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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we now fly 30 percent on AOI
Member Since: Posts: Comments:
Quoting 7544:
did we get 94l yet ?
not yet
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Quoting lilElla:
Sorry to stray off Tropical topic - but there is snow in the forecast and I so look forward to this time year!

For anyone that might like to see what we do on the farm in winter - here you go. This video was taken after we had a freezing rain on top of a foot of snow. Really made for some fast sledding. Sorry but not sure how to link.
Maybe someone can help me with that?

http://www.youtube.com/watch?v=f9rhMA0MmFw


Love the video--and Misirlou was perfect! Thanks for sharing it. It almost makes me wish I was back in the cold and snowy north.

Almost. :-)
Member Since: November 8, 2009 Posts: 4 Comments: 13455
569. 7544
did we get 94l yet ?
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Quoting lilElla:
Good Morning All
#550 - do you think the Winter Storm Watch will be extended East to your area? Brother in Iron Co. might get 8"-10" out of this weekend storm. It's not far away. And the map Orca posted, looks like another Pacific front moving in? We in the North like to say -
"let it snow, let it snow, let it snow"! :)

MODIFIED - at least some of us do :)


Prolly not on going east. We should see a rain/snow mix here and I'm in Marquette.

Let it snow? I dislike cabin fever. 7 months of snow is a bit much for me. If we can make it 6 I might make it this year.
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Sorry to stray off Tropical topic - but there is snow in the forecast and I so look forward to this time year!

For anyone that might like to see what we do on the farm in winter - here you go. This video was taken after we had a freezing rain on top of a foot of snow. Really made for some fast sledding. Sorry but not sure how to link.
Maybe someone can help me with that?

http://www.youtube.com/watch?v=f9rhMA0MmFw
Member Since: Posts: Comments:
Good Morning All
#550 - do you think the Winter Storm Watch will be extended East to your area? Brother in Iron Co. might get 8"-10" out of this weekend storm. It's not far away. And the map Orca posted, looks like another Pacific front moving in? We in the North like to say -
"let it snow, let it snow, let it snow"! :)

MODIFIED - at least some of us do :)
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COMPLETE Tropical Update with INVEST
Member Since: September 2, 2007 Posts: 178 Comments: 20439
I know...........I'm just hoping against hope that it doesn't pan out. Winter is bad enough up here. I don't need FEET of snow to take care of as the first snow of the year.

Thank the lord that model is a 384 hour. Those are really accurate. :)
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Quoting Bordonaro:

Too early in the season, maybe a real bad cold snap series across the US in Jan/Feb 2011..I do not see a 2 week long event this winter..


What the Pacific Northwest really needs is a 2 week cold snap into the -20 to -40 range.

The Mountain Pine Beetle has been devastating the Pine forests.. they say thats what is required to kill them.
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Quoting Orcasystems:


Sorry, not doing snow this year... going to Mexico :)

I am hoping for a replay of Feb 1899

Too early in the season, maybe a real bad cold snap series across the US in Jan/Feb 2011..I do not see a 2 week long event this winter..
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Jeff9641:


Severe Wx outbreak as well if this run would pan out.

Yes, a very BIG one!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:

No, were saving that for you :O)!!


Sorry, not doing snow this year... going to Mexico :)

I am hoping for a replay of Feb 1899
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Quoting Orcasystems:


Snow :)

No, were saving that for you :O)!!

Ha, ha, ha..Looks like interior sections of the NE will get a nice snowstorm, with cold wet heavy snow..
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:
Sunday 11-28-10 @384 HRS, freeze line is across S Central TX..Here it comes....


Snow :)
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Sunday 11-28-10 @384 HRS, freeze line is across S Central TX..Here it comes....
Member Since: August 25, 2009 Posts: 20 Comments: 6785
551. myway
Quoting Neapolitan:
An Arctic blast may be coming next week, but you wouldn't know it right now; according to HAMweather, only seven record low or low maximum temps have been set or tied in the CONUS over the past 24 hours, while 66 record highs or high minimums have been. Some it-doesn't-quite-seem-like-autumn examples from yesterday: 63 in Buffalo, Minnesota; 65 in Hinckley, Minnesota; 76 in Ripley, Tennessee; and a balmy 74 in Lafayette, Indiana.

Over the past three days the high-record/low-record ratio has been 232/53, while over the past week it's been a bit more balanced at 582/360. All in all, the incredibly warm summer in the Lower 48 has morphed into an incredibly warm fall, with some exceptions, of course. From what I've been reading and hearing, however, our seven months of steamy weather may be coming to an end next week; I reckon we'll see...

My family in the north are loving it.
Member Since: May 28, 2008 Posts: 0 Comments: 446
Quoting Jeff9641:



Yup looks like one heck of a Blue Norther is poised to dump south over Thanksgiving. We could be talking temps in the teens and twenties for highs in the Great Lakes region.


