Visible satellite image over Tropical Depression 12 from 8am EDT today. (NASA)

Tropical Storm Kate is dousing parts of the Bahamas with heavy rain and strong winds this week, and could intensify into the season’s fourth hurricane by Wednesday. It’s the first tropical cyclone to impact the Bahamas in November in five years.

Hurricane Hunters flew into then-Tropical Depression Twelve early Monday morning to find a strengthening storm, and the National Hurricane Center upgraded the system to Tropical Storm Kate. The storm’s maximum sustained winds are 40 mph, and it’s centered about 350 miles east-southeast of Miami.

Since the cyclone formed Sunday night, it has gradually become better organized as it sits over the warm waters of the Bahamas. Tropical storm warnings are in effect for the central and western Bahamas, though it is forecast to turn northeast away from the U.S. and track out to sea.

[The Northern Hemisphere’s record-shattering tropical cyclone season, by the numbers]

Kate is the latest named storm since Tropical Storm Melissa on Nov. 18, 2013.

114915W5_NL_sm Track and intensity forecast for Tropical Storm Kate on Monday morning. (National Hurricane Center)

The low pressure disturbance from which Kate formed has been trekking across the Atlantic Ocean for about a week prior to its intensification over warm Bahamas water. Now that it’s named, has just a couple days left before it gets absorbed by an approaching trough of low pressure.

Forecast models are in excellent agreement on a track similar to the Hurricane Center’s official forecast, and the intensity forecast is also “relatively” easy. The storm is over very warm sea surface temperatures, very low vertical wind shear and moderate low-level humidity, so environmental conditions favor additional intensification at least through Wednesday.

Kate will likely peak at a strong tropical storm — or possibly reach weak Category 1 hurricane status — on Wednesday, after which the environment will become quite hostile to a tropical cyclone, and the storm will lose its tropical characteristics.

On average by this date, roughly 95 percent of the season’s activity has occurred, with the official end of the Atlantic hurricane season coming up on Nov. 30. As was predicted by groups that make seasonal forecasts of tropical cyclone activity, this season was significantly less active than an average season, largely due to the very strong El Niño taking place in the Pacific Ocean.

Through Monday, we have had 11 named storms, three hurricanes, and two  major hurricanes (Category 3 or stronger). Those numbers aren’t too far off of the average, but overall, the storms were short-lived which resulted in overall seasonal activity that’s just 57 percent of average, to-date, measured by accumulated cyclone energy, which combines all of the intensity and longevity of all of the storms.


Timeline of total accumulated cyclone energy for an average season (purple) and for 2015 (yellow).