On October 30, a poorly-defined tropical wave moved off the coast of Africa with little thunderstorm activity.
At this point in the season, tropical waves are uncommon due to increasingly unfavourable conditions, making the origins of Kate "rare, but not unprecedented" as described by the National Hurricane Center (NHC) in its post-season report on the storm.
Traversing through the eastern Atlantic in unfavourable conditions, the disorganised disturbance failed to organise any further.
By November 5, however, as the wave approached the Lesser Antilles, a low-level vorticity split from the wave and traveled to the west-northwest, while the tropical wave headed towards Central America.
The new disturbance then turned towards Hispaniola and Puerto Rico, at which point the National Hurricane Center began to monitor the disturbance for possible tropical cyclogenesis.
On November 7, convection increased as it passed to the northeast of Hispaniola; however, surface pressures were still relatively high.
By early on November 8, showers and convection became more concentrated around the area of low pressure, and there was indications that the disturbance was producing gale-force winds in squally bands that were short-lived.
It is estimated that Tropical Depression Twelve formed at around 18:00 UTC, after further organization occurred, while located north of the Turks and Caicos Islands.
The depression moved to the west in response to an area of high pressure that was situated to its north.
Banding features began to develop along with a defined outflow pattern, and after an Air Force reconnaissance aircraft investigated the system on November 9, the depression was upgraded to Tropical Storm Kate at 15:00 UTC that day.

The overall size of Kate was initially relatively small, with a compact central dense overcast (CDO) extending only 40 miles (64 km) from the center of the storm.
Kate continued to move to the west-northwest while steadily strengthening, and later made its closest approach to The Bahamas on November 9 – passing about 15 miles (24 km) from Cat Island.
However, observations reported that the circulation of Kate was very small and did not register in some of the operating stations.
By the early morning hours of November 10, Kate began to turn to the north in response to a trough that was coming off the East Coast of the United States.
Shortly thereafter, Kate strengthened to just below hurricane intensity with winds of 70 mph (110 km/h), and was initially predicted to become a hurricane shortly thereafter before passing over cooler sea surface temperatures, however intensification briefly halted.
By 00:00 UTC on November 11, Kate had intensified into a hurricane as it began to accelerate northeast into and become embedded into the mid-latitude westerlies, after a microwave pass revealed banding features had become more defined near the center.
This made it the latest-forming hurricane in the Atlantic basin since Hurricane Epsilon in 2005.
Shortly afterwards, Kate reached its peak intensity with winds of 85 mph (140 km/h) and a pressure of a 980 millibars (29 inHg) based on continued improvement of its satellite presentation.
Afterwards, colder waters and increasing wind shear caused Kate to weaken, and it transitioned into an extratropical cyclone by 00:00 UTC on November 12.
The remnants of Kate continued to accelerate over the North Atlantic Ocean for another day before slowing down dramatically and turning eastwards before being absorbed by a larger cyclone on November 13.
On October 30, a poorly-defined tropical wave moved off the coast of Africa with little thunderstorm activity. At this point in the season, tropical waves are uncommon due to increasingly unfavourable conditions, making the origins of Kate "rare, but not unprecedented" as described by the National Hurricane Center (NHC) in its post-season report on the storm. Traversing through the eastern Atlantic in unfavourable conditions, the disorganised disturbance failed to organise any further. By November 5, however, as the wave approached the Lesser Antilles, a low-level vorticity split from the wave and traveled to the west-northwest, while the tropical wave headed towards Central America. The new disturbance then turned towards Hispaniola and Puerto Rico, at which point the National Hurricane Center began to monitor the disturbance for possible tropical cyclogenesis. On November 7, convection increased as it passed to the northeast of Hispaniola; however, surface pressures were still relatively high. By early on November 8, showers and convection became more concentrated around the area of low pressure, and there was indications that the disturbance was producing gale-force winds in squally bands that were short-lived. It is estimated that Tropical Depression Twelve formed at around 18:00 UTC, after further organization occurred, while located north of the Turks and Caicos Islands. The depression moved to the west in response to an area of high pressure that was situated to its north. Banding features began to develop along with a defined outflow pattern, and after an Air Force reconnaissance aircraft investigated the system on November 9, the depression was upgraded to Tropical Storm Kate at 15:00 UTC that day.
The overall size of Kate was initially relatively small, with a compact central dense overcast (CDO) extending only 40 miles (64 km) from the center of the storm. Kate continued to move to the west-northwest while steadily strengthening, and later made its closest approach to The Bahamas on November 9 – passing about 15 miles (24 km) from Cat Island. However, observations reported that the circulation of Kate was very small and did not register in some of the operating stations. By the early morning hours of November 10, Kate began to turn to the north in response to a trough that was coming off the East Coast of the United States. Shortly thereafter, Kate strengthened to just below hurricane intensity with winds of 70 mph (110 km/h), and was initially predicted to become a hurricane shortly thereafter before passing over cooler sea surface temperatures, however intensification briefly halted. By 00:00 UTC on November 11, Kate had intensified into a hurricane as it began to accelerate northeast into and become embedded into the mid-latitude westerlies, after a microwave pass revealed banding features had become more defined near the center. This made it the latest-forming hurricane in the Atlantic basin since Hurricane Epsilon in 2005. Shortly afterwards, Kate reached its peak intensity with winds of 85 mph (140 km/h) and a pressure of a 980 millibars (29 inHg) based on continued improvement of its satellite presentation. Afterwards, colder waters and increasing wind shear caused Kate to weaken, and it transitioned into an extratropical cyclone by 00:00 UTC on November 12. The remnants of Kate continued to accelerate over the North Atlantic Ocean for another day before slowing down dramatically and turning eastwards before being absorbed by a larger cyclone on November 13.
Hurricane Kate (2015)