Tropical Tidbits: Can we have hurricanes form outside of hurricane season?

Weather Blog

Given the record breaking hurricane season the Atlantic basin has seen this year, I thought I’d dive into some more unusual’s in the tropics category.

. . .

Did you know that hurricanes can and DO happen outside of the normal hurricane season? Let’s take a look at our own Atlantic basin for example:

This season runs from June 1st to November 30th by official standards. How do we arrive at that? It’s pretty much based on the climatology of past tropical systems along with having the most ideal climatological conditions for storm formation such as warm ocean waters and ideal shear environments. Sometimes you can get tropical systems to form outside of that time frame, and after all, who are we to say if a hurricane wants to form on December 1st as opposed to November 30th?

Before we discuss those storms, let’s address this question: when an off season tropical system forms after the normal season ends, do we continue with the list of names used, or do we start over for the next season? What if the storm forms during the year after the season is done?

The way tropical systems are named are based on the procedures decided by the World Meteorological Organization. During the normal season, the names given to each tropical system are based on a list that is rotated every 6 years, so every 6 years the same names are used unless they are destructive enough to be retired, and never used again.

There are only 21 names in the first list, and if we get more than 21 storms in a single season, which we’ve already done this year, we begin using the Greek alphabet list. This has only been done twice in Atlantic hurricane history, so it’s very unlikely we’ll go through a complete cycle of the Greek alphabet by the time we get to the end of hurricane season…. but what happens if a storm forms after November 30th? It has happened before, so let’s look at some of those storms:

The most recent off season storm in the Atlantic basin was Tropical Storm Arthur, and was the first storm to form during the 2020 season this past May. Tropical Storm Bertha was the next named storm, and was also ahead of the normal season forming just shortly after on May 27th, 2020.

There are actually several named storms in history that have formed not only just a little outside of the normal season, but right in the middle of our winter!

Hurricane Alex formed on January 12th-15th back in 2016. The storm was a very unusual January hurricane according to the report from the National Hurricane Center. It formed in the northeastern Atlantic Ocean and made landfall in the Azores as a tropical storm. Another unusual, but short lived off season tropical storm was Tropical Storm Olga that formed December 11th-12th, 2007.

Tropical Storm Zeta formed during the off season in 2006, but it was a part of the record breaking 2005 season. It was the 27th and final named storm for the 2005 Atlantic season, and was one of the only 2 tropical cyclones ever to cross over from one calendar year to the next (December 30th, 2005 – January 7th, 2006).

Have off season hurricanes affected western New York?

It’s been a while since it has, but it has happened before.

  • Hurricane Hazel
Image courtesy: weather.gov

All the way back in 1954, this storm was the deadliest and costliest hurricane of the 1954 season where it topped out as a category 4 hurricane at landfall. This storm was unique in that the original storm had weakened to a tropical depression, before merging with an incoming cold front from the west and restrengthening to hurricane status as it made its way through western and central New York. One of the highest recorded wind gusts from the storm seen in the upstate area was around 94 mph.

This storm originally formed in the tropics and tracked through the Carolina’s before ultimately crossing the Great Lakes, where it then merged with a cold front and weakened as it continued to drop large amounts of rain over the Toronto area.

  • Hurricane Agnes
Image courtesy: weather.gov

This storm occurred in late June of 1972, which is NOT during the off season, but it caused some of the most destructive and widespread flooding to occur across the eastern United States, and to our very own Genesee River. Many of you may remember the most notable effects from this storm to be from the flooding rains that caused major flooding to this river; enough to break historical records at the time.

This storm overall brought heavy, flooding rains form the Carolina’s to portions of New York State.

Image courtesy: weather.gov

It surely has been an interesting year in the tropics so far, and now that we know we can still get hurricanes to form outside of hurricane season, it’s possible our unique season so far could break even more records down the road.

~Meteorologist Christine Gregory

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