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Tropical Cyclone Climatology



Climatology | Names | Wind Scale | Extremes | Models | Breakpoints
Contents


Overview

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 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.


Tropical Cyclone formation regions with mean tracks (courtesy of the NWS JetStream Online School)

 

Atlantic and Eastern Pacific Hurricane Season Normal Activity

The Atlantic hurricane season runs from June 1 to November 30. The Atlantic basin includes the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Based on a 30-year climate period from 1991 to 2020, an average Atlantic hurricane season has 14 named storms, 7 hurricanes, and 3 major hurricanes (Category 3, 4, or 5 on the Saffir-Simpson Hurricane Wind Scale). The first named storm typically forms in mid to late June, the first hurricane tends to form in early to mid-August, and the first major hurricane forms in late August or early September.

The eastern Pacific hurricane season runs from May 15 to November 30. The eastern Pacific basin extends from Mexico and Central America westward to 140°W. Based on a 30-year climate period from 1991 to 2020, an average eastern Pacific hurricane season has 15 named storms, 8 hurricanes, and 4 major hurricanes. The first named storm typically forms in early to mid-June, the first hurricane tends to form in late June, and the first major hurricane forms in mid-July.

The following tables describe the progress of typical hurricane seasons in the Atlantic and eastern Pacific basins by showing benchmark dates when a given number of named storms, hurricanes, and major hurricanes typically forms. It is important to note, however, that formation dates in individual hurricane seasons could vary considerably from these average dates.



Table 1. Progress of the average Atlantic season (1991-2020). Date upon which the following number of events would normally have occurred.
Number Named systems Hurricanes Major Hurricanes
1Jun 20 Aug 11Sep 1
2Jul 17 Aug 26Sep 19
3Aug 3 Sep 7 Oct 28
4Aug 15 Sep 16-
5Aug 22 Sep 28-
6Aug 29 Oct 15-
7Sep 3 Nov 15-
8Sep 9 --
9Sep 16 --
10Sep 22--
11Oct 2 --
12Oct 11--
13Oct 25--
14Nov 19--

Table 2. Progress of the average eastern Pacific season (1991-2020). Date upon which the following number of events would normally have occurred.
Number Named systems Hurricanes Major Hurricanes
1 Jun 10Jun 26Jul 15
2 Jun 24Jul 15Aug 15
3 Jul 6 Jul 31Sep 13
4 Jul 15Aug 16Oct 22
5 Jul 23Aug 31-
6 Aug 3 Sep 15-
7 Aug 11Sep 28-
8 Aug 21Oct 23-
9 Aug 28--
10Sep 4 --
11Sep 14--
12Sep 21--
13Oct 2 --
14Oct 15--
15Nov 5 --


Seasonal Tropical Cyclone Activity

Atlantic Peak Of Season

Pacific Peak Of Season

These charts show the amount of tropical cyclone activity, in terms of named storms and hurricanes, that occurs in the Atlantic and east Pacific basins on each calendar day between May 1 and December 31. Specifically, they show the number of hurricanes (yellow area), and combined named storms and hurricanes (red area) that occur on each calendar day over a 100-year period. The data have been smoothed using a 5-day running average centered on each calendar day. For the Atlantic basin (the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico), the chart is based on data from the 77-year period from 1944 to 2020 (starting at the beginning of the aircraft reconnaissance era) but normalized to 100 years. The official hurricane season for the Atlantic basin is from June 1 to November 30, but tropical cyclone activity sometimes occurs before and after these dates, respectively. The peak of the Atlantic hurricane season is September 10, with most activity occurring between mid-August and mid-October. For the eastern Pacific basin, the analyses are based on data from the 50-year period from 1971 to 2020 (starting when there was reliable satellite imagery) but also normalized to 100 years. The official hurricane season for the eastern Pacific basin is from May 15 to November 30, but tropical cyclones occasionally occur before and after these dates, respectively. A peak in activity is noted in late August, but this peak is less pronounced than the peak in Atlantic activity. Relatively high levels of activity in the eastern Pacific tend to be spread out over a longer portion of the season than in the Atlantic, with most tropical cyclones occurring between late June and early October.


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.

 May 1-10 Tropical Cyclone Genesis Climatology

 May 11-20 Tropical Cyclone Genesis Climatology

 May 21-31 Tropical Cyclone Genesis Climatology

 June 1-10 Tropical Cyclone Genesis Climatology

 June 11-20 Tropical Cyclone Genesis Climatology

 June 21-30 Tropical Cyclone Genesis Climatology

 July 1-10 Tropical Cyclone Genesis Climatology

 July 11-20 Tropical Cyclone Genesis Climatology

 July 21-31 Tropical Cyclone Genesis Climatology

 August 1-10 Tropical Cyclone Genesis Climatology

 August 11-20 Tropical Cyclone Genesis Climatology

 August 21-31 Tropical Cyclone Genesis Climatology

 September 1-10 Tropical Cyclone Genesis Climatology

 September 11-20 Tropical Cyclone Genesis Climatology

 September 21-30 Tropical Cyclone Genesis Climatology

 October 1-10 Tropical Cyclone Genesis Climatology

 October 11-20 Tropical Cyclone Genesis Climatology

 October 21-31 Tropical Cyclone Genesis Climatology

 November 1-10 Tropical Cyclone Genesis Climatology

 November 11-20 Tropical Cyclone Genesis Climatology

 November 21-30 Tropical Cyclone Genesis Climatology


Typical Tropical Cyclone Occurrence Areas by Month

These maps show where tropical cyclones (named storms and hurricanes) tend to occur during each month of the hurricane season. The data are shown as the number of named storms or hurricanes whose centers pass within 150 nautical miles of a point on the map during a 100-year period. For the Atlantic basin, the analyses are based on data from the 77-year period from 1944 to 2020 (starting at the beginning of the aircraft reconnaissance era) but normalized to 100 years. For the eastern and central Pacific basins, the analyses are based on data from the 50-year period from 1971 to 2020 (starting when there was reliable satellite imagery) but also normalized to 100 years. Please note that the map legends vary from basin to basin and between named storms and hurricanes (but not between months) in order to make climatological patterns more apparent.


