Is the Atlantic hurricane season getting longer?

By: Dr. Jeff Masters , 06:34 PM GMT del 16 Dicembre 2008

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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. 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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Doc foretold the future 2 years ago!
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.

Member Since: Luglio 8, 2005 Posts: 259 Comments: 23015
Click to enlarge.....



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Oh, Tampa. I know it really isn't funny but I am laughing so hard now at the thought of the cat doing that ~
Member Since: Giugno 11, 2008 Posts: 24 Comments: 5910
Quoting pottery:
Good day, to all.
Still raining here (Trinidad), including a major cloud-burst over the city of Port-of-Spain last evening. In several of the valleys around the city, roads were washed out, homes damaged, bridges overtopped.
Looking at the sat-loops, more to come as well.
Going to be a wet weekend and beyond, from the looks of things.
Stay safe Pottery. Have you visited the training camp. LOL
Member Since: Giugno 11, 2008 Posts: 24 Comments: 5910
Quoting conchygirl:
Morning all! Tampa - how's the Christmas music coming along?


Had it almost done and lost it all when the i walked away the darn cat jumped up on the desk and hit the keyboard and locked my computer up....can you believe it.....LOL i will try again....i will get it done by Tuesday...LOL
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Click to enlarge......
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Good day, to all.
Still raining here (Trinidad), including a major cloud-burst over the city of Port-of-Spain last evening. In several of the valleys around the city, roads were washed out, homes damaged, bridges overtopped.
Looking at the sat-loops, more to come as well.
Going to be a wet weekend and beyond, from the looks of things.
Member Since: Ottobre 24, 2005 Posts: 0 Comments: 23094
Morning all! Tampa - how's the Christmas music coming along?
Member Since: Giugno 11, 2008 Posts: 24 Comments: 5910
Earthquake in North Atlantic......very unsual spot....NO Tsunami was expected..

Magnitude 5.9 - NORTHERN MID-ATLANTIC RIDGE
2008 December 19 08:31:52 UTC
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Wow,got up this morning and everything is covered in ice. Went to my office and now it is lightning and thundering.
Metar for ksbn says 11 knots from ESE, broken clouds at 700 ft, 32F, 29F dew point.

Everything is closed and the road in front of my house is not carrying much traffic.

One of the dangers of this kind of storm is getting iced into your house. Both doors here were difficult to open. A little more ice and the door would have had to have been broken to exit the building.

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347. ayi
From the Wyndham radar it appears TC Billy is finally starting to cross the coast.
http://mirror.bom.gov.au/products/IDR072.loop.shtml
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Quoting NEwxguy:
It took a while for winter to arrive here in the northeast,but its here!!!


Um, winter doesn't start for another day or 3.
Member Since: Ottobre 6, 2005 Posts: 0 Comments: 90
Storm that walloped Southwest targets the East


(CNN) -- After blanketing parts of the Southwest with snow, a major winter storm headed eastward late Thursday with new strength, the National Weather Service said.

"This is essentially the reincarnation of the same storm that brought the heavy snow to parts of California, southern Nevada and northern Arizona," Steve Corfidi, lead forecaster with the weather service's Storm Prediction Center in Norman, Oklahoma, told CNNRadio.

Corfidi said the storm is expected to maintain intensity into Saturday, continuing eastward and "spreading a swath of very heavy snow and freezing rain all the way into Pennsylvania and New York."

Storm watches and warnings extended from the central Plains to the mid- and north-Atlantic coast, he said.

"There could easily be up to a foot of snow over parts of Illinois, northern Indiana, perhaps into parts of Michigan and southern Wisconsin, eastward into parts of New York and Pennsylvania," Corfidi said.

The system should move quickly, Corfidi said. It was not shaping up as an extraordinary winter event, he said.

"It is December, and winter storms certainly raise their ugly heads this time of year," Corfidi said.




From Accuweather:


Storms Target Major Cities Coast to Coast

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The fast-moving storm that dumped over 3 inches of snow on Wednesday in Las Vegas will slam a number of major cities east of the Rockies today, including Chicago, New York and Boston, creating the potential for widespread travel problems.

Expert Senior Meteorologist Bernie Rayno says that the week before Christmas could be the stormiest week of the winter of 2008 - 2009.

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The near-constant parade of storms that began last week will continue to spread a nasty mix of rain, ice and snow across the country right up until Christmas Eve.

The recent storm in the Southwest and a new storm in the Northwest have dropped phenomenal snowfall in some areas. Dry, desert areas that typically see little or no snow through the entire winter have been buried by heavy snow from these single storms.

Snow is being measured in feet over interior Washington, while the ground was blanketed with snow in southern Nevada.

Three storms over the next week will move from the West Coast across the central Plains into the Midwest and the Northeast. Each will produce substantial snow and heavy rain sandwiched around a dangerous band of icy precipitation.


Photobucket

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Morning
ILM has FOG with a vis of 1/2 mile
58F
Forecast is for 72F and partly cloudy
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Anybody awake at this ungodly hour?

5.5 offa the coast of Chile. Near Valpairiso (sp?) where we were watching a volcano last year about this time, I believe.

tsunami warnings anyone? thanks
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CNN Meteorologist Chad Myers had never bought into the notion that man can alter the climate and the Vegas snowstorm didn’t impact his opinion. Myers, an American Meteorological Society certified meteorologist, explained on CNN’s Dec. 18 “Lou Dobbs Tonight” that the whole idea is arrogant and mankind was in danger of dying from other natural events more so than global warming.



