Update 3:48 p.m.: Otto has become the seventh hurricane of the 2016 season with 75 mph winds.
National Hurricane Center forecasters said the storm has become more symmetric, with a large area of intense thunderstorms near the center.
The storm is forecast to reach 90 mph winds before hitting somewhere in Costa Rica or Nicaragua on Thursday. If Otto makes landfall in Costa Rica, it will be the first time the Central American nation has had a direct hit from a hurricane.
Update 12:45 p.m.: The National Hurricane Center has issued a special advisory alerting that Tropical Storm Otto is expected to become a hurricane later today.
A hurricane watch is in effect for the border of Costa Rica and Panama to Bluefields, Nicaragua.
Otto has sustained 70 mph winds that are expected to reach 90 mph – a strong Category 1 storm – by Thursday.
“To impact Costa Rica, it really has to form right where it’s forming now and that doesn’t happen very often,” said James Franklin, chief of the National Hurricane Center’s hurricane specialist unit. “Nicaragua is a fair bit more common.”
If Otto makes landfall in Costa Rica, it will be the first time the Central American nation had a direct hit from a hurricane.
The center of the forecast track has it just off the border of Costa Rica and Nicaragua at 7 a.m. Thursday.
Otto is expected to maintain tropical cyclone strength as it crosses Central America, emerging into the Pacific as a tropical storm.
If it were to disintegrate over land, but reform in the Pacific, it would become Virgil.
Update 10 a.m.: National Hurricane Center forecasters have increased the intensity forecast for Tropical Storm Otto, expecting it to become a strong Category 1 hurricane with 90 mph winds before it hits Central America.
Otto is close to becoming a hurricane with 70 mph winds this morning and satellite images indicate the cloud pattern has become better organized.
The increased intensity forecast means Otto will like remain a tropical cyclone during its trip through Central America, emerging into the Pacific as a tropical storm.
“Land interaction will cause weakening after landfall, but a stronger Otto is less likely to dissipate as quickly over the eastern Pacific,” forecasters wrote this morning.
Otto is forecast to hit somewhere along the Caribbean coasts of Costa Rica or Nicaragua on Thursday.
Previous story: Tropical Storm Otto has increased to 70 mph winds and is expected to become a hurricane Wednesday before hitting the Caribbean coasts of Nicaragua and Costa Rica.
The storm, which is forecast to build to a Category 1 with at least 80 mph winds, is on track to make landfall Thursday and be near the Pacific Coast by early Friday.
Follow the storm on The Palm Beach Post’s interactive tracking map.
Otto is unusual for forming this late in the hurricane season, but it is taking advantage of the ultra-warm waters of the Caribbean and a pocket of atmosphere where there is little wind shear to help tear it apart.
Read: November hurricanes rare, but surprises do happen.
“This is the favored area in November for development,” said Carl Parker, a hurricane expert with The Weather Channel. “The water temps are probably in the mid-80s and when the atmosphere is right, it’s entirely possible to get something going down there.”
The baseline sea surface temperature needed for hurricane formation is 80 degrees.
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As of the 7 a.m. advisory from the National Hurricane Center, Otto was about 335 miles east southeast of Bluefields, Nicaragua and was not moving. It’s minimum central pressure was 986 mb.
A tropical storm watch is in effect for San Andres Island, which is a Colombian coral island in the Caribbean Sea. A tropical storm watch means that tropical storm conditions are possible within the watch area within 48 hours.
Check The Palm Beach Post radar map.
Otto is expected to strengthen over the next 48 hours and begin moving west. Rainfall is a big concern with Otto with forecasters predicting up to 6 inches of rain with this storm. Some areas could get up to 15 inches.
“These rains could result in life-threatening flash floods and mud slides,” hurricane center forecasters wrote. “Additional heaving rainfall may move into portions of Costa Rica Wednesday night into Thursday as the system approaches the coast.”
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