 Tropical cyclones that occur within the Northern Hemisphere to the east of the anti-meridian, are officially monitored by either the National Hurricane Center or the Central Pacific Hurricane Center. Within the region a tropical cyclone is defined to be a warm cored, non-frontal synoptic cyclone, that develops over tropical or subtropical waters, with organized atmospheric convection and a closed well defined circulation centre. The region also defines a subtropical cyclone as a non-frontal low pressure system, that has the characteristics of both tropical and extratropical cyclones. Once either of these classifications are met then the warning centers will classify the system as either a tropical or subtropical depression, if the one-minute sustained winds estimated or measured as less than 33 kn (38 mph; 62 km / h). Should the system intensify further or already have one-minute sustained winds of 34 – 63 kn (39 – 73 mph; 63 – 118 km / h), then it will be called either a tropical or subtropical storm and assigned a name. Should the tropical system further intensify and have winds estimated or measured, as greater than 64 kn (74 mph; 119 km / h), then it will be called a hurricane and classified on the Saffir-Simpson hurricane wind scale. The lowest classification on the SSHWS is a Category 1 hurricane, which has winds of between 64 – 82 kn (74 – 95 mph, 119 – 153 km / h). Should the hurricane intensify further then it will be rated as a Category 2 hurricane, if it has winds of between 83 – 95 kn (96 – 110 mph, 154 – 177 km / h). When a system becomes a Category 3 hurricane with winds of between 96 – 112 kn (111 – 129 mph, 178 – 208 km / h), it is considered to be a major hurricane by the warning centers. A Category 4 hurricane has winds of 113 – 136 kn (130 – 156 mph, 209 – 251 km / h), while a Category 5 hurricane has winds of above 137 kn (157 mph, 252 km / h).
