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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322. CaribbeanWave
3:01 AM GMT on November 12, 2010
Flooding in the US Virgin Islands on the Island of St. Croix


Member Since: July 17, 2008 Posts: 0 Comments: 78
321. Bordonaro
3:00 AM GMT on November 12, 2010
Quoting washingtonian115:
Crap that's right over my area.......

The National Weather Service in Ft Worth, TX mentioned this at 9:37PM CST on 11-10-10 in the Area Forecast Discussion.

Whenever the mention these two words "Polar Vortex" in a forecast discussion, it is going to get very freaking cold!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
320. PSLFLCaneVet
2:46 AM GMT on November 12, 2010
Quoting flsky:

Gotcha beat! I retired from UCLA at 50!


Good evening Sky. How are you?
Member Since: July 23, 2010 Posts: 1 Comments: 12414
319. Orcasystems
2:40 AM GMT on November 12, 2010
Complete Update






TSPIN BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
318. washingtonian115
2:35 AM GMT on November 12, 2010
Quoting Bordonaro:
Long Range 384 HRS 11-27-2010..GFS 10M wind/surface temps..One heckuva cold blast..
Crap that's right over my area.......
Member Since: August 14, 2010 Posts: 10 Comments: 16971
317. washingtonian115
2:28 AM GMT on November 12, 2010
I think in 2011 that the u.s will see a higher impact of storms than this year.The carribean really needs a break but I don't think thats happening unless shear sets up over the carribean for the year(I don't think so considering we'll be in La nina/neutral conditions).But alot of people said the same thing for 2010 for the u.s so we'll see.....And the hurricane predictions for next year should be coming out next month.Would be interesting to see what the experts think.But I think they'll agree that it will indeed be active looking at weather patterns and the models.
Member Since: August 14, 2010 Posts: 10 Comments: 16971
316. Bordonaro
2:28 AM GMT on November 12, 2010
Long Range 384 HRS 11-27-2010..GFS 10M wind/surface temps..One heckuva cold blast..
Member Since: August 25, 2009 Posts: 20 Comments: 6785
315. Quadrantid
2:11 AM GMT on November 12, 2010
Quoting Neapolitan:

That's a great image. I like the moon, of course, but also the way Freeport (left) and Nassau (right) shine out in the Bahamas, and how bright Atlanta at the far left of the photo is, and how the lights of New York and Philadelphia and Boston and Washington, D.C., have set the atmosphere aglow. (FWIW, I live near the southern edge of the sliver running down the west side of the peninsula.)


A beautiful image, but seeing light pollution like that makes me weep. As an astronomer, I'm fortunate enough to have been out under truly dark skies - and so I've seen the sights that are lost to pretty much everyone in the developed world thanks to the curse of poorly designed lighting :(

Simply fitting internal reflectors in street lights would ensure that the great majority of their light would head down, rather than up (most modern streetlights waste something like 30% of their energy illuminating the night sky). We'd save energy, better illuminate our streets, and make a start returning to properly dark skies.

The problem is exacerbated by all these people who have crazy 500W garden "anti-burglar" lights/security lights. They're insane. All they do is throw so much light that you're dazzled when you look out, and cast shadows so dark it's trivial for a mugger/burglar to hide in perfect safety while you, the victim, is perfectly lit approaching them.

Sorry -- it's a pet peeve of mine -- so few people these days get to see the splendour of the milky way, or see the zodiacal light, the Andromeda galaxy, and the general beauty of a properly dark sky -- and yet the one type of pollution we still do nothing to diminish or legislate against is light pollution. If my neighbour has their music on too loud at 3am, so I can't sleep, I have legal recourse. If they have a security light so bright I can't sleep, there's typically nothing I can do.

That all said, light pollution does make the surface of the planet look pretty stunning from the air -- night landings in big cities are always spectacular -- but it's always depressing thinking just how much energy is being wasted, thrown in the sky to do nothing but fill it with glow and glare, hiding what we really should be able to see...
Member Since: June 13, 2009 Posts: 0 Comments: 106
314. Neapolitan
1:50 AM GMT on November 12, 2010
Quoting TropicalAnalystwx13:
If you guys didn't know, Lisa was updated for best track...She now stands at:

85 mph/982 mb.

