How Unusual are 4 Major Atlantic Hurricanes? ‘Not unusual at all’


By: - Climate DepotSeptember 20, 2017 3:12 PM

By Paul Homewood

With Hurricane Maria tearing heading towards Puerto Rico, there will be yet more alarmist claims about how climate change is making hurricanes worse.

Maria is the fourth major hurricane in the Atlantic this year, following Harvey, Irma and Jose. But how unusual is this?

Fortunately we don’t have to rely on Al Gore or Jennifer Lawrence. The reality is that it is not unusual at all.

Leading tropical cyclone expert, Chris Landsea of NOAA’s Hurricane Research Division has put together a list of Atlantic storms back to 1851.

This is what he has to say:

The Atlantic hurricane database (or HURDAT) extends back to 1851. However, because tropical storms and hurricanes spend much of their lifetime over the open ocean – some never hitting land – many systems were “missed” during the late 19th and early 20th Centuries (Vecchi and Knutson 2008). Starting in 1944, systematic aircraft reconnaissance was commenced for monitoring both tropical cyclones and disturbances that had the potential to develop into tropical storms and hurricanes. This did provide much improved monitoring, but still about half of the Atlantic basin was not covered (Sheets 1990). Beginning in 1966, daily satellite imagery became available at the National Hurricane Center, and thus statistics from this time forward are most complete (McAdie et al. 2009).

For hurricanes striking the USA Atlantic and Gulf coasts, one can go back further in time with relatively reliable counts of systems because enough people have lived along coastlines since 1900.

Thus, the following records for the period of reliable data hold for the entire Atlantic basin (from 1966-2016) and for the USA coastline (1900-2016):

 

 

image

& Landsea et al. (2010) documented a rather large increase in short-lived tropical storms and hurricanes in the last decade, which is likely due to improved monitoring capabilities, that may be influencing the climatological average number of TCs in the Atlantic basin. With the artificial jump in the 2000s in the frequency of short-lived systems, a more realistic estimate of the long-term climatology may be closer to 13 tropical storms and hurricanes per year.
* 1950 is recorded as the busiest season in the whole database for number of Major Hurricanes with 8.
+ 1886 is recorded as the most active hurricane season for the continental USA with 7 landfalling hurricanes.

http://www.aoml.noaa.gov/hrd/tcfaq/E11.html

The full list is included in the above link.

It is worth re-emphasising these points:

  • Many storms were missed over the open ocean prior to hurricane hunter aircraft in 1944.
  • Even then half of the Atlantic basin was not covered.
  • Satellite coverage began to improve matters in 1966.
  • But even then monitoring has considerably improved since 1966, particularly regarding short lived storms.

The effect of this improved coverage can be seen in NOAA’s graph of named storms:

NS

 

 

Yet when we look at major hurricanes, we get a totally different picture:

MH

It is still obvious that many storms were, unsurprisingly, not picked up before 1900, and even prior to 1940.

However, since the introduction of hurricane hunters, there has been no increase in the number of major hurricanes. We simply see the dip during the 1970s and 80s, when the AMO was in cold phase.

Contrary to popular myth, the year with most major hurricanes was not 2005, but 1950, when there were eight.

To have four, as we have so far had this year, is not in the slightest unusual. In fact, there have been 27 years on the record, when there has been four or more major hurricanes.

 

 

But are hurricanes getting more powerful?

Well, not according to the ACE index (1), which shows hurricane seasons in the past every bit as strong as the past couple of decades.

The worst year of the lot was 1933.

ACE

(1) ACE measures the Accumulated Cyclone Energy – An index that combines the numbers of systems, how long they existed and how intense they became. It is calculated by squaring the maximum sustained surface wind in the system every six hours that the cyclone is a Named Storm and summing it up for the season. It is expressed in 104 kt2.

 

All graphs and data are from the Hurricane Research Division: