Warmer Water, SUPER HURRICANES

By: Dr. Jeff Masters , 12:33 PM GMT on July 24, 2007

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The July 2007 issue of Scientific American has an article called "Warmer Oceans, Stronger Hurricanes" (referred to as "Warmer Water, SUPER HURRICANES" on the cover). The article is written by Dr. Kevin E. Trenberth, head of the Climate Analysis Section at the National Center for Atmospheric Research, and a lead author on the landmark 2007 climate report issued by the UN's Intergovernmental Panel on Climate Change (IPCC). The article makes the case that "evidence is mounting that global warming enhances a cyclone's damaging winds and flooding rains." The article presents some solid evidence to substantiate that point of view, which I will share below. However, I was disappointed in the general tone of the piece, which was over-hyped and did not paint an objective view of the current scientific thinking on the global warming/hurricane issue.

The hype
First off, the reader is hit with a dramatic full-page artist's depiction of the global super-hurricane of the future--a massive 5000-mile diameter Caribbean storm the size of North America. The storm's 200-mile eye is wider than the Florida Peninsula! Whoa, I said when looking at the whopper "SciAmicane". No doubt many readers perusing the magazine, trying to decide whether to buy it, had the same reaction and plunked down their $5 to read about this grim threat. OK, lets talk reality here. The largest tropical cyclone on record, Supertyphoon Tip of 1979, had a diameter of 1380 miles--less than one third the size of the SciAmicane. A storm like the SciAmicane cannot physically exist on Earth unless the oceans were to super-heat to about 122°F (50°C). Only an asteroid impact or similar calamity could create such a hypercane. Even the most extreme global warming scenarios do not heat the oceans to 122°, so the SciAmicane is there to sell magazines, not to illustrate what global warming might do to hurricanes.


Figure 1. Comparison of sizes: the Earth, the largest tropical cyclone on record (Supertyphoon Tip of 1979, 1380 miles in diameter), and the recently discovered hurricane-like vortex on Saturn (the Saturnicane). The "SciAmicane" is about the same size as the Saturnicane--5000 miles across.

The article also calls attention to 2004, when "an unprecedented four hurricanes hit Florida, and 10 typhoons made landfall in Japan". I've erroneously made this statement, too, but the truth is that Japan was hit by only four typhoons in 2004. Ten tropical cyclones that were of typhoon strength at some point during their life did hit, yes, but six of these had decayed to tropical storm or tropical depression strength by the time they hit Japan. The article then refers to a "consensus explanation" emerging to explain recent hurricane activity patterns, and "that explanation forebodes meteorological trouble over the long term." I'd say that the issue is still very much under dispute. In fact, the consensus statement on hurricanes and climate change adopted by the World Meteorological Organization in December 2006, in response to the recommendations of a panel of 125 hurricane researchers was thus: "Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point." Trenberth's article gives a list of four publications to read in the "more to explore" section, but none of these include the recent articles that call into question the strength of the global warming/stronger hurricane connection. (I apologize for not reviewing the many excellent articles that have appeared on this subject of late!)

The good science
There's quite a bit of good science in the article, which is worth reading if one keeps in mind its biases. In particular, I like the discussion of how global warming has affected precipitation and atmospheric water vapor. The 0.6°C (1.0°F) rise in Sea Surface Temperatures (SSTs) globally since 1970 has increased water vapor in the atmosphere by 4%, thanks to increased evaporation. This in turn has led to an 8% increase in global precipitation. Trenberth makes the point that no given hurricane can be blamed on global warming, but one can say 8% of a given storm's rainfall is due to global warming. There's also a nice discussion about how weaker than normal trade winds over the tropical Atlantic in 2005 caused less evaporational cooling than normal, allowing the ocean to heat to record temperatures. Finally, the conclusion of the article is one I certainly agree with:

We would all be wise to plan for more extreme hurricane threats.

Both theory and computer models predict a 3-5% increase in hurricane winds per degree C increase in tropical SSTs, and there is concern that the actual increase may be much more than this.

Jeff Masters

For a technical treatment of hypercanes, see Dr. Kerry Emanuel's paper, Hypercanes: a possible link in global extinction scenarios.

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1691. pottery2
8:13 PM AST on July 25, 2007
good evening, everyone,
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1690. eye
12:11 AM GMT on July 26, 2007
jp, you dont see the shear that is going to prevent that blob from developing in the BOC???????
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1688. StormJunkie
12:11 AM GMT on July 26, 2007
Thanks for catching the post SW ☺
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1684. KEEPEROFTHEGATE (Mod)
12:01 AM GMT on July 26, 2007
we got 2 weeks to go then we will see what mid season updates are going to say jp heres my prediction 07 will have 9 storms 6 will be canes 4 will be 5's 2 will be 3's 3 tropical storms
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1683. Tazmanian
5:08 PM PDT on July 25, 2007
is the gulf low to the sfc?
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1682. mermaidlaw
11:52 PM GMT on July 25, 2007
Hello everyone, I hope your night is nice!