She was...

80 mph/987 mb.


Along those same lines, the NHC's KMZ (Google Earth) file for Hurricane Igor now has him listed as a 925 mb/155-knot Cat 5 for a single TWO (9/15 @ 0000 UTC). Be interesting to see whether that holds up when the TCR is released here soon...
Member Since: November 8, 2009 Posts: 4 Comments: 13527
313. HurricaneDean07
1:49 AM GMT on November 12, 2010
im checking out early tonight, nite all.
Member Since: October 3, 2010 Posts: 40 Comments: 4129
312. taistelutipu
1:46 AM GMT on November 12, 2010
thanks for the inspiration Kerry. I'm going to have fish for dinner. I'm off for tonight. See you all tomorrow.
Member Since: August 20, 2007 Posts: 12 Comments: 639
309. TropicalAnalystwx13
1:40 AM GMT on November 12, 2010
If you guys didn't know, Lisa was updated for best track...She now stands at:

85 mph/982 mb.

She was...

80 mph/987 mb.
Member Since: July 6, 2010 Posts: 113 Comments: 32023
308. TropicalAnalystwx13
1:39 AM GMT on November 12, 2010
I believe we'll stay La Nina through at least September of next year.

However, if we do indeed transition to a Neutral at some point before that, it will only make the season even more active.

I'm predicting 11-19 NS
Member Since: July 6, 2010 Posts: 113 Comments: 32023
307. PensacolaDoug
1:38 AM GMT on November 12, 2010
Just got home from the "Night Airshow" at Pensacola NAS. Absolutely AWSOME!
Member Since: July 25, 2006 Posts: 0 Comments: 563
305. DontAnnoyMe
1:34 AM GMT on November 12, 2010
Quoting CybrTeddy:
280. Interesting, given this says La Nina well into July.


"Consistent with nearly all ENSO forecast models (Fig. 6), La Niña is expected to last at least into the Northern Hemisphere spring 2011. A large majority of models also predict La Niña to become a strong episode (defined by a 3-month average Niño-3.4 index of –1.5°C or colder) by the November-January season before gradually weakening. A few of the models, including the NCEP Climate Forecast System (CFS), suggest that La Niña could persist into the Northern Hemisphere summer 2011. However, no particular outcome is favored beyond the Northern Hemisphere spring due to large model disagreement and lower model skill during the period."

Link
Member Since: September 21, 2010 Posts: 1 Comments: 3690
304. Neapolitan
1:31 AM GMT on November 12, 2010
One of the best articles I've read regarding today's celebratory holiday.

Bumper-Sticker Patriotism Is No Way to Honor Our Veterans

And before anyone jumps on me for my "typical liberal stance", you should know I am a non-combat veteran of the USAF. ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13527
303. HurricaneDean07
1:28 AM GMT on November 12, 2010
Quoting TropicalAnalystwx13:


La Nina is expected...
Pretty sure it will start as La Nina and convert into a neutral event.

I'll Have A Tracking Map On It Later....
Member Since: October 3, 2010 Posts: 40 Comments: 4129
302. flsky
1:27 AM GMT on November 12, 2010
Quoting KEEPEROFTHEGATE:
ya got me for eight more years yet till i retire at 55

Gotcha beat! I retired from UCLA at 50!
Member Since: October 24, 2006 Posts: 0 Comments: 1956
301. outlookchkr
1:24 AM GMT on November 12, 2010
Quoting Neapolitan:

That's a great image. I like the moon, of course, but also the way Freeport (left) and Nassau (right) shine out in the Bahamas, and how bright Atlanta at the far left of the photo is, and how the lights of New York and Philadelphia and Boston and Washington, D.C., have set the atmosphere aglow. (FWIW, I live near the southern edge of the sliver running down the west side of the peninsula.)
I like the Keys, a very interesting sliver...............
Member Since: October 28, 2010 Posts: 0 Comments: 65
Quoting Skyepony:

Before May I told ya'll this extreme La Nina was coming.


Yes, you did...and nice work that was. ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13527
299. Skyepony (Mod)
Quoting JRRP:

i remember that on may the models showed a weak niña at this time


See the Black line with squares on the bottom, coming near -2? That is the dynamical NASA GMAO.. that's the 2nd model graph I posted in comment #280. Before May I told ya'll this extreme La Niña was coming.

