25 May 2022

Hurricane season officially begins in one week, but will it start early AGAIN?

The official Atlantic hurricane seasons spans June 1 through November 30, but nature is of course not bound to those arbitrary dates.  In fact, there have been "pre-season" named storms every year since 2015 -- this would be the eighth consecutive year if it should occur!
So, what are the chances of something developing before June 1? Pretty slim, but it could be close.  Models have been persistently showing the possibility of development in the southern Gulf of Mexico in 7-10 days.  In this latest European model ensemble plot (below), the probability of a tropical cyclone existing before June 1 is shown on the top and before June 3 on the bottom.  From this, the chances appear to be minimal before the official start of the season, but then jump up in the days that follow.  And this is for any tropical cyclone -- if we raise the bar to tropical storm intensity (a named storm), the peak values in the Gulf are in the 10-20% range.  

In short, this is nothing to be concerned about, but something to at least keep an eye on as we head into the first week of the season, and especially if you're in any of the areas surrounding the Gulf of Mexico.

The seasonal forecasts of overall activity indicate that yet another above-average season is likely.  There are a few large-scale environmental signals that go into that outlook, but a notable player is the persistent La Niña.  La Niña is defined to exist when the water temperatures in the equatorial eastern Pacific Ocean are significantly cooler than average, and one of the teleconnections that has is to reduce the vertical wind shear across the tropical Atlantic, making hurricanes more likely to develop and intensify (all other things being equal).

But what makes this expectation of another active season remarkable is that it would be the seventh consecutive above-average season!  If we look at ACE (Accumulated Cyclone Energy), the past six seasons all had values of 132+.  The average over the past fifty years is 104.  But, never in recorded history were there more than three consecutive seasons with 130+ ACE, let alone six or seven.  This is an unprecedented prolonged span of elevated activity.

The name list this season begins with Alex, Bonnie, and Colin, and new names on it are Martin and Owen.  There are six lists of names that are used cyclically, unless a name gets retired due to a particularly devastating impact somewhere.

This list first appeared in 1980, and 9 of the 21 original names have been replaced at some point in the past 42 years.  This table shows the evolution of the list, with retired storm names in red bold font, replacement names in blue italics, and the single occurrence of a retired replacement name (Igor in 2010) in purple bold italics. Unused names that season are indicated by gray font.  Time well tell how far down the list 2022 will go!

Finally, if you missed my post in early April on the Cone of Uncertainty Update and Refresher, please check that out too.

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