Is the Atlantic hurricane season getting longer?

By: Dr. Jeff Masters , 1:35 PM GMT on November 11, 2010

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It seems like there have been an unusual number of early and late season tropical storms and hurricanes in the Atlantic in recent years. In 2008, we had four named storms in July, and the second most powerful November hurricane on record. Both 2007 and 2005 had rare December storms, and 2003 featured Tropical Storm Anna, the first April tropical storm ever recorded. This year, Hurricane Tomas made 2010 the fourth straight year with a November hurricane, something that has never occurred in the Atlantic since accurate records began in 1851. The latest runs of the GFS and NOGAPS models are suggesting the possibility that we will have Tropical Storm Virginie in the Caribbean between Colombia and Nicaragua a week from now. Is hurricane season getting longer? Dr. Jim Kossin of the University of Wisconsin published a 2008 paper in Geophysical Research Letters, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is a "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high".


Figure 1. Observed sea surface temperature (SST) trends during the official North Atlantic hurricane season (June-November) for the period 1950-2007. Units are °C per century. The dashed rectangle denotes the tropical storm formation region south of 30° North latitude and east of 75° West longitude. Data are from the NOAA Extended Reconstructed Sea Surface Temperature V3 product [Smith et al., 2008]. Image credit: Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Methods
Dr. Kossin utilized the "best track" database of Atlantic tropical cyclone activity going back to 1851. However, since lack of satellite and aircraft reconnaissance data before 1950 makes the early part of this record suspect, he limited his analysis to the period from 1950 onward. The era of best data--the satellite era beginning in 1980--was also looked at separately, to ensure the highest possible data quality. The area studied was only a portion of the Atlantic--the tropical storm formation region south of 30° North latitude and east of 75° West longitude. This region has shown considerable warming of the Sea Surface Temperatures (SSTs) since 1950, in excess of 1°F (0.6°C) (Figure 1). A statistical method called "quantile regression" was employed. The method looked at how certain thresholds that mark the beginning and end of hurricane season have changed over the years. For example, the date where 5% of all tropical storms form earlier than that date, was called the 0.05 quantile, and the date where 5% of all tropical storms form later than that date, was called the 0.95 quantile. Kossin was able to show that the date of the 0.05 quantile got steadily earlier and the date of the 0.95 quantile steadily got later since 1950. Hurricane season for both the period 1950-present and 1980-present got longer by 5 to 10 days per decade.


Figure 2. Trends in tropical storm formation dates, in the region south of 30° North latitude and east of 75° West longitude, at the 0.05.0.95 quantiles. Trends are based on the periods (left) 1950-2007, and (right) 1980-2007. The dates (month/year) associated with the 0.05, 0.25, 0.50, 0.75, and 0.95 quantiles for each period are shown on the top axis (these threshold dates are based on the full sample for each period). Shading denotes the 90% confidence interval. Image credit: Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Relationship with Sea Surface Temperature
The broadening of the Atlantic hurricane season found was strongly dependent upon Sea Surface Temperatures. Both the onset and end of hurricane season shifted by 20 days per degree C of warming of the SST. With global warming projected to increase tropical Atlantic SSTs 1-2°C by the end of the century, can we then expect a 40-80 day increase in the length of hurricane season? Dr. Kossin doesn't explore this possibility, and doesn't blame the observed increase in the length of the season on human-caused global warming of the oceans. There is reason to believe that future warming of the Atlantic SSTs won't necessarily broaden the area over which tropical storms will form, though. Papers by Henderson-Sellers et al. (1998) and Knutson et al. (2008) theorize that as SSTs warm, the lowest temperature at which tropical storms can form will also increase. The current minimum temperature of 26.5°C (80°F) may increase to 28.5°C for a 2°C warming of Atlantic SSTs. Johnson and Xie (2010) have found observational evidence that the lowest temperature at which tropical storms can form has indeed been increasing at about 0.1°C per decade in the Atlantic, in line with climate model predictions.

References
Henderson-Sellers, A., et al., 1998, "Tropical Cyclones and Global Climate Change: A Post-IPCC Assessment", Bull. Am. Meteorol. Soc. 79, 19–38.