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Quoting flsky:

Fascinating image! Interesting to see how much of the state is rural or uninhabited.

I personally would rather see less light.: )
Member Since: August 19, 2008 Posts: 0 Comments: 1701
296. flsky
Quoting KerryInNOLA:
No oil in them. Gulf seafood is the safest in the world because it has been tested so heavily. And it tastes great. My favorite is stuffed baked flounder.The flounder is tender and sweet and the lump crabmeat with shrimp on top is fantastic. With a side of cajun potato salad and a root beer, you are in heaven. And don't forget the garlic french bread.

I'd gladly eat whatever you could send to the Daytona area, but it's gotten so expensive! More than beef these days. Sheesh!
Member Since: October 24, 2006 Posts: 0 Comments: 1956
295. JRRP
Quoting Skyepony:


I have to disagree.. across the board 2/3rds the models have Neutral or warmer. (click pic to make bigger)


Looking beyond the models a moment.. The end is in sight...clouds have returned to the mid & high latitudes. This should give us a much stronger Polar vortex this winter than we saw last..kicking up some K-waves & slackening the Pacific trade winds causing the collapse of La Nina. Expecting a Dec-Jan peak, near -2, followed by neutral conditions around April-may. After that depends on how strong a polar vortex gets going this winter. If it's strong & mostly undisrupted we may trip into weak el nino conditions around July. If it is weaker & troubled, La Nina would be slower to go & we'd probably see the warm side of neutral for 'cane season next year. The extreme upwelling from this strong La Nina should really feed the vortex clouds & moisture but the extreme Arctic melt makes the vortex less stable.. Dynamical models concur..

i remember that on may the models showed a weak niña at this time
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294. flsky
Quoting CaicosRetiredSailor:
Florida from the ISS



Posted on November 2, 2010
by Astro_Wheels


http://twitpic.com/3338m8

Fascinating image! Interesting to see how much of the state is rural or uninhabited.
Member Since: October 24, 2006 Posts: 0 Comments: 1956
Quoting doorman79:


I know, and thats not Grothar :p


That's the joke. We get each other all the time.
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292. Skyepony (Mod)
Quoting CybrTeddy:
280. Interesting, given this says La Nina well into July.




That is one model of many.. it is the dark blue with squares on the first graph I posted & probably why NOAA (it's the NCEP/NWS model) is only saying that La Nina should last to the start of spring, which near all agree on.

Another approach to this is comparing current years.. we are down to only 3 other comparable years now & we are ahead of all of them in the dive..will we bottom lower than -2? It would just make for a stronger polar winter vortex & an outside chance at El Niño. Notice though 2 of the 3 head into neutral conditions for most the next 'cane season.


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Quoting GeoffreyWPB:


Grothar and I are very good friends.


I know, and thats not Grothar :p
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Quoting doorman79:


Poor dude :(


Grothar and I are very good friends.
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Happy Veterans Day Evening

Semper Fi



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Quoting GeoffreyWPB:
Happy Veterans Day to all of our brave and dedicated service men and woman. I celebrated with my good friend Grothar down in Ft. Lauderdale....Here is a brief clip:



Poor dude :(
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and I forgot to add to my previous post that the systems with a link, currently Annette to Heike in 2010, come with a synopsis but unfortunately only in German, I'm afraid. Click on the name to read it.

And another edit: The graphics archive goes back to October 13 2002. There are no surface pressure charts before this date, only the list of names with the date of their christening.
Member Since: August 20, 2007 Posts: 12 Comments: 639
Quoting CaicosRetiredSailor:
Florida from the ISS


The Florida peninsula and the southeastern U.S. on the kind of evening that I miss most about our planet. A clear autumn night with moonlight over the water and the sky filled with a billion stars.

Posted on November 2, 2010
by Astro_Wheels


http://twitpic.com/3338m8

That's a great image. I like the moon, of course, but also the way Freeport (left) and Nassau (right) shine out in the Bahamas, and how bright Atlanta at the far left of the photo is, and how the lights of New York and Philadelphia and Boston and Washington, D.C., have set the atmosphere aglow. (FWIW, I live near the southern edge of the sliver running down the west side of the peninsula.)
Member Since: November 8, 2009 Posts: 4 Comments: 13527
Happy Veterans Day to all of our brave and dedicated service men and woman.
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Happy Veterans Day!

