This analysis counts hurricanes with rapid intensification defined by an increase of >= 30 knots in 24 hours. It also counts more extreme categories which are inclusive (storms with >= 40 knots are also >= 30 knots) Then divides the number of RI hurricanes in each category by the total number of hurricanes for the year.

In general >=30 knot RI is common, the majority of hurricanes have at least one 24 hour period of RI. Variations in more extreme RI appear to come in recent multi-year clusters, e.g. 2005-2010 and again 2015-17. The more common >= 30 knots, is probably not very meaningful anymore.

Another plot below includes all tropical storms in the denominator and tropical storms with RI in the numerator. The drop in the lowest category RI is almost undoubtedly due to more TS being detected and named. I think the reason for the downward trend in RI versus TS is the detection of large numbers of weak storms using the scatterometer. Those are marginal to begin with and have a lower chance of RI.

Another plot below shows the trend of rapid weakening of storms that are not over land. That's obviously a crucial distinction since storms always weaken over land, often rapidly. Storms with the highest rates of weakening are included in the rapid intensification table. Some storms rapidly weakened in high latitudes which is expected and should show no trend. However, others like Beulah (1967) "unexpectedly collapse" in low latitudes, or are weakened rapidly by a dry air mass like Allen (1980) or proximity to land like Mitch (1998). It's possible that the slowing of hurricanes leads to more weakening. It's also possible that due to the increase in the strongest storms there are more opportunities for rapid weakening.

The final plot below shows RI for the period 1982 to 2009. According to an article in the Washington Post, A 2019 study in the journal Nature ( https://www.nature.com/articles/s41467-019-08471-z) documented a trend toward more rapidly intensifying hurricanes in the Atlantic Ocean between 1982 and 2009, and used a model that determined it would have been unlikely without human-caused climate change. There is a slight increase in RI in that interval due to the start and end points. However the paper uses an RI ratio which is the number of RI periods (24 hours) divided by the total number of 24h periods.

The problem with the ratio seems to be that the numerator is often zero (shown in their fig 3b to the left) due to too few hurricanes in that year. The zeroes makes the trend sensitive to the start and end points, unlike the blue points in the charts below. The red and black points are sensitive to starting and ending points. The upward trends since 1950 may be the most valid. Put another way, it appears that storms with 70 knot RI have become much less rare as shown in the table below. Also the RI ratio (calculated similarly to the nature paper) has more data to work with, and a slope of 3.9e-04 versus 2.4e-03 in the 1982-2009 interval. Note: to match the nature plots (more or less) I had to use > 30 knots instead of >= 30 knots for the a 24 hour RI threshold. The caption for fig 3b indicates that they using "above 30 knots" i.e. >= 35 knots.


We can cut the slope to 3.7e-04 by going back to 1920, although with the caveat that the pre-satellite data has a considerable number of missing observations and completely missed storms which may increase the weight of RI storms.


Here's a list of RI storms since 1950. Some of the more recent storm numbers have been validated from other sources. Peak wind column is from the list of strongest Atlantic storms https://en.wikipedia.org/wiki/List_of_Atlantic_hurricane_records#Strongest_by_1-minute_sustained_wind_speed. Preceding the table below are Labor Day (1932) and Cuba (1935) hurricanes. Undoubtedly there are other strong storms in pre-satellite, pre-hurricane hunter eras that would have be included if their peak winds happened to be measured.

(Note: all numbers are in knots)