Johnson, N.C., and S.P. Xie, 2010, "Changes in the sea surface temperature threshold for tropical convection", Nature Geoscience doi:10.1038/ngeo1008

Knutson, T.R., J.J. Sirutis, S.T. Garner, G.A. Vecchi, and I.M. Held, 2008, Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions", Nature Geoscience 1, 359 - 364 (2008), doi:10.1038/ngeo202

Kossin, J., 2008, "Is the North Atlantic hurricane season getting longer?", Geophysical Research Letters, Vol. 35, L23705, doi:10.1029/2008GL036012, 2008.

Jeff Masters

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The tropical wave coming off the Coast of Colombia, looks conducive for developement in the Western Caribbean, later this weekend.
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270. JRRP
Quoting Neapolitan:

I would disagree that that's "the same bottom line". The article in Dr. Masters' post stated that the purpose of that paper was only to ask whether the data indicate hurricane seasons are lengthening, and that it wasn't written to delve into matters of climate change. On the other hand, the article which you referenced in #218 states that the science is unsure whether historical hurricane activity has been affected by climate change, and for any number of reasons. The abstract of that article explains very well where the authors are headed, however:

"Whether the characteristics of tropical cyclones have changed or will change in a warming climate %u2014 and if so, how %u2014 has been the subject of considerable investigation, often with conflicting results. Large amplitude fluctuations in the frequency and intensity of tropical cyclones greatly complicate both the detection of long-term trends and their attribution to rising levels of atmospheric greenhouse gases. Trend detection is further impeded by substantial limitations in the availability and quality of global historical records of tropical cyclones. Therefore, it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes. However, future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2%u201311% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6%u201334%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre. For all cyclone parameters, projected changes for individual basins show large variations between different modelling studies."

FWIW, an 11% increase would turn a mid-level Cat 1 into a Cat 2, a mid-level Cat 2 into a Cat 3, and so on up the line.

Yikes...

Link
and then ???????????????????????????????????????
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Quoting KerryInNOLA:
The fish are really biting in the marshes and along the shorelines right now. Speckled trout, big redfish, drum, sheephead, and flounder. Come on down, you'll catch a mess of them.


probably don't need any oil to fry them either....chuckle
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Just out of interest, do you know where I can find archived pressure charts for the UK (eg. from the Met Office)? I'm interested in the tracks and intensities (in pressure - winds are much harder to quantify) of depressions that cross Britain in the average "hurricane" season.


Quoting UKHWatcher:
Getting battered here on the coast right now here in Cumbria UK by 60 mph SW winds straight up the Irish Sea with gusts to 75mph.

Link

We're almost getting more tonight than the CONUS have all season!
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Im pretty pumped, just got accepted to 2 meteorology programs yesterday, and another 1 tonight!

btw... I agree we could get one last storm in SW Caribbean, current SSTs and shear conditions could allow for a marginally strong storm to develop.
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Not sure... A quick search on google & the Met gave not much hint however I learnt that most countries (USA aside) use a 10 minute average.

Not sure whether the US are following the Mother country or leading on that though!
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Quoting KEEPEROFTHEGATE:
i only have 4 years to go to achieve gold level with my union membership the highest you can go


I retired from the Military in 98 with 22 years in, at the age of 39... just waiting for SWMBO to reach 55 so she can retire.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Complete Update






TSPIN BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting DontAnnoyMe:
Low in SW Carib days 6 & 7?



Certainly possible. The GFS, ECMWF, and NOGAPS have all been hinting at some possible cyclogenesis in the southern Caribbean.
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St Bees 10 miles North of us Link

We did have fun 'car-sailing' by opening the passenger doors in the wind down at the beach car park earlier I must say!
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Winds are not abating here either: Latest Observations in Capel Curig, 56 mph sustained, 89 mph gusts. I live in Bangor at the Menai Straits, where gusts of 70 mph were recorded.

UKHWatcher, do you know what sustained means in the UK, 1 min average, 3 min or 10 min?
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Low in SW Carib days 6 & 7?



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Quoting Jeff9641:


I agree with that! 2011 with nuetral conditions are a recipe for disaster somewhere. Could be a 2008 next season!


La Nina is expected...
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Quoting Orcasystems:


Only 4 left here :)
i only have 4 years to go to achieve gold level with my union membership the highest you can go
Member Since: July 15, 2006 Posts: 171 Comments: 53809
Getting battered here on the coast right now here in Cumbria UK by 60 mph SW winds straight up the Irish Sea with gusts to 75mph.

