When you can expect the first Atlantic hurricane of the season

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  • Since the mid-1960s, the first Atlantic hurricane of the season usually arrives in late July.
  • But that first hurricane happened as early as January and as late as September.
  • A number of them became the first hurricane of the season near the United States

Atlantic hurricane season officially began on June 1, but it usually takes a month or more before the first hurricane of the season develops.

For seven straight years through 2021, hurricane season has started early, with at least one named storm before the season officially kicks off on June 1.

Last year, Elsa became the first hurricane of the 2021 season on July 2 near the Windward Islands.

But how typical is it to wait more than two months into the season before the first hurricane develops?

To answer this, we looked at data from the mid-1960s – when full satellite coverage of the Atlantic Basin began – through 2021 to see how variable the date of the first hurricane of the season has been. We also looked at where those early hurricanes formed and whether early or late early hurricanes told us anything useful about the season as a whole.

Usually in July or August

In 40 of the 56 seasons since 1966, the first Atlantic hurricane of the season has formed in July or August.

The number of times the first Atlantic hurricane season formed during each respective month from 1966 to 2021. Note that this is the date the system first became a hurricane, and not the date it became a tropical depression.

(Data: NOAA/NHC; graphic: Infogram)

It’s logic.

Very early in the season, the wind shear that can disrupt or tear apart tropical cyclones is still at least modest. Areas of dust-laden air from the Sahara Desert push westward across the Atlantic, suppressing thunderstorms necessary for tropical development.

From July, tropical waves – the disturbances that often serve as seeds for tropical storms and hurricanes – become more numerous as they migrate off the coast of Africa. Wind shear decreases towards its seasonal minimum, and ocean temperatures are warming up in the summer heat. These are all favorable factors that combine to support not only tropical storms, but also hurricanes.

But there is variability

Now let’s take a closer look at the actual dates of the first hurricane of the season over the past 56 years, plotted in the graph below.

They are plotted in Julian Days – where January 1 would be Julian Day 1, February 1 would be Julian Day 32 and so on. We did this in order to calculate the average day you expect the first hurricane of the season to form, which is July 24th.

Dates of the first Atlantic hurricane of the season from 1966 to 2021, expressed in Julian days, where January 1 is Julian day 1. The first notable outliers in 1970 and 2016 are labeled.

(Data: NOAA/NHC; graphic: Infogram)

But as you can see, there is a lot of variability in this date.

In 1970, Alma briefly became a hurricane on May 20 between Jamaica and Honduras before weakening to a tropical depression 36 hours later in the western Caribbean Sea.

In 2016, Hurricane Alex made a frightening appearance in mid-January south of the Azores in the eastern Atlantic Ocean.

We have also waited a very long time for the first hurricane, including several times this century.

The first hurricane of the 2013 season did not develop until September 11 (Humberto). This was also the case in 2002, with Gustav.

Is the timing of the first hurricane tied to an active season?

Since 1966, we have found 13 seasons in which the first hurricane formed at least three weeks earlier than the July 24 mean date, 21 seasons in which it formed within three weeks of the mean date, and Another 22 seasons in which he trained for at least three weeks. later than average.

As expected, the “early first hurricane” seasons had about one to two more storms and hurricanes than the “early first hurricane” seasons.

However, years with a near-average arrival of the first hurricane have had the most storms and hurricanes.

Total number of storms (yellow bars) and hurricanes (red bars) that occurred in seasons with an early first hurricane (left), a date near the average first hurricane (middle bars), and a first late hurricane (right – most bars) from 1966 to 2021.

(Data: NOAA/NHC; graphic: Infogram)

Since the majority of a season’s activity occurs during its peak from late August through September, whether a storm manages to reach winds of 75 mph in June or early July shouldn’t matter to the weather. whole season. A caveat to this, however, is the tendency for an early hurricane in the so-called primary development region between the Lesser Antilles and West Africa to herald an active season.

However, note that there are about three to four fewer storms and three fewer hurricanes in seasons with a late first hurricane than average.

It is also logical.

While it takes until late August or September to finally generate a hurricane, there may be large-scale conditions — such as persistent wind shear or flowing dry air — over the Atlantic Basin that are more hostile. to tropical development.

Where the first hurricanes started

We have also plotted on the map below the locations of each of the first hurricanes of the season since 1966. As you can see, there is a lot of spray at these points.

Locations where each of the first hurricanes of the season became hurricanes from 1966 to 2021.

(Data: NOAA/NHC)

In general, early season hurricanes tend to form in the western Atlantic, Gulf of Mexico, or Caribbean Sea, which are areas generally favorable for development in June or early July.

Early hurricanes that form later in the season may form over more of the Atlantic Basin.

Perhaps the main takeaway from the map above is how many are becoming the first hurricane of the season relatively close to the United States, particularly in the Gulf of Mexico.

Although not all of them make landfall, especially those off the East Coast, it reminds us that the moment of prepare for hurricane season is now.

The primary journalistic mission of The Weather Company is to report on the latest weather news, the environment and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.



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