west-southwest. The resulting system produced a vigorous but elongated area of convection and was slow to organize further. A small low pressure center appeared along the wave axis on September 15. Gradual improvement continued until the system was classified Tropical Depression Ten during the morning of September 17. During the evening, very cold cloud tops exploded throughout the circulation and winds increased. Tropical Depression Ten became Tropical Storm Jerry (though Tropical Depression Ten formed before Tropical Storm Imelda, the latter system strengthened to a tropical storm and stole the "I" name first).

Jerry faced little wind shear and had the advantage of warming ocean waters for strengthening. The only inhibiting factor was a fairly dry atmosphere, but in a low shear environment, cyclones are often able to "wall off" dry air from disrupting their circulations. The cyclone had impressive outflow and nascent banding features by the morning of September 18, with one notable feature arcing northeast from the circulation center. Hence, steady intensification occurred that day. A significant burst of convection occurred near the center that afternoon. This allowed a inner core to develop and winds increased some more overnight, bringing Jerry to hurricane strength on September 19 as it continued its journey west-northwestward. The cyclone peaked that evening as a category 2 hurricane with maximum sustained winds of 105 mph winds and a minimum pressure of 976 mb.

The next day, wind shear out of the northwest increased substantially and destabilized Jerry's core. Thunderstorm activity was pushed to the southeastern side of the circulation and the system quickly weakened. Nevertheless, bands of locally heavy rain swept across the Northern Leeward Islands through the afternoon and early evening as Jerry passed to the north. The cyclone remained on the smaller side so damage was minimal. The circulation fought back some against shear that evening with new deep convection blossoming about the core. However, maximum winds were still decreasing and the system weakened to a tropical storm by September 21. Following a weakness in the subtropical ridge in part created by Hurricane Humberto, Jerry turned toward the northwest that day and north-northwest on the 22nd. During that time, convection fluctuated but shear out of the west or northwest was a constant for the system. As a result, it remained a strong tropical storm.

On September 23, Jerry turned due north as its center became exposed to the west side of its thunderstorm activity. The atmosphere only became more hostile over the next day as drier air was entrained into the circulation from the southwest. Soon, the system's center was little more than a naked swirl of clouds, and weakening commenced by the 24th. The system began to move northeast and approach Bermuda. Fortunately for the island, which had just been hit by Hurricane Humberto last week, there was almost no rain associated with Jerry, and at worst some tropical storm force wind gusts. In fact, lacking convection for over 12 hours, the cyclone was classified post-tropical early on September 25. The center passed near Bermuda late that day, causing minimal impacts.



This image shows Hurricane Jerry approaching the northern Leeward Islands. Even near peak intensity, the effects of shear are evident in the relatively dry western semicircle.



Jerry brought some heavy rain to the northeasternmost Caribbean islands, but did not have major land impacts.

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