A big THANK YOU! to all who served! (and still serve)
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re 263: Thanks. Probably 10 min average then.

re 266/277: The Meteorological Institute of the University of Berlin has a surface pressure archive. I'm looking for it now. I'll be back with it in a few. edit: detailed explanation further down this post.

The MI of the University of Berlin names all high and low pressure systems, this year the highs have male names and the lows female names. Next year the naming practice will be the other way round.
High names for 2011
Low names for 2011

In the drop down menus on top of the lists you find
Tiefdruckgebiete der Jahre (1999 - 2011) meaning Low pressure systems for the years and Hochdruckgebiete meaning high pressure systems.

You can choose one of the years and then you will find all names for the given year.

I chose the lows of 2010 to see how the current storm system was named. I went down to "5. Durchlauf" meaning 5. round. There I can click on the link next to the name Carmen to get to the surface pressure chart for November 9. Carmen was named on November 9 when she appeared far out in the Atlantic.

The provided links only show the days when a new system was named. But there is a trick how to view all days.

By exchanging the date in the last part of the link ".../Analyse_20101109.gif" you can also view November 10 and 11 or 8. Just replace the 09 with the day you want.

I hope the explanation was useful for you, sforzando.
Member Since: August 20, 2007 Posts: 12 Comments: 639
280. Interesting, given this says La Nina well into July.


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Quoting scott39:
We will have one more TC show before 2010 season is over.

And unfortuneatly for me, it's going to brew souuth of Cuba and possibly right over or near Cayman.
Member Since: October 28, 2010 Posts: 0 Comments: 65
280. Skyepony (Mod)
Quoting TropicalAnalystwx13:


La Nina is expected...


I have to disagree.. across the board 2/3rds the models have Neutral or warmer. (click pic to make bigger)


Looking beyond the models a moment.. The end is in sight...clouds have returned to the mid & high latitudes. This should give us a much stronger Polar vortex this winter than we saw last..kicking up some K-waves & slackening the Pacific trade winds causing the collapse of La Nina. Expecting a Dec-Jan peak, near -2, followed by neutral conditions around April-may. After that depends on how strong a polar vortex gets going this winter. If it's strong & mostly undisrupted we may trip into weak el nino conditions around July. If it is weaker & troubled, La Nina would be slower to go & we'd probably see the warm side of neutral for 'cane season next year. The extreme upwelling from this strong La Nina should really feed the vortex clouds & moisture but the extreme Arctic melt makes the vortex less stable.. Dynamical models concur..
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Florida from the ISS



Posted on November 2, 2010
by Astro_Wheels


http://twitpic.com/3338m8
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Quoting KerryInNOLA:
No oil in them. Gulf seafood is the safest in the world because it has been tested so heavily. And it tastes great. My favorite is stuffed baked flounder.The flounder is tender and sweet and the lump crabmeat with shrimp on top is fantastic. With a side of cajun potato salad and a root beer, you are in heaven. And don't forget the garlic french bread.
Now I am starving....Thanx
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Start here I guess...? Link

From 20 years observation,or as the good Doc would say 'in all of recorded history'), the harder the hurricane season, the harder our autumn/winter storms have been. We've had 3 storms/big rain events in 8 days.

My observations are pretty much from the 'higher activity' period we've been experiencing lately since the 90's so any 'conclusions' from that might be conjecture.

Serious European storms from the past here Link

NHC provide much more data more easily on historic years and could be correlated against the data in the link.

There is a strange reluctance to name oncoming storms in Europe. Probably because Peter, Pierre, Pedro, Pietro etc don't give a real clue as to their final landfall until 24/48 hrs beforehand and we wouldn't want to offend our neighbours with a foreign sounding named storm hitting them!

This is chiefly why the 'Union States' got annoyed when Hurricane Earl formed....
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We will have one more TC show before 2010 season is over.
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TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
700 PM EST THU NOV 11 2010
FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER AVILA

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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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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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