Stronger SST-intense hurricane link?

By: Dr. Jeff Masters , 2:53 PM GMT on April 12, 2006

A link between global warming and increased intense hurricane activity is a very hot topic in hurricane research right now, and many new papers on the subject will be published this year. The latest paper, published March 15 in the on-line version of Science, Science Express, finds stronger evidence that the increasing number of Category 4 and 5 hurricanes globally since 1970 is directly linked to increases in Sea Surface Temperature (SST). The paper by Hoyos et al. was called, "Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity". Two of the co-authors--Peter Webster and Judith Curry of Georgia Tech--were also authors of a paper published in Science magazine in 2005 that reported a worldwide increase in the number of Category 4 and 5 hurricanes of 80% in the past 30 years. The paper, (Webster et al., 2005), titled "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", linked the rise in storms to increasing sea surface temperatures and concluded that "global data indicate a 30-year trend toward more frequent and intense hurricanes." As I reported in my blog on the subject, their findings should be considered as preliminary evidence that the global incidence of Category 4 and 5 hurricanes may be increasing. There are some severe problems with the quality of the data set used to, and there are good reasons to believe that the actual increase in Category 4 and 5 hurricanes is far lower than the 80% increase found by Webster et al.

The new paper by Hoyos et al. uses a mathematical technique called information theory to study the relative effects of SST, wind shear, humidity, and wind patterns on global incidence of Category 4 and 5 hurricanes. The study found that only SST can explain the observed increase in these storms. One thing I like about the new study is that it directly addesses the issue of data quality in the record of Category 4 and 5 hurricanes, something the authors neglected to do in their previous paper. The authors write, "Recently, the quality of the hurricane data has been questioned and even a reanalysis of the tropical cyclone databses has been suggested in order to ratify that the results of recent studies are not due to problems in the data." The authors go on to say that they performed their analysis without using suspect data from the North Indian Ocean, and found no difference in their results. Well, that's not too surprising, since the number of Category 4 and 5 hurricanes in that ocean basin represents only about 2% of the global total. What I would have liked to have seen was the analysis re-done using the latest reanalyzed results for typhoons from the Western Pacific, which accounts for 48% of global Category 4 and 5 hurricanes. In a paper accepted for publication but not yet finalized, Knaff and Zehr (2006) make convincing arguments that typhoon intensities during the 1973-1986 period were too low due to measurement error, and the number of Category 4 and 5 storms in the region have been roughly constant for the past 50 years. Dr. Knaff and Charles Sampson have performed a preliminary re-analysis of maximum typhoon intensities for the period 1966-1987 based on the Knaff and Zehr (2006) results. In a paper to be presented at the upcoming 27th Conference on Hurricanes and Tropical Meteorology (April 24-28, 2006), they show that after correcting for the measurement errors, the number of Category 4 and 5 typhoons during the 1966-1987 period increased by 1.5 per year, leaving only a slight upward trend in Category 4 and 5 typhoons during the period 1970 - 2004. The 16% increase in Category 4 and 5 typhoons found by Webster et al. during the past 15-year period is reduced to just 3%. I suspect that if the information theory techniques of Hoyos et al. were applied to this modified data set, the connection between SST and an increase in global Category 4 and 5 hurricanes would be much weaker.

The blog has more information on the paper, along with links to quotes in the media from many of the scientists involved in the hurricanes/global warming debate.

My next blog will be on Friday. Apparently, NHC has "found" a new Atlantic subtropical storm that formed in 2005, bringing the total for the season to 28 named storms. If the final report on this new storm has been issued, I'll discuss that.

Jeff Masters

Hoyos, C.D., P.A. Agudelo, P.J. Webster, and J.A. Curry, "Deconvolution of the Factors Contributing to the Increase in Global Hurricane Intensity",, 16 March 2006, 10.1126/science.1123560.

Knaff, J.A., and R.M. Zehr, "Reexamination of Tropical Cyclone Wind-Pressure Relationships", accepted to Weather and Forecasting, 2006.

Webster, P.J., G.J. Holland, J.A. Curry, and H.-R. Chang, "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment", Science, 309, 1844,1846, 16 September 2005.

Alpha Chi Omega missing a wall (Arian)
The twister tore a whole wall from the sorority house and detroyed everything around it.
Alpha Chi Omega missing a wall

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256. weathergeek5
1:18 PM GMT on April 19, 2006
I am a college student doing a research paper on the hot topic between global warming and hurricanes. DR William Gray says the globe has been warming but not to the extent that the global warming scientists make it out to be. He says greenhouse gases were increasing from 1970-1994. How come the Atlantic was in a cool AMO then? Also what are the characteristics that cause the warm and cold AMO?