I changed the oil on the snowblower a month ago in prep for something like that. If ya haven't thinned your blood by now up here, there is no help for you.

I'd be interested to hear what the good Doc would have to say about the warm LST's for the Lakes this year and what impact it might have. In some years, lake effect is enhanced due to warmer lake temps. Lake Superior was up in the high 60's this year, which is unheard of.
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This is the first time in recorded history that as many as 12 hurricanes have occurred in the Atlantic basin without making U.S. landfall. The States have not seen a hurricane make landfall since the 2004-2005 season, when seven major hurricanes touched down in America.

Overall there were 19 named storms, 12 of those were hurricanes and five of those were major hurricanes.

Link
Member Since: Posts: Comments:
An Arctic blast may be coming next week, but you wouldn't know it right now; according to HAMweather, only seven record low or low maximum temps have been set or tied in the CONUS over the past 24 hours, while 66 record highs or high minimums have been. Some it-doesn't-quite-seem-like-autumn examples from yesterday: 63 in Buffalo, Minnesota; 65 in Hinckley, Minnesota; 76 in Ripley, Tennessee; and a balmy 74 in Lafayette, Indiana.

Over the past three days the high-record/low-record ratio has been 232/53, while over the past week it's been a bit more balanced at 582/360. All in all, the incredibly warm summer in the Lower 48 has morphed into an incredibly warm fall, with some exceptions, of course. From what I've been reading and hearing, however, our seven months of steamy weather may be coming to an end next week; I reckon we'll see...
Member Since: November 8, 2009 Posts: 4 Comments: 13455
Quoting afj3:

I was just getting ready to post to ask that question: when does it get I status?
It could take as long as tomarrow because it is not well organized and the models would be all over the place
Member Since: January 10, 2010 Posts: 0 Comments: 918
Quoting belizeit:
Where do you see it the navy does not have it

Neither does ATCF or the NHC. Soon--in fact, likely this afternoon--but not yet, from what I can see...
Member Since: November 8, 2009 Posts: 4 Comments: 13455
544. afj3
Quoting belizeit:
Where do you see it the navy does not have it

I was just getting ready to post to ask that question: when does it get I status?
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543. Jax82
Vorticity.

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Quoting TampaSpin:
Looks like we have INVEST 94L
Where do you see it the navy does not have it
Member Since: January 10, 2010 Posts: 0 Comments: 918
Looks like we have INVEST 94L
Member Since: September 2, 2007 Posts: 178 Comments: 20439
538. eddye
willit get cold in south fla for thanksgiving
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Click to enlarge
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Some turning associated with the invest..
Member Since: September 27, 2007 Posts: 1 Comments: 20487
Quoting Jeff9641:
2011 could be very very deadly and destructive for the US not only from Hurricanes but I think we are also setting up for one hell of a tornado season.
if not eleven twelve for sure
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Quoting flsky:

Why do you think this?

La Nina maked for an active severe weather season, bringing in our enemy "Mr Wind Shear"!!

Wonderful northwest winds on one side of a trough and a southeast flow on the other=wind shear, turning of winds with height and rotating thunderstorms.
Member Since: August 25, 2009 Posts: 20 Comments: 6785
533. flsky
Quoting Jeff9641:
2011 could be very very deadly and destructive for the US not only from Hurricanes but I think we are also setting up for one hell of a tornado season.

Why do you think this?
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Quoting RitaEvac:


I dont know about the santa claus part

Santa Claus, aka-"Arctic air from the North Pole/Siberia"
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Morning All.

Seems another invest is on the way, 94L.
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GOM temps as a whole dropped pretty sharply the last 3 days. That is one powerful Jet over Bermuda!
I love the drought index, fire weather, and flood watches in Florida. They regularly make no sense.
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Quoting Bordonaro:

Cool a tropical feature and Santa Claus coming to town at the same time :O)!!


I dont know about the santa claus part
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528. Jax82
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Quoting hydrus:
We have the new and improved formula fer yu..:)

That is good :O)!! On Jul 16, 2011 I get to join AARP, I'll be 50, woo-hoo!!

Geritol smoothies anyone???
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:

When you're through with the Geritol, send it to me :O)
We have the new and improved formula fer yu..:)
Member Since: September 27, 2007 Posts: 1 Comments: 20487
Quoting RitaEvac:
Looking at the GFS model long range, it had a massive 1040+mb ridge up in Yukon, with some very cold air up there, if that were to pan out, the lower 48 would get its first arctic blast of the season.

Correct for $1000.00...May I have "CONUS weather" for 1200.00??
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting RitaEvac:
Check out Tequnapeck or whatever its called on the Pacific side, major cool down of the water, weird what strong winds can do to cool off waters

It is probably upwelling from the frequent gales they get there..
Member Since: September 27, 2007 Posts: 1 Comments: 20487
If that pans out, gonna get cold for Thanksgiving and after.
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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.