Tropical Cyclone Climatology (Text)

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Tropical Cyclone Climatology (Text)

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.

Figure 1.The average cumulative number of Atlantic systems per year Figure 2.The average cumulative number of Eastern Pacific systems per year

**Table 1.** Progress of the average Atlantic season (1944-2005). Date upon which the following number of events would normally have occurred.
Number	Named systems	Hurricanes	Category 3 or greater
1	July 10	Aug 14	Sep 3
2	Aug 6	Aug 30	Sep 25
3	Aug 20	Sep 9	-
4	Aug 29	Sep 22	-
5	Sep 5	Oct 10	-
6	Sep 12	Nov 17	-
7	Sep 20	-	-
8	Sep 30	-	-
9	Oct 12	-	-
10	Nov 3	-	-

**Table 2.** Progress of the average eastern Pacific season (1966-1996). Date upon which the following number of events would normally have occurred.
Number	Named systems	Hurricanes	Category 3 or greater
1	June 9	June 24	July 19
2	June 23	July 13	Aug 23
3	July 3	July 29	Sep 19
4	July 13	Aug 12	Oct 29
5	July 20	Aug 25	-
6	July 28	Sep 5	-
7	Aug 5	Sep 17	-
8	Aug 14	Oct 2	-
9	Aug 21	Oct 25	-
10	Aug 28	-	-
11	Sep 5	-	-
12	Sep 13	-	-
13	Sep 21	-	-
14	Sep 30	-	-
15	Oct 9	-	-
16	Oct 27	-	-

Number of Tropical Cyclones per 100 Years

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.

(Source: http://hurricanes.noaa.gov/prepare/season.htm)

Tropical Cyclone Return Periods

Hurricane return periods are the frequency at which a certain intensity or category of hurricane can be expected within 75 nm (86 statute miles) of a given location. In simpler terms, a return period of 20 years for a Category 3 or greater hurricane means that on average during the previous 100 years, a Category 3 or greater hurricane passed within 75 nm (86 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.

Our Return Periods webpage has both images and PDF documents that show the average return for Category 1, 2, 3, 4, and 5 hurricanes for selected coastal locations.

This data is produced by the National Hurricane Center Risk Analysis Program (HURISK) by Charles Neumann. The basic idea is that a population of tropical cyclones falling within the 65 nm (75 miles) circle is obtained from the best-track file. For that set of storms, the maximum wind within the circle is found. Then, a count is conducted to find how many systems had winds of 30-34 kt, 35-39 kt etc. Once the count is known, a function is used to "fit" the distribution. Since there are only a few intense tropical cyclones typically in the 100-year record for a particular site, the mathematical function helps to smooth this out and "fill in the holes" so to speak. The smooth function is then used to estimate the number of systems that would occur over a longer time period. We would expect that if we actually had a much longer historical record (several centuries) that the number of extreme events (i.e., category 5 hurricanes) observed would roughly match our estimates based on the shorter period of record.

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.

June Hurricane Climatology

July Hurricane Climatology

August Hurricane Climatology

September Hurricane Climatology

October Hurricane Climatology

November Hurricane Climatology

(Source: http://hurricanes.noaa.gov/prepare/season_zones.htm)

Other Climatology Figures

[Tropical Cyclone History Map for Atlantic and Eastern Pacific]

Figure 1a. All North Atlantic and Eastern North Pacific tropical cyclones
Download high resolution jpg – Download very high resolution pdf (70MB)

[Hurricane History Map for Atlantic and Eastern Pacific]

Figure 1b. All North Atlantic and Eastern North Pacific hurricanes
(at least Category 1 on the Saffir-Simpson Hurricane Scale)
Download high resolution jpg – Download very high resolution pdf (70MB)

[Major Hurricane History Map for Atlantic and Eastern Pacific]

Figure 1c. All North Atlantic and Eastern North Pacific major hurricanes
(at least Category 3 on the Saffir-Simpson Hurricane Scale)
Download high resolution jpg – Download very high resolution pdf (70MB)

[Graph of Tropical Cyclone Activity in the Atlantic Basin]

Figure 2. Bars depict number of named systems (open/yellow),
hurricanes (hatched/green), and category 3 or greater (solid/red), 1886-2004
Download hires image