PLEASE do not think that the season is over! Be prepared, and stay safe!!
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1679. eye
12:06 AM GMT on July 26, 2007
jp, what will your excuse be coming the end of Aug we we might of had one or two TS....wait until Sept? and when we are in the same boat come middle Sept....wait until next season????
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1678. StormJunkie
12:03 AM GMT on July 26, 2007
eye, there should not even really be many waves coming off right now and the few we saw early in the season are fairly rare. This one looks pretty good considering what time of year it is. Main CV time is late Aug to Late Sept no?
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1675. eye
12:02 AM GMT on July 26, 2007
but these "strong" waves still are going "poof" once they are off a day or so.
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1672. eye
12:01 AM GMT on July 26, 2007
jp, show me a wave that hasnt been choked and/or sheared so far this season.....
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1669. ryang
7:59 PM AST on July 25, 2007
Eye, 2006 had an El Nino, NOT this year.
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1668. StormJunkie
11:57 PM GMT on July 25, 2007
There is not much shear over that way right now eye. And the dust is pretty far N and a good bit weaker also.
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1666. louisianaboy444
11:54 PM GMT on July 25, 2007
you see what is happening here is that ever since the 2005 season these new people compare everything to that season and has forgotten how a typical hurricane season starts...remember guys and i will say this many many times...The 2005 season was like no other it is very rare and very unique they have had several active seasons before 2005 but not everyone has had hurricanes in July like 2005 did...so please you cannot tell how active a hurricane season will be by the first 2 months
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1665. pcshell
7:54 PM EDT on July 25, 2007
hi guys just wanted to pop in and remind the "right off the season" bandwagon that in 2004 my area was hit hard by a storm named charley only the "c" storm and that was not until august 13th the rest of that season proved pretty active if i recall right
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1664. eye
11:54 PM GMT on July 25, 2007
we had strong waves coming off africa last year, that were choked by dust and/or sheared.....this year they are being choked and sheared again....
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1663. KEEPEROFTHEGATE (Mod)
11:49 PM GMT on July 25, 2007
wont be a repeat storms are coming just not as many as forecasted but the ones that do come will be very very strong wait a see usal for this time of year if anything been a decrease in waves they just go poof for some unknown reason
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1662. ryang
7:52 PM AST on July 25, 2007
LOL Pat...
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1661. Patrap
6:51 PM CDT on July 25, 2007
Mo popcorn please..this is good stuff!
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1660. StormJunkie
11:50 PM GMT on July 25, 2007
eye, this year is nothing like last year. This time last year we had not had several strong waves roll off the Africa coast, not to mention there were ULLs everywhere and a giant hole in the high.
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1657. eye
11:42 PM GMT on July 25, 2007
looks like 2007 is gonna be a repeat of 2006

at this time last year was the same old same old(wait until Aug and Sept) When they came there was hardly anything.....biggest thing was Ernesto.......
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1656. ryang
7:46 PM AST on July 25, 2007
I think the NHC has the coordinates to far to the east.
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1655. KEEPEROFTHEGATE (Mod)
11:38 PM GMT on July 25, 2007
can't wait till august then it will be wait till sept wait till oct wait till nov wait till next season lol
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1654. StormJunkie
11:43 PM GMT on July 25, 2007
Guess I should have said canal...lol
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1653. scwindsaloft
11:42 PM GMT on July 25, 2007
Evening SJ...another wonderful day!
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1652. StormJunkie
11:41 PM GMT on July 25, 2007
Well there you have it ryan, not dead...I would expect it will get mentioned in the TWO either tonight or in the morning.
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1651. ryang
7:41 PM AST on July 25, 2007
By the way, A STRONG WAVE, will come of Africa tomorrow, the GFS forecast a TD to form.
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1650. StormJunkie
11:41 PM GMT on July 25, 2007
lol winds, evening ☺ How's life on the river?
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1649. ryang
7:38 PM AST on July 25, 2007
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED JUL 25 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE WILL BE INTRODUCED ALONG 27W S OF 17N MOVING W
ABOUT 15 KT. THERE ARE SEVERAL INDICATIONS OF THIS WAVE. 1...A
WEAK SIGNAL IS NOTED IN THE DAKAR SOUNDING BETWEEN 00Z AND 12Z
ON THE 23RD. 2...A SIGNAL IS NOTED IN THE SAL SOUNDING BETWEEN
12Z ON THE 24TH AND 00Z ON THE 25TH MAINLY IN 850-900 MB LEVEL.
3...A 1946Z QUIKSCAT PASS SHOWS A WEAK CIRCULATION CENTERED W OF
THE CAPE VERDES NEAR 13N27W.
SCATTERED MODERATE CONVECTION IS
FROM 12N-15N BETWEEN 25W-28W.
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1648. scwindsaloft
11:40 PM GMT on July 25, 2007
I third that thought. Let it be done...
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1647. StormJunkie
11:40 PM GMT on July 25, 2007
Evening mlc
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1645. ryang
7:36 PM AST on July 25, 2007
In my opinion, convection should refire tonight, it could have a weak low.
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1644. StormJunkie
11:36 PM GMT on July 25, 2007
I certainly don't think it is dead. The models have been hinting at it for several days, including the Ukmet. I'll be keeping an eye on it. Tonight who knows, but I said yesterday morning that I thought we would see a TD out there with in a week. Just my guess though.
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1643. ryang
7:34 PM AST on July 25, 2007
Well, not that we gave up on the wave, just lost some faith.
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1641. StormJunkie
11:34 PM GMT on July 25, 2007
No ryan, you are part of everyone :~)
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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