A tropical wave that moved over the Atlantic on September 15 began to generate shower activity around the 18th while located a little less than halfway to the Lesser Antilles. This disturbance moved very quickly west over the next few days and its thunderstorms were popping up mainly south of the center. However, on the 21st it developed a well-defined circulation center. By the next morning, the associated convection had enough organization for the system to be classified Tropical Storm Karen. At the time of naming, the center was located just northeast of Tobago.
Karen was highly disorganized as it crossed the southern Windward Islands that day due to strong northeasterly wind shear. Nevertheless, it brought scattered downpours and gusty winds to nearby Caribbean Islands as it traveled west-northwestward. Thunderstorms regenerated near the center of circulation late on the 22nd, but the center lost some definition overnight. In fact, Karen came close to degenerating into an open wave early on the 23rd, when aircraft reconnaissance was unable to identify a well-defined center. In addition, the system weakened to a tropical depression. Despite all this, the broader circulation persisted and Karen came back to life later that day as towering bursts of thunderstorms erupted south of the center. Overnight, it restrengthened to a tropical storm. At the same time, the cyclone turned northward in the wake of Jerry and approached Puerto Rico and the Virgin Islands.
The center of Karen remained difficult to locate that day, in part due to the presence of several small mesovortices rotating about one another inside the broader circulation. This lack of a compact central core prevented significant strengthening, but thunderstorm activity was much more vigorous. Karen passed near eastern Puerto Rico, bringing 5 inches of rain to portions of the island and the nearby Virgin Islands. The cyclone continued steadily northward, though, and quickly emerged into the open western Atlantic. Its motion moved slightly toward the right that day. Despite at least somewhat favorable conditions, Karen did not strengthen, possibly due to an east-west elongation of its center of circulation. Convection continued to occur, but it did so in an amorphous blob, without organized banding structure. As a ridge built to its north, Karen slowed down and veered eastward. Simultaneously, upper-level atmospheric conditions became more hostile. On September 27, the cyclone weakened to a tropical depression as the center lost even more definition. Later that day, it degenerated into a remnant low. The remnants dissipated completely soon after.
The above image shows Tropical Storm Karen near Puerto Rico. Fortunately, the system was relatively weak and moving quickly, sparing the island significant damage.
Karen had organizational issues throughout its life and was ultimately unable to survive the high shear conditions of the western Atlantic.
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