Year	Name	24h inc	36h inc	6h inc	peak wind	24h decr
1950	BAKER	30	35	10
	DOG	35	35	10		-35
	ITEM	30	40	10
	KING	50	50	20
1951	ABLE	35	40	10
	CHARLIE	35	45	15
	EASY	30	40	10		-30
	HOW	30	40	10
1952	CHARLIE	35	55	10
	EASY	40	50	10
	FOX	55	60	20
1953	CAROL	40	60	10
	EDNA	30	35	10
	FLORENCE	45	50	15
	HAZEL	30	40	10
1954	ALICE	45	45	15
	CAROL	35	40	10
	DOLLY	35	35	10
	HAZEL	30	30	10
	ALICE	30	35	10
1955	CONNIE	35	40	10
	DIANE	30	30	10
	FLORA	30	30	10
	GLADYS	35	40	15
	IONE	40	45	15
	HILDA	50	55	15
	JANET	40	60	10	150
	KATIE	40	50	10
1956	ANNA	45	45	15
	BETSY	30	40	10		-30
	FLOSSY	30	40	10
1957	AUDREY	35	45	10
	FRIEDA	30	30	10
1958	CLEO	45	55	15
	DAISY	30	50	15
	ELLA	35	55	15
	FIFI	35	45	10
	HELENE	45	55	15
	ILSA	30	40	10		-30
1959	1959169N26274	35	40	10
	DEBRA	35	45	15
	GRACIE	35	45	15
	HANNAH	30	40	15
	JUDITH	30	30	10
1960	CLEO	40	50	5
	DONNA	30	45	10
	ETHEL	60	70	20		-30
1961	BETSY	35	40	10
	CARLA	30	35	10
	DEBBIE	35	40	15
	ESTHER	40	45	15		-30
	FRANCES	40	45	15		-35
	HATTIE	45	65	15
1962	ALMA	30	40	10
1963	ARLENE	40	45	10		-35
	BEULAH	30	45	10		-30
	1963253N26293	30	35	5
	EDITH	50	60	20
	FLORA	45	60	20
1964	1964210N19314	30	40	10
	CLEO	45	65	15
	GLADYS	40	50	20
	HILDA	45	60	20
	ISBELL	40	55	15
1965	ANNA	40	55	10
	BETSY	50	55	20
	CAROL	30	40	10
	ELENA	30	40	10
1966	ALMA	50	55	30		-30
	BECKY	40	40	30
	CELIA	40	45	10
	FAITH	35	45	20
	INEZ	35	50	15		-50
1967	CHLOE	35	45	10
	BEULAH	45	60	15		-55
	DORIA	30	40	25
	FERN	45	45	15
1968	ABBY	35	35	5
	DOLLY	35	35	15
1969	BLANCHE	45	45	40
	CAMILLE	60	85	25	150
	DEBBIE	35	45	20
	FRANCELIA	35	45	15
	GERDA	65	80	25
	HOLLY	45	45	15
	INGA	30	40	10
	MARTHA	35	35	10
1970	ALMA	45	45	30
	CELIA	70	75	40
	ELLA	45	55	20
1971	1971216N31297	45	55	15
	BETH	40	45	15
	FERN	35	50	15
	EDITH	65	75	20
1972	BETTY	30	35	20
1973	ALICE	35	40	10
	BRENDA	35	35	20
	FRAN	35	35	10
1974	BECKY	45	55	15
	CARMEN	45	65	20
	FIFI:ORLENE	40	55	15
	GERTRUDE	35	35	20
1975	BLANCHE	35	40	5
	CAROLINE	35	60	30
	ELOISE	40	50	10
	FAYE	35	50	10
	GLADYS	40	40	10		-35
1976	BELLE	45	60	15
	CANDICE	30	30	25
	FRANCES	35	35	15		-30
	HOLLY	40	40	20
1977	ANITA	65	70	30	150
	CLARA	35	35	20
	EVELYN	35	40	15
1978	CORA	55	55	15
	ELLA	50	60	20		-55
	GRETA	30	40	15
	KENDRA	35	35	10
1979	BOB	35	45	10
	DAVID	60	80	20	150
	FREDERIC	30	40	10
	GLORIA	35	40	10
	HENRI	40	45	10
1980	ALLEN	45	60	15	165	-55
	BONNIE	40	40	20
	GEORGES	30	40	15
	FRANCES	35	45	10
	IVAN	30	35	10
	JEANNE	30	35	10
1981	FLOYD	35	50	10
	GERT	40	50	10
	HARVEY	45	55	30		-35
	IRENE	30	40	10
	KATRINA	35	45	10
1982	ALBERTO	50	50	25
	DEBBY	40	60	15		-40
1983	ALICIA	30	40	15
	BARRY	30	40	5
	CHANTAL	35	40	10
1984	DIANA	40	50	15		-30
1985	DANNY	35	45	10
	ELENA	35	45	10
	GLORIA	35	55	20		-45
	KATE	35	40	15
1986	EARL	40	50	15
	FRANCES	35	45	10
1987	EMILY	60	70	25
1988	DEBBY	35	40	15
	GILBERT	50	55	20	160
	HELENE	30	45	10
	JOAN:MIRIAM	45	55	15		-40
1989	CHANTAL	35	45	10
	FELIX	30	35	10
	GABRIELLE	30	40	10