Link

We're almost getting more tonight than the CONUS have all season!
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
ya got me for eight more years yet till i retire at 55


Only 4 left here :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting Orcasystems:


I'm sorry buds.. but you really have to get out of the Centre of the Universe and go smell the flowers.
ya got me for eight more years yet till i retire at 55
Member Since: July 15, 2006 Posts: 171 Comments: 53809
248. Orcasystems 10:59 PM GMT on November 11, 2010
Quoting KEEPEROFTHEGATE:
it not to get anything faster its for me i run it on a 33 inch flat screen and during busy times i could have as many as 25 tabs running on my screen so to keep it up to speed it takes a lot


I'm sorry buds.. but you really have to get out of the Centre of the Universe and go smell the flowers.



Quoting PrivateIdaho:
Be sure to put nice rims on it and have it lowered. :)
the building is also considering upgrading to an internet ready wireless cam system with 18 cams running all at the same time and i need to be able to access that as well to watch activites within the high rise i manage so with the cams and my weather hobby i am gonna need lots of mem for everything to work when needed
Member Since: July 15, 2006 Posts: 171 Comments: 53809
Quoting KEEPEROFTHEGATE:
it not to get anything faster its for me i run it on a 33 inch flat screen and during busy times i could have as many as 25 tabs running on my screen so to keep it up to speed it takes a lot


I'm sorry buds.. but you really have to get out of the Centre of the Universe and go smell the flowers.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
I Have trouble downloading the 18z gfs could someone post some images of it or doesn't it show the tropical system this week end
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Quoting KEEPEROFTHEGATE:
sorry TX i run 255 gb system with dsl high speed internet/ethernet connection i am considering upgrading to fibre optic connection by next cane season
Be sure to put nice rims on it and have it lowered. :)
Member Since: August 29, 2010 Posts: 0 Comments: 5236
Quoting DoverWxwatchter:
And one thing you can do to speed up your computer is to defrag it once a month. Probably more effective than any of that 'cleanup' software.


Disagree, defragging will only help speed up starting the pc and programs, and minimally at that. What will help browsers the most is clearing the cache, history, and cookies once a day.
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Quoting WXTXN:
Wow Fiber? You should be able to get all of the advisories a few milliseconds before the rest of us. LOL I'm not trying to be mean.
it not to get anything faster its for me i run it on a 33 inch flat screen and during busy times i could have as many as 25 tabs running on my screen so to keep it up to speed it takes a lot
Member Since: July 15, 2006 Posts: 171 Comments: 53809
241. WXTXN
We had three storms effect us here in South Texas with two deaths and I'm still dodging all of the potholes from the flooding. Maybe no one got a direct hit but the US had more effects than just hampering the oil clean up effort.
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237. You know I hate these kind of articles that only focus on US impacts in a hurricane season..
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236. WXTXN
Wow Fiber? You should be able to get all of the advisories a few milliseconds before the rest of us. LOL I'm not trying to be mean.
Quoting KEEPEROFTHEGATE:
sorry TX i run 255 gb system with dsl high speed internet/ethernet connection i am considering upgrading to fibre optic connection by next cane season
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Quoting WXTXN:
I have a Mac on DSL pretty slow but I have no problem streaming videos and other bandwidth intensive stuff. It's just all the loops on this blog that seem to stump my computer...


Another tip is to drag your last url address of this blog into a new tab... That way you liberate all the past history that you build up with the refresh button.... Your antivirus / firewall and antispyware is important
Member Since: August 2, 2010 Posts: 21 Comments: 9814
234. WXTXN
I have a Mac on DSL pretty slow but I have no problem streaming videos and other bandwidth intensive stuff. It's just all the loops on this blog that seem to stump my computer...
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Past couple of runs of the ECMWF long-range have been hinting a cold push of air funneling down from Canada the week of Thanksgiving. Teleconnections of the EPO and the NAO diving negative favors a cold air outbreak. This mornings 00z ECMWF featured a massive 1054mb Canadian High most likely progged to head south and east bring with it cold air advection for the eastern 2/3rds of the CONUS. And if you notice there is a low pressure system off the coast of New England.



Figure 1. ECMWF 00z 850MB temperatures with sea level pressure plot.



Figure 2. ECMWF 12z 850mb temperatures with sea level pressure plot.



Figure 3. Model plots of the NAO




Figure 4. Model plots of the EPO
Member Since: October 28, 2006 Posts: 57 Comments: 30489
My Prediction is 2011 will be 2010 like in storms but completely different in tracks.