Reference: Weather Seer: We’re Lucky. (2005). Discover. Sept2005. Vol.26 Issue 9. p15-16.
Retrieved March 17, 2006 from EBSCOhost database. [Magazine Article from
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255. rwdobson
2:24 PM GMT on April 14, 2006
fact is, either tunnels or tubes or whatever would be:

a) hugely expensive with no certainty of getting any benefit
b) very likely to cause negative side effects
Member Since: June 12, 2002 Posts: 0 Comments: 1653
251. louastu
3:04 AM EDT on April 14, 2006
There is a Moderate Risk of severe weather tomorrow for portions of Nebraska and Iowa.
250. louastu
3:02 AM EDT on April 14, 2006
I am barely outside the tornado watch area.
249. louastu
3:00 AM EDT on April 14, 2006
Tornado Watch for portions of Illinois and Indiana.
248. louastu
2:36 AM EDT on April 14, 2006
I am getting a very nice light show right now.
246. Inyo
6:23 AM GMT on April 14, 2006
why would global warming decrease the number of hurricanes? increased shear? more intense hurricanes leading to more efficient cooling of water and shadowing or absorbing small ones?
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245. acduke
6:12 AM GMT on April 14, 2006
I'm not sure if anyone has posted on this yet.

Apparently the U.S. and Taiwan have joined forces to use the bend in GPS signals as they pass through the atmosphere to get high resolution picture of what's going on in the atmosphere down to about 1500ft above the surface. This would enable readings over open oceans where there are none now, with the possibility of increasing computer model forcast accuracy for every corner of the earth.

Here's a optimistic quote and a link to the article on

"'I am very excited about the project. The planning for this started in the fall of 1997. Nine years have passed since then. I firmly believe that COSMIC will revolutionize atmospheric remote sensing for weather prediction, climate monitoring, and space weather forecasting. GPS radio occultation technique is very accurate, of high vertical resolution, and is also very cost-effective,' Kuo said."


Hopefully this thing makes it off the launch pad in one piece. What are your thoughts on this project Dr. Master, or anyone else?

- acduke
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243. Skyepony (Mod)
4:59 AM GMT on April 14, 2006
Tornadoes Reported Across Eastern Iowa
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242. Skyepony (Mod)
4:02 AM GMT on April 14, 2006
agreed~ we've messed with mother nature enough. What would the effects of the salinity of the 1km depth be to the enviroment of the surface? Also notice on the 1000m that to go that deep, you can't obtain water around the populated areas where hurricanes generally roam. & cooler ocean temps could be bad for tourism.
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241. taco2me61
3:53 AM GMT on April 14, 2006
I just do not like the idea of cooling the SST... Now we here like to get in the GOM when it has warmed to 80 plus degrees, and if they cool the water not only will the marine life have problems but it could cause damage to the reefs that are out there... Now I fill very strong about that and they should not mess with Mother Nature if you know what I mean...
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239. Skyepony (Mod)
2:14 AM GMT on April 14, 2006
Dr Masters~ Any reports back from the up coming conference would interesting...

A few presentations that caught my eye~

Tropical cyclone climatology in a global warming climate as simulated in a 20km–mesh global atmospheric model stating~

A comparison of the experiments suggests that the tropical cyclone frequency in the warm-climate experiment is globally reduced by about 30% (but increased in the North Atlantic) compared to the presentday-climate experiment. Furthermore, the number of intense tropical cyclones increases. Some of the papers in your blog mention the increase in North Atlantic storms but baffled as to why. I've seen no con on the other side, so that data is good? & does this article as to why really hold the answers?

Could hurricanes form from random convection in a warmer world?

Precursor climate aspects of the 2005 Atlantic hurricane season

& of course A device to control sea surface temperature and effects on hurricane intensity The pump idea using the wave action is ingenious, allowing the bottom of the "tube" to be 1km deep, not dependant on a gulf stream, for bringing cooler water to the surface than say the tunnels. Though I couldn't support the idea of tubes in the sea.

Right after the tubes 3:30 PM-5:15 PM, Monday, Regency Grand Ballroom~ Gray & Emmanuel, back to back on the globial warming & hurricanes issue. Wish they felt they could remain civil enough to agree to a debate. Could set an example of how this all can be discussed without getting out of hand.

Wow...hard choices as to where to spend your time.
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237. louastu
11:05 PM EDT on April 13, 2006
Obviously, when it comes to severe weather, a lot more research is needed.
236. louastu
11:03 PM EDT on April 13, 2006
Only a 5% risk in that area and they have 15 tornado reports.
235. louastu
11:01 PM EDT on April 13, 2006
I don't find that as interesting as this.

232. louastu
10:43 PM EDT on April 13, 2006
Here are the wind reports for Cook County in Illinois, from March 12.

0648 70 TINLEY PARK COOK IL 4157 8780 171ST AND HARLEM (LOT)
0650 60 MELROSE PARK COOK IL 4190 8786 (LOT)
231. louastu
10:31 PM EDT on April 13, 2006
Well, if I remember correctly, the last time this happened, the first storms weakened prior to reaching the lakes, and then later in the day, Chicago was slammed with 70 mph winds.
228. louastu
10:05 PM EDT on April 13, 2006
There have been 8 tornado reports, and also a report of 4.25 inch diameter hail.

