About Hurricane Center

The National Hurricane Center (NHC) is the division of the United States' National Weather Service responsible for tracking and predicting tropical weather systems between the Prime Meridian and the 140th meridian west poleward to the 30th parallel north in the northeast Pacific Ocean and the 31st parallel north in the northern Atlantic Ocean. The agency, which is co-located with the Miami branch of the National Weather Service, is situated on the campus of Florida International University in University Park, Florida.

The NHC's Tropical Analysis and Forecast Branch (TAFB) routinely issues marine forecasts, in the form of graphics and high seas forecasts year round, with the Ocean Prediction Center having backup responsibility for this unit. The Technology and Science Branch (TSB) provides technical support for the center, which includes new infusions of technology from abroad. The Chief, Aerial Reconnaissance Coordination, All Hurricanes (CARCAH) unit tasks planes, for research and operational purposes, to tropical cyclones during the Atlantic hurricane season and significant weather events, including snow storms, during winter and spring. Research to improve operational forecasts is done through the Hurricane Forecast Improvement Project (HFIP) and Joint Hurricane Test Bed (JHT) initiatives.

During the Atlantic and northeast Pacific hurricane seasons, the Hurricane Specialists Unit (HSU) issues routine tropical weather outlooks for the northeast Pacific and northern Atlantic oceans. When tropical storm or hurricane conditions are expected within 48 hours, the center issues watches and warnings via the news media and National Oceanic and Atmospheric Administration (NOAA) Weather Radio.

Although the NHC is an agency of the United States, the World Meteorological Organization has designated it as the Regional Specialized Meteorological Center for the North Atlantic and eastern Pacific, making it the clearinghouse for tropical cyclone forecasts and observations occurring in these areas. If the NHC loses power or becomes incapacitated, the Central Pacific Hurricane Center backs tropical cyclone advisories and tropical weather outlooks for the northeast Pacific Ocean while the Weather Prediction Center backs up tropical cyclone advisories and tropical weather outlooks for the North Atlantic Ocean.

The National Hurricane Research Project, begun in the 1950s, used aircraft to study tropical cyclones and carry out experiments on mature hurricanes through its Project Stormfury. On July 1, 1956, a National Hurricane Information Center was established in Miami, Florida, which became a warehouse for all hurricane-related information from one United States Weather Bureau office. The Miami Hurricane Warning Office (HWO) moved from Lindsey Hopkins Hotel to the Aviation Building 4 miles (6.4 km) to the northwest on July 1, 1958. Forecasts within the hurricane advisories were issued one day into the future in 1954 before being extended to two days into the future in 1961, three days into the future in 1964, and five days into the future in 2001.The Miami HWO moved to the campus of the University of Miami in 1964, and was referred to as the NHC in 1965

For general questions and information about the NHC or its branches please contact:

  National Hurricane Center
 11691 S.W. 17th Street
 Miami, Florida 33165
(305) 229-4470

NOAA Public Affairs Officer:

NHC Public Affairs
nhc.public.affairs@noaa.gov
 (305) 229-4404

How does a hurricane form (Full Report)

Hurricanes are the most violent storms on Earth. They form near the equator over warm ocean waters. Actually, the term hurricane is used only for the large storms that form over the Atlantic Ocean or eastern Pacific Ocean.

The generic, scientific term for these storms, wherever they occur, is tropical cyclone. Other names they are given, depending on where in the world they are born, are typhoons, cyclones, severe tropical cyclones, or severe cyclonic storms. Whatever they are called, the same forces and conditions are at work in forming these giant storms, any of which can cause damage or devastation when they hit land where people live.

Tropical cyclones are like engines that require warm, moist air as fuel. So the first ingredient needed for a tropical cyclone is warm ocean water. That is why tropical cyclones form only in tropical regions where the ocean is at least 80 degrees F for at least the top 50 meters (about 165 feet) below the surface.

The second ingredient for a tropical cyclone is wind. In the case of hurricanes that form in the Atlantic Ocean, the wind blowing westward across the Atlantic from Africa provides the necessary ingredient. As the wind passes over the ocean's surface, water evaporates (turns into water vapor) and rises. As it rises, the water vapor cools, and condenses back into large water droplets, forming large cumulonimbus clouds. These clouds are just the beginning.

Meteorologists have divided the development of a tropical cyclone into four stages: Tropical disturbance, tropical depression, tropical storm, and full-fledged tropical cyclone.

Tropical disturbance

When the water vapor from the warm ocean condenses to form clouds, it releases its heat to the air. The warmed air rises and is pulled into the column of clouds. Evaporation and condensation continue, building the cloud columns higher and larger. A pattern develops, with the wind circulating around a center (like water going down a drain). As the moving column of air encounters more clouds, it becomes a cluster of thunderstorm clouds, called a tropical disturbance.

 Tropical depression 

As the thunderstorm grows higher and larger, the air at the top of the cloud column is cooling and becoming unstable. As the heat energy is released from the cooling water vapor, the air at the top of the clouds becomes warmer, making the air pressure higher and causing winds to move outward away from the high pressure area. This movement and warming causes pressures at the surface to drop. Then air at the surface moves toward the lower pressure area, rises, and creates more thunderstorms. Winds in the storm cloud column spin faster and faster, whipping around in a circular motion. When the winds reach between 25 and 38 mph, the storm is called a tropical depression.

Tropical storm

When the wind speeds reach 39 mph, the tropical depression becomes a tropical storm. This is also when the storm gets a name. The winds blow faster and begin twisting and turning around the eye, or calm center, of the storm. Wind direction is counterclockwise (west to east) in the northern hemisphere and clockwise (east to west) in the southern hemisphere. This phenomenon is known as the Coriolis effect.

Tropical cyclone 

When the wind speeds reach 74 mph, the storm is officially a tropical cyclone. The storm is at least 50,000 feet high and around 125 miles across. The eye is around 5 to 30 miles wide. The trade winds (which blow from east to west) push the tropical cyclone toward the west—toward the Caribbean, the Gulf of Mexico, or the southeastern coast of the U.S. The winds and the low air pressure also cause a huge mound of ocean water to pile up near the eye of the tropical cyclone, which can cause monster storm surges when all this water reaches land.

Tropical cyclones usually weaken when they hit land, because they are no longer being fed by the energy from the warm ocean waters.

However, they often move far inland, dumping many inches of rain and causing lots of wind damage before they die out completely.