Tropics extremely quiet in Atlantic; record drought in major U.S. hurricane landfalls

October 15, 2013

The tropical Atlantic continues its spell of remarkable inactivity.  There have been just two short-lived Category 1 hurricanes so far, and there is nothing in the long-range model guidance to suggest anything but the status quo.


Enhanced water vapor image from early this morning of the tropical Atlantic showing big pockets of dry air and strong wind shear. (NASA)

And this suppressed activity isn’t limited to just the Atlantic either.  The East Pacific has now had 14 tropical storms, but like the Atlantic, no major hurricanes.  This is extraordinary, since the two basins are typically out of phase; that is, one is active while the other is inactive.  The only other year in recorded history in which no major hurricanes occurred in the Atlantic or the East Pacific is 1968.

“Best track” data extend back to 1949 in the East Pacific and to 1851 in the Atlantic, so only the past 64 years are shared in common.  However, reliable intensity data in the East Pacific begins in 1971, so in that era, the absence of major hurricanes in both basins is unprecedented.


Number of known major hurricanes in the East Pacific (red) and Atlantic (blue) going back to 1949. A yellow marker highlights 1968, the only year with zero in both basins.

Expanding the search even further, it turns out that the West Pacific is also abnormally quiet this year, even accounting for last week’s flurry of storms.  In terms of ACE (Accumulated Cyclone Energy), the entire northern hemisphere is running behind climatology.

Ryan Maue at WeatherBell keeps track of ACE, basin-by-basin.  The northern hemisphere as a whole is at about 59% of average for this date.  The East Pacific is at 45% and the Atlantic is at 30%.  Only the typically-quiet Indian Ocean is now above normal due almost entirely to last week’s Cyclone Phailin.

Going back to 1950, Atlantic ACE is the 7th lowest for this date, so while it’s low, it’s definitely not a record.  Not that it is a race, but, to just “catch up” to climatology for this date, we’d need to toss in a little more than three Hurricane Katrinas!  And, to reach 2004′s record ACE for this date, we’d need to add about ten Hurricane Katrinas!


Cumulative ACE values for all Atlantic hurricane seasons since 1950. The average is shown in black, and 2013 is shown in red.

Record-long U.S. major hurricane landfall drought

As a result of having no major hurricanes yet this year, the U.S. “major hurricane drought” necessarily continues.

It has now been 2,913 days since the last major hurricane made landfall on the U.S. … the longest such span going back to 1900.  A major hurricane is defined to be a hurricane with maximum sustained winds of 115 mph or greater… Category 3, 4, and 5 on the Saffir-Simpson scale.


Going back to 1900, this graph shows the number of days between consecutive major hurricane landfalls on the U.S. This helps to put the current span in perspective. (Adapted from http://rogerpielkejr.blogspot.com)

The last one was Wilma, which made landfall on southwest Florida on October 24, 2005 with peak winds of about 120 mph.  We’ve had several weaker hurricanes make U.S. landfall since then (Humberto ’07, Dolly ’08, Gustav ’08, Ike ’08, Irene ’11, Isaac ’12, and Sandy ’12), but nothing with the violent fury of a major hurricane.

Also, there have been quite a few major hurricane landfalls on other countries since 2005; we’ve just been lucky here in the States.  Of course, as we know from experience, even weaker storms are capable of generating destructive storm surges and flash floods.

No one’s complaining about this, but there is one downside: complacency.  Anywhere you live, there are verbal accounts of past major storms that live on in people’s memories.  But the longer you go without a significant event, the harder it becomes to convince people to take action when one finally threatens.  It is a 100% certainty that it will happen again, but there will be lots of people who won’t know what they’re in for if they choose to ride it out.

There is already research underway by several universities to figure out what is suppressing tropical cyclone activity not just in the Atlantic, but across the northern hemisphere this year.  It’s nothing routinely obvious, because expert forecasters were all expecting a very active season (see “What happened to hurricane season? And why we should keep forecasting it…“), but it must be some fundamental large-scale phenomenon that has been overlooked.

I often get asked what role global warming is playing in a given hurricane season… whether it’s an abnormally quiet one or an abnormally active one.  It is never accurate to correlate a hurricane season –and certainly not a specific hurricane– with global warming. Regardless of where you stand in the debate, natural inter-seasonal variability is so large that subtle signals due to climate change are overwhelmed.  That is not to say that trends might not show up in long-term averages and climatology, but one should not cherry-pick individual seasons and storms to make a case in the debate.

Finally, keep in mind that hurricane season is not over yet, and even a single hurricane making landfall in a vulnerable location can make it a very expensive and destructive season… but it won’t be enough to make it an active season.

Related: What happened to hurricane season? And why we should keep forecasting it…

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Jason Samenow · October 15, 2013