227. HurricaneMyles
2:02 AM GMT on April 14, 2006
Well nvm, it's lowered down to 3 inch diameter now. Still nothing to scoff at, though. There's a couple of severe weather watches so I guess it's possible that more thunderstorms will develope.
Member Since: January 12, 2006 Posts: 5 Comments: 827
226. HurricaneMyles
1:59 AM GMT on April 14, 2006
Wow, NEXRAD says one of the cells in that thunderstorm cluster is producing greater then 4 inch hail. Hope those people are safe out there.
Member Since: January 12, 2006 Posts: 5 Comments: 827
225. louastu
9:50 PM EDT on April 13, 2006
I think that when we are in a La Nina phase, wind shear values are usually lower than normal. This provides a more favorable enviroment for hurricanes to develop.
224. HurricaneMyles
1:50 AM GMT on April 14, 2006
La Nina causes causes many changes in seasonal climate around the world. One seasonal change is that when La Nina is present during the N. Hemisphere summer it causes lower then normal levels of shear across the Atlantic. This generally causes a more active season then ussual.
Member Since: January 12, 2006 Posts: 5 Comments: 827
223. louastu
9:42 PM EDT on April 13, 2006
Posted By: ForecasterColby at 1:10 AM GMT on April 14, 2006.
What you're looking at is a graph of several factors of tropicalness (is that a word?).

I checked to see if "tropicalness" is a word, and the answer is no. Having said that, no one on this site cares whether you are making up new words. As far as I'm concerned, it is completely acceptable.
222. Weather456
1:28 AM GMT on April 14, 2006
What does la Nina have to do with Hurricane Seasonal Activity
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221. louastu
9:06 PM EDT on April 13, 2006
This is the hail forecast for tonight.

And this is the wind forecast.

I am in the 30% risk area for both hail, and wind.
220. ForecasterColby
1:10 AM GMT on April 14, 2006
"I hope something is mentioned about my tunnel idea there!!"

I give the disturbance more chance.

What you're looking at is a graph of several factors of tropicalness (is that a word?). The lines are by time, A is the cyclone's start, C is current, and Z is end of cyclone or model run.
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219. HurricaneMyles
1:06 AM GMT on April 14, 2006
LOL, last word should be 'sea' not 'see'.

But anyways, I hope that this year's dry Spring doesn't fortell the coming hurricane season. It's unlikely that we'll have 20 or more storms, but you only need one in your area for it to matter to you.
Member Since: January 12, 2006 Posts: 5 Comments: 827
218. HurricaneMyles
12:58 AM GMT on April 14, 2006
Dry Florida Springs and higher chance of landfall is not really a coincidence. It is partly because of the La Nina's influence on dry springs and active hurricane seasons. Obviously an active hurricane season gives a higher chance of a landfall over a inactive season.

Also, another reason for dry Springs in Florida more specific then just 'La Nina' is that dry weather means high pressure is consitantly in control and low pressure troughs cannot bring us moisture outside the rainy season. During the heart of summer/rainy season, moist high pressure leads to afternoon thunderstorms. But until Late May/Early June the high pressure system is too dry for rain. However, a consitant high pressure system over the East Coast early in the year leading to a dry Spring ussually correlates to the same high pressure system over the East Coast during hurricane season, and a higher chance of landfall since theres less chance of recurvature

I hope that explains to some why dry Springs normally correlate with a higher then likely chance of landfall instead of recurving back out to see.
Member Since: January 12, 2006 Posts: 5 Comments: 827
217. louastu
8:58 PM EDT on April 13, 2006
The storms in Iowa (about to cross into Illinois) are looking pretty strong. There are a couple of tornado warnings with them right now.
214. FloorManBroward
8:45 PM EDT on April 13, 2006
When South Florida gets less than 1 inch of rain in May they usually get a hurricane.Nobody knows if that is a coincidence or not.
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213. Trouper415
12:29 AM GMT on April 14, 2006

I'm no expert but to answer your question about the dry spring having an effect on the hurricane season does correlate. For in the spring, the La Nina pattern which we are experiencing is causing the lack of rainfall in that area. La Nina years are also typical for bringing above normal hurricane activity to the Atlantic Basin. So you are correct.

Giants in 06
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212. SMU88
12:26 AM GMT on April 14, 2006
Colby...please explain to me what I am looking at in your link.
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211. bocaman
12:22 AM GMT on April 14, 2006
yeah that disturbance will be a distant memory soon, no rain for south florida from it.
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210. SMU88
12:24 AM GMT on April 14, 2006
Anyway have an answer to this question:

I remember reading somewhere that if South Florida has a dry March? April? May? that then there is a higher chance that South Florida will have a this true?
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209. ForecasterColby
12:25 AM GMT on April 14, 2006
*raises hand*

Take a look at this! Link
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206. louastu
6:03 PM EDT on April 13, 2006
Wow, I thought 81 was bad, but that is rediculous.

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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