Atlantic Named Storms

Atlantic Hurricanes

June TC Climatology

June Hurricane Climatology

July TC Climatology

July Hurricane Climatology

August TC Climatology

August Hurricane Climatology

September TC Climatology

September Hurricane Climatology

October TC Climatology

October Hurricane Climatology

November TC Climatology

November Hurricane Climatology





Eastern and Central Pacific Named Storms

Eastern and Central Pacific Hurricanes

June TC Climatology

June Hurricane Climatology

July TC Climatology

July Hurricane Climatology

August TC Climatology

August Hurricane Climatology

September TC Climatology

September Hurricane Climatology

October TC Climatology

October Hurricane Climatology

November TC Climatology

November Hurricane Climatology





Central Pacific Named Storms

Central Pacific Hurricanes

June TC Climatology

June Hurricane Climatology

July TC Climatology

July Hurricane Climatology

August TC Climatology

August Hurricane Climatology

September TC Climatology

September Hurricane Climatology

October TC Climatology

October Hurricane Climatology

November TC Climatology

November Hurricane Climatology



High Resolution History Maps


[Tropical Cyclone History Map for Atlantic and Eastern Pacific]
All North Atlantic and Eastern North Pacific tropical cyclones


Named Cyclones by Year


[Graph of Tropical Cyclone Activity in the Atlantic Basin]
Bars depict number of named systems (yellow), hurricanes (red), and category 3 or greater (purple), 1850-2014
Download hires image
Download table of data (PDF)


Hurricane Return Periods

Hurricane return periods are the frequency at which a certain intensity of hurricane can be expected within a given distance of a given location (for the below images 50 nm or 58 statute miles). In simpler terms, a return period of 20 years for a major hurricane means that on average during the previous 100 years, a Category 3 or greater hurricane passed within 50 nm (58 miles) of that location about five times. We would then expect, on average, an additional five Category 3 or greater hurricanes within that radius over the next 100 years.

More information on return periods can be found from NOAA Technical Memorandum NWS NHC 38 (pdf) on the NHC Risk Analysis Program (HURISK).

Note: The information on return period is generated with the 1987 HURISK program, but uses data through 2010.

 

[Map of return period in years for hurricanes passing within 50 nautical miles]
Estimated return period in years for hurricanes passing
within 50 nautical miles of various locations on the U.S. Coast


[Map of return period in years for major hurricanes passing within 50 nautical miles]
Estimated return period in years for major hurricanes passing
within 50 nautical miles of various locations on the U.S. Coast


CONUS Hurricane Strikes


[Map of 1950-2017 CONUS Hurricane Strikes]
1950-2017 CONUS Hurricane Strikes (Courtesy of NCEI)


CONUS Hurricane Strike Density (county maps)


[Map of 1900-2010 Hurricane Strikes by U.S. counties/parishes]
1900-2010 U.S. Hurricane Strikes


[Map of 1900-2010 Hurricane Strikes by U.S. counties/parishes (West Gulf)]
1900-2010 U.S. Hurricane Strikes - West Gulf


[Map of 1900-2010 Hurricane Strikes by U.S. counties/parishes (East Gulf)]
1900-2010 U.S. Hurricane Strikes - East Gulf


[Map of 1900-2010 Hurricane Strikes by U.S. counties/parishes (Southeast)]
1900-2010 U.S. Hurricane Strikes - Southeast


[Map of 1900-2010 Hurricane Strikes by U.S. counties/parishes (Northeast)]
1900-2010 U.S. Hurricane Strikes - Northeast


[Map of 1900-2010 Major Hurricane Strikes by U.S. counties/parishes]
1900-2010 U.S. Major Hurricane Strikes


[Map of 1900-2010 Major Hurricane Strikes by U.S. counties/parishes (West Gulf)]
1900-2010 U.S. Major Hurricane Strikes - West Gulf


[Map of 1900-2010 Major Hurricane Strikes by U.S. counties/parishes (East Gulf)]
1900-2010 U.S. Major Hurricane Strikes - East Gulf


[Map of 1900-2010 Major Hurricane Strikes by U.S. counties/parishes (Southeast)]
1900-2010 U.S. Major Hurricane Strikes - Southeast


[Map of 1900-2010 Major Hurricane Strikes by U.S. counties/parishes (Northeast)]
1900-2010 U.S. Major Hurricane Strikes - Northeast


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)

  Hurricanes Tropical Storms Tropical Depressions Total
Total Number 58 46 59 163
Percent of All Systems 36% 28% 36%  

Tropical Cyclones in the Central Pacific By Year

Central Pacific Tropical Cyclones per year from 1971 to 2013

Tropical Cyclones in the Central Pacific By Month

Central Pacific Tropical Cyclones per month from 1971 to 2013

The following charts show the storms that have come within 200 miles and 75 miles of Hawaii. Storms that do not make landfall in Hawaii can still cause considerable damage, mostly from winds and surf.

Tropical Storms and Hurricanes Passing within 200 Miles of Hawaii since 1950

Tropical Storms and Hurricanes Passing within 75 Miles of Hawaii since 1950


Learn more about climate impacts from the NWS Climate Prediction Center.