Category 5 hurricanes are tropical cyclones that reach Category 5 intensity on the Saffir–Simpson hurricane scale. They are by definition the strongest hurricanes that can form on planet Earth. They are rare in the northeastern Pacific Ocean and generally form only once every several years. In general, Category 5s form in clusters in single years. Landfalls by such storms are rare due to the generally westerly path of tropical cyclones in the Northern Hemisphere. The term "hurricane" is used for tropical cyclones in the Pacific Ocean, north of the equator and east of the International Date Line. A Category 5 Pacific hurricane is therefore a tropical cyclone in the north Pacific Ocean that reached Category 5 intensity east of the International Date Line. Identical phenomena in the north Pacific Ocean west of the dateline are called "typhoons" or "super typhoons". Category 5 super typhoons generally happen several times per season, so cyclones of that intensity are not exceptional for that region. This difference in terminology therefore excludes storms such as Typhoon Paka and Typhoon Oliwa of 1997, and Typhoon Genevieve of 2014, which formed east of the dateline but did not reach Category 5 intensity until after crossing the dateline. Climatology and statistics The majority of tropical cyclones form and organize in areas of warm sea surface temperatures, usually of at least and low vertical wind shear; however, there are outliers to this general rule, such as storms that manage to intensify despite high amounts of vertical wind shear. When a pre-existing tropical disturbance – usually a tropical wave or a disturbance originating in the Intertropical Convergence Zone – enters an area where the aforementioned conditions are present, the disturbance can develop into a tropical cyclone, provided it is far enough from the equator to experience a sufficiently strong Coriolis force, which causes the counterclockwise rotation of hurricanes in the Northern Hemisphere. Between the months of December and April, sea surface temperatures in the tropics, where most Northeast Pacific tropical cyclones develop, are usually too low to support significant development. Also, the presence of a semi-permanent high-pressure area known as the North Pacific High in the eastern Pacific greatly reduces tropical cyclone development in the winter months, as the North Pacific High results in vertical wind shear that causes environmental conditions to be unconducive to tropical cyclone formation. Another factor preventing tropical cyclones from forming during the winter is the