Pacific hurricane

This separation between the two basins has a practical convenience, however, as tropical cyclones rarely form in the central north Pacific due to high vertical wind shear, and few cross the dateline.

Documentation of Pacific hurricanes dates to the Spanish colonization of Mexico, when the military and missions wrote about "tempestades".

After observing the rotating nature of tropical cyclones, meteorologist William Charles Redfield expanded his study to include storms in the eastern North Pacific Ocean in the middle of the 19th century.

Between June and October 1850, Redfield observed five tropical cyclones along "the southwestern coast of North America", along with one in each of the three subsequent years.

By around 1920, Pacific hurricanes were officially recognized due to widespread ship observations, radio service, and a newly created weather network in western Mexico.

[11] The archives format was significantly changed during 2013 to include non-synoptic best track times, non-developing tropical depressions and wind radii.

A second factor preventing tropical cyclones from forming during the winter is the occupation of a semi-permanent low-pressure area designated the Aleutian Low between January and April.

In addition, its effects in the central Pacific near 160° W causes tropical waves that form in the area to drift northward into the Gulf of Alaska and dissipate.

During El Niño events, sea surface temperatures increase in the Northeast Pacific and vertical wind shear decreases.

The RSMC monitors the eastern Pacific and issues reports, watches and warnings about tropical weather systems and cyclones as defined by the World Meteorological Organization.

[20] Most east Pacific hurricanes originate from a tropical wave that drifts westward across the intertropical convergence zone, and across northern parts of South America.

If wind shear is low, a tropical cyclone can undergo rapid intensification as a result of very warm oceans, becoming a major hurricane.

Sometimes storms can move north-east either across Central America or mainland Mexico and possibly enter the Caribbean Sea becoming a North Atlantic hurricane, but these are rare.

[17] The Central Pacific Hurricane Center is the RSMC for this basin and monitors the storms that develop or move into the defined area of responsibility.