My Cities I Predict For Impact By Storms Next Year Are:

Corpus Christi, TX
Jacksonville, FL
Wilmington, NC
Miami, FL
Tampico, MX
Houston, TX
Brownsville, TX
Tampa/St. Petersburg, FL
Cancun, MX
Cozumel, MX
San Juan, PR
Pensacola, FL
FL KEYS, FL

This is just a prediction. Don't Snap At me For Putting Your Cities, I Just Feel These Areas Might Be Affected Next Season.

My Prediction For 2011 Season:
14 to 19 Storms
6 to 11 Hurricanes
3 to 7 Major Hurricanes

November Predictions For 2010 Season:
2 named storms
1 hurricane
0 major hurricanes
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230. WXTXN
Thanks yall for the tips on speeding up my blogging experience!
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Quoting WXTXN:
You too Keeper
sorry TX i run 255 gb system with dsl high speed internet/ethernet connection i am considering upgrading to fibre optic connection by next cane season
Member Since: July 15, 2006 Posts: 171 Comments: 53809
IMO May 15 - Nov. 30th should be the new date.

Last time we've gotten a post-season storm was Olga in 2007.. nearly 3 years ago.

2005, 2004, 2003 all saw post season storms and I wouldn't be surprised if 2010 saw one.
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My guess is that we will see the hurricane seasons go from MAY 20 to DECEMBER 10 in about 3 to 5 years, well at least the official beginning and end will.

Who's Ready for the offseason!!!!
SAY I!


I!
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Quoting hcubed (#218):
While we're waiting for that last, how about this article?

Nature Geoscience 3, 157 - 163 (2010)
Published online: 21 February 2010 doi:10.1038/ngeo779

Subject Categories: Climate science; Atmospheric science

Tropical cyclones and climate change

Thomas R. Knutson, John L. McBride, Johnny Chan, Kerry Emanuel, Greg Holland, Chris Landsea, Isaac Held, James P. Kossin, A. K. Srivastava & Masato Sugi

....................

Another RECENT study, then, stating the same bottom line.

I would disagree that that's "the same bottom line". The article in Dr. Masters' post stated that the purpose of that paper was only to ask whether the data indicate hurricane seasons are lengthening, and that it wasn't written to delve into matters of climate change. On the other hand, the article which you referenced in #218 states that the science is unsure whether historical hurricane activity has been affected by climate change, and for any number of reasons. The abstract of that article explains very well where the authors are headed, however:

"Whether the characteristics of tropical cyclones have changed or will change in a warming climate — and if so, how — has been the subject of considerable investigation, often with conflicting results. Large amplitude fluctuations in the frequency and intensity of tropical cyclones greatly complicate both the detection of long-term trends and their attribution to rising levels of atmospheric greenhouse gases. Trend detection is further impeded by substantial limitations in the availability and quality of global historical records of tropical cyclones. Therefore, it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes. However, future projections based on theory and high-resolution dynamical models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms, with intensity increases of 2–11% by 2100. Existing modelling studies also consistently project decreases in the globally averaged frequency of tropical cyclones, by 6–34%. Balanced against this, higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre. For all cyclone parameters, projected changes for individual basins show large variations between different modelling studies."

FWIW, an 11% increase would turn a mid-level Cat 1 into a Cat 2, a mid-level Cat 2 into a Cat 3, and so on up the line.

Yikes...
Member Since: November 8, 2009 Posts: 4 Comments: 13526
Quoting sunlinepr:


Sure it won't accelerate internet connection, but it will optimize your browser, eliminating temp files, cookies, and all the digital garbage you get from browsing. It will also optimize the registry eliminating broken links.... Excellent freeware....

Well I eliminated a couple of my posts.... the ESC key tip is super...


Also need to consider that likely there are folks with older - i.e., slower computers, which can't be sped up no matter how clean they are.

Another thing one could do is to choose not to load images automatically.
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Quoting DontAnnoyMe:


Using that might be a good idea in general, but it will not help to speed up a slow connection. Even DSL can be slow; there are several DSL speeds. And there are still a lot of people who don't even have DSL.


Sure it won't accelerate internet connection, but it will optimize your browser, eliminating temp files, cookies, and all the digital garbage you get from browsing. It will also optimize the registry eliminating broken links.... Excellent freeware....

Well I eliminated a couple of my posts.... the ESC key tip is super...
Member Since: August 2, 2010 Posts: 21 Comments: 9814

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