Thursday, June 27th, 2019
Excerpts from https://www.nhc.noaa.gov/climo/
A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has a closed low-level circulation. Tropical cyclones rotate counterclockwise in the Northern Hemisphere. They are classified as follows:
- Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less.
- Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots).
- Hurricane: A tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher. In the western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
- Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale.
Tropical cyclones forming between 5 and 30 degrees North latitude typically move toward the west. Sometimes the winds in the middle and upper levels of the atmosphere change and steer the cyclone toward the north and northwest. When tropical cyclones reach latitudes near 30 degrees North, they often move northeast.
Atlantic & Eastern Pacific Climatology
The Atlantic hurricane season runs from June 1st to November 30th, and the Eastern Pacific hurricane season runs from May 15th to November 30th. The Atlantic basin includes the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. The Eastern Pacific basin extends to 140°W.
The following figures and tables describe the progress of a typical hurricane season in terms of the total number of tropical systems and hurricanes produced throughout the year in the Atlantic and East Pacific basins.
In the figures, curves represent the average cumulative production of all named tropical systems, all hurricanes, and those hurricanes which were Category 3 or stronger in those basins.
For example, by the beginning of September in an average year we would expect to have had four named systems, two of which would be hurricanes and one of which would be of category 3 or greater in strength.
The tables list benchmark dates when a given number of tropical systems, hurricanes, or category 3 storms should have been generated.
The official hurricane season for the Atlantic Basin (the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico) is from 1 June to 30 November. As seen in the graph above, the peak of the season is from mid-August to late October. However, deadly hurricanes can occur anytime in the hurricane season.
Points of Origin by 10-Day Period
The figures below show the points of tropical cyclone genesis by 10-day periods during the hurricane season. These figures depict named storms only. The source years include 1851-2015 for the Atlantic and 1949-2015 for the Eastern Pacific from the HURDAT database.
Climatological Areas of Origin and Typical Hurricane Tracks by Month
The figures below show the zones of origin and tracks for different months during the hurricane season. These figures only depict average conditions. Hurricanes can originate in different locations and travel much different paths from the average. Nonetheless, having a sense of the general pattern can give you a better picture of the average hurricane season for your area.
Central Pacific Climatology
The following graphs and charts describe some of the climatology of tropical cyclone activity in the area served by the Central Pacific Hurricane Center, between 140 degrees West longitude and the International Date Line and north of the equator.
Many factors affect the level of tropical cyclone activity from year to year. Among them are the state of the El Nino Southern Oscillation in the Pacific. Moderate to strong El Nino years are correlated with increased tropical cyclone activity in the Central Pacific and the occurrence of late season storms.
Continuous satellite coverage has been available in the Central Pacific since 1971 so many climatologies start with that date.Earlier accounts of tropical cyclone activity are based on land, ship, and aircraft observations as well as some non-continuous satellite data. Hurricane Season Climatology Central Pacific (1971-2008)