	HUGO	50	60	15
1990	BERTHA	30	35	10
	DIANA	35	40	10
	ISIDORE	30	40	10
	NANA	30	40	10
1991	BOB	30	40	10
	CLAUDETTE	55	70	20		-30
1992	ANDREW	65	90	20	150
	BONNIE	45	55	20
	CHARLEY	30	50	10
1993	GERT	40	50	15
	HARVEY	35	35	15
1994	FLORENCE	35	35	15
1995	ALLISON	30	35	5
	ERIN	30	30	10
	FELIX	40	50	10
	HUMBERTO	30	40	5
	IRIS	40	40	20
	LUIS	45	65	20
	MARILYN	30	40	5
	OPAL	50	60	20
	ROXANNE	45	55	15
1996	BERTHA	30	35	20
	EDOUARD	50	60	20		-30
	HORTENSE	30	45	15		-30
	ISIDORE	35	40	10
	MARCO	30	35	5
1997	DANNY	35	40	10
	ERIKA	30	35	15
1998	BONNIE	30	40	10
	DANIELLE	40	55	15
	EARL	35	45	20
	GEORGES	40	45	15		-35
	JEANNE	30	40	10
	MITCH	45	60	15	155	-55
1999	CINDY	35	45	15		-30
	BRET	55	70	30
	FLOYD	40	50	15		-30
	GERT	30	40	10
	IRENE	30	30	15
	LENNY	50	60	20		-50
2000	ALBERTO	30	40	10		-40
	DEBBY	35	45	10
	FLORENCE	35	35	20
	ISAAC	55	60	20		-30
	JOYCE	30	40	10
	KEITH	65	80	25		-45
	MICHAEL	30	30	10
2001	ERIN	50	65	15
	FELIX	35	50	10
	HUMBERTO	30	50	15
	IRIS	45	50	30
	MICHELLE	45	60	15
2002	GUSTAV	30	35	15
	ISIDORE	40	45	15
	LILI	35	45	15		-30
2003	FABIAN	45	60	15
	ISABEL	45	55	15
2004	ALEX	35	50	15		-40
	CHARLEY	35	50	30
	DANIELLE	35	45	10
	FRANCES	35	55	15
	IVAN	55	65	25
	JEANNE	30	35	15
	KARL	40	50	15		-35
2005	CINDY	35	40	5
	DENNIS	50	65	20
	EMILY	45	60	25
	KATRINA	50	55	25	150	-35
	RITA	60	85	25	155	-40
	STAN	30	40	10
	WILMA	95	105	55	160	-30
	BETA	30	50	15
2006	FLORENCE	30	30	10
	GORDON	40	55	15
	HELENE	30	40	10
2007	DEAN	65	65	20	150
	FELIX	85	100	35	150	-35
	HUMBERTO	55	55	25
	KAREN	30	35	15
	LORENZO	40	40	10
2008	BERTHA	55	60	20		-40
	DOLLY	30	40	15
	GUSTAV	60	70	25
	HANNA	30	35	10
	IKE	70	70	30
	OMAR	45	55	20		-45
	PALOMA	50	60	20
2009	FRED	50	70	20
	IDA	45	55	10
2010	DANIELLE	30	45	15
	EARL	40	60	10		-40
	IGOR	65	70	25
	JULIA	50	75	20		-35
	KARL	55	70	15
	LISA	40	40	15
	PAULA	35	55	15
	TOMAS	35	50	15
	SHARY	30	35	10
2011	KATIA	30	35	10		-35
	OPHELIA	40	50	15		-50
	RINA	50	60	15		-35
2012	CHRIS	30	35	10
	GORDON	35	40	15
	KIRK	35	45	10
	MICHAEL	50	55	15
	SANDY	40	55	15		-30
2013	BARBARA	30	30	10
2014	BERTHA	30	30	10
	GONZALO	35	50	15
2015	DANNY	45	55	15		-40
	FRED	35	45	10
	JOAQUIN	45	55	20		-45
2016	ALEX	30	30	10
	GASTON	35	45	10
	MATTHEW	75	85	25		-30
	NICOLE	40	55	15		-45
	OTTO	40	40	15
2017	FRANKLIN	35	35	10
	HARVEY	40	55	10
	IRMA	45	60	15	155
	JOSE	40	60	15		-30
	KATIA	40	45	20
	LEE	35	45	15
	MARIA	70	85	35	150
	NATE	40	45	15
2018	BERYL	35	40	15
	CHRIS	30	40	15
	FLORENCE	50	60	15		-40
	MICHAEL	35	50	10
	OSCAR	30	35	10
2019	DORIAN	35	45	15	160	-40
	JERRY	35	45	10
	LORENZO	40	50	15		-40
2020	HANNA	30	40	10
	GENEVIEVE	50	70	25		-35
	LAURA	55	65	20
	TEDDY	35	40	20
	SALLY	30	35	20
	DELTA	65	90	20
	EPSILON	45	55	15
	ZETA	35	40	15
	ETA	70	90	25

* 2020 data from IBTRACS is provisional, containing a Pacific storm and missing some Atlantic storms

Code: hurricanes.py | elevations.py | Data: hurdat.csv | Instructions: README