An earlier version of this story was published in 2017.

Isabel. Ivan. Ike. Irene. Irma. And now Ida. These terrible hurricanes, all of which have occurred since 2003, begin with a common vowel. They haven’t all started with the same letter by chance — there is some science behind the abundance of notorious storms starting with the letter “I.”

Since 1953, storms have been given human names to make identifying them more convenient. For 26 years they were given only female names, but in 1979 the male-female alternating alphabetical lists that we use today were introduced.

Names associated with storms that cause severe loss of life or property damage are retired by the World Meteorological Organization. The idea of permanently retiring a storm name began after the 1954 hurricane season when Carol, Edna and Hazel ravaged the East Coast.

Since that fateful year, a total of 94 storm names have been retired, and the count of those beginning with “I” totals more than any other letter: 11.

Here they all are, listed by year: Ione ’55, Inez ’66, Iris ’01, Isidore ’02, Isabel ’03, Ivan ’04, Ike ’08, Igor ’10, Irene ’11, Ingrid ’13, Irma ’17.

The abundance of devastating I-named storms is not entirely surprising: They tend to coincide near the typical peak of the hurricane season between mid-August and the end of September. With warm ocean temperatures and the absence of disruptive high-altitude winds, conditions are typically prime for hurricane development just when 'I' is reached on the alphabetical list of storms.

Over the past 50 years, the average “I” or ninth named storm forms on Sept. 23, toward the tail end of peak hurricane season. But during active seasons, which produce some of the most extreme hurricanes, the average date creeps up by about two weeks, coinciding with the most active part of the peak hurricane period.

The earlier I-named storms, forming in August, have tended to occur during the most active hurricane seasons. During the past 50 years, the five years which have seen nine storms by this date have been very busy seasons: 1995, 2005, 2011, 2012 and 2020.

While we remember with horror storms like Ivan and Irma and brace for Ida, terrible “I” storms haven’t just afflicted the United States. Putting the 11 retired “I” storms on a map reveals that they had an effect on many countries.

Jason Samenow contributed to this report.