“You know, to think that we could affect weather all that much is pretty arrogant,” Myers said. “Mother Nature is so big, the world is so big, the oceans are so big – I think we’re going to die from a lack of fresh water or we’re going to die from ocean acidification before we die from global warming, for sure.”

http://businessandmedia.org/articles/2008/20081218205953.aspx
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341. HadesGodWyvern (Mod)
Darwin Tropical Cyclone Warning Center
Tropical Cyclone Advice Number THIRTEEN
TROPICAL CYCLONE BILLY
5:21 PM ACST December 18 2008
=====================================

At 3:00 pm WDT, Tropical Cyclone Billy, Category Two [983 hPa] located at 14.5S 128.7E or 125 kms north-northeast of Wyndham and 95 kms west-southwest of Port Keats has 10 minute sustained winds of 50 knots with gusts of 70 knots. The cyclone is reported as moving southwest slowly.

Gale-Force Winds
===============
40 NM from the center

The cyclone may intensify further before landfall.

Tropical Cyclone Billy is expected to cross the coast near Wyndham tonight.

Tropical Cyclone Watches/Warnings
=================================
A Cyclone WARNING is now current for coastal areas from Mitchell Plateau in Western Australia to Port Keats in the Northern Territory.

A Cyclone WATCH has been declared for coastal areas from Mitchell Plateau to Cockatoo Island.

Tropical Cyclone Technical Bulletin
===================================
12 HRS: 14.8S 128.4E - 50 knots (CAT 2)
24 HRS: 15.0S 127.6E - 35 knots (CAT 1)
48 HRS: 15.5S 125.9E - 30 knots (TROPICAL LOW)

REMARKS:
Tropical Cyclone 'Billy' is moving slowly west southwest. Dvorak analysis at 0600 UTC based on central dense overcast pattern with radar-derived LLCC centred under area of deep cold cloud.

FT based on DT=3.5 MET=3.5. It is expected to
continue moving towards the southwest under the influence of a mid-level ridge to the southwest.
Member Since: Maggio 24, 2006 Posts: 48 Comments: 43701
well, ns sherlock, given the phase of the PDO...

looks to me like the western Pacific would warm as a result...

Oscillation rules as the Pacific Ocean cools
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338. ayi
Quoting P451:


Mostly a rainmaker I suspect? Little breezy no doubt.


Interesting how Kalumburu has only had about 8mm rain in the past 50 odd hours but Wadeye has had about 330mm in the same time. The rainfall is very one sided about TC Billy's COC.
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Quoting MidWtornado:
Hey guys, not a professional, but I am monitoring the redar. Are we in for a storm in Chicago as big as predicted? Not much on radar. Amature...


Um... http://www.wunderground.com/radar/mixedcomposite.asp?region=a4&size=2x&type=loop

Mind you, this is 1-3 in. per hour you're looking at here. So yes, you're gonna get nailed.

Member Since: Ottobre 15, 2008 Posts: 11 Comments: 2305
Hey guys, not a professional, but I am monitoring the redar. Are we in for a storm in Chicago as big as predicted? Not much on radar. Amature...
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Quoting BahaHurican:
Again we are hampered by lack of reliable records. The S Atlantic may go through cycles of formation that act on a different scale from the NATL and other basins. How far back do our storm databases go for that area? Are they reliable enough in reporting the features of the storms encountered to enable us to discern an existing pattern?

Sometimes an anomaly is only an anomaly until the pattern it fits is discovered. . .


Exactly why I said recorded storms, not storms.
Member Since: Ottobre 15, 2008 Posts: 11 Comments: 2305
A little Christmas ditty for the evening...

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Quoting AussieStorm:
TC Billy is currently 100km's NNE of Wyndham and about 19km from landfall. Looking really nice on RADAR Link
Cheers AussieStorm
Gotta love the new BOM toys available online. When I first went to their website, they didn't even let u see the radars, much less with all the bells and whistles . . . lol

That COC is pretty well defined. Looks like it might stay intact long enough to cross the peninsula.
Member Since: Ottobre 25, 2005 Posts: 19 Comments: 20742
Link
un tormenta tropical nuevo en el Ociano Pacifico?
Member Since: Marzo 29, 2008 Posts: 0 Comments: 2338
Quoting GeoffreyWPB:
lol...latest Senate vote between Coleman and Franken...Coleman up by 2! That was after millions of votes! Just goes to show you..every vote counts!!!
Lol there are likely two Coleman voters out there who are glad they voted, and three Franken supporters who are mad they didn't. . . lol
Member Since: Ottobre 25, 2005 Posts: 19 Comments: 20742
North...yea....we had a 3.6 just North of Charleston....no biggie....
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there was a blogger on here a few years ago who traveled the coastline documenting Katrina's aftermath... could someone please link me if you remember...thx
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Quoting MichaelSTL:


Actually, that isn't true; if greenhouse gasses are the cause of the observed warming (models also predict this), the surface and lowest part of the troposphere should warm but further up warming is less and eventually switches over to cooling. The site I linked to earlier says that:


During global warming, the atmosphere near the surface is supposed to warm at least as fast as the surface warms, while the upper layers are supposed to cool much faster than the surface warms.


Weather Underground also as a page on that in their climate section (some links to more technical stuff as well); ozone loss also causes cooling but only where the ozone layer is, cooling is also occurring higher up; the following in particular is startling (a very good thing the surface is only warming at 1/100th of this rate!):


Even greater cooling of 17 C per decade has been observed high in the ionosphere, at 350 km altitude. This has affected the orbits of orbiting satellites, due to decreased drag, since the upper atmosphere has shrunk and moved closer to the surface (Lastovicka et al., 2006). The density of the air has declined 2-3% per decade the past 30 years at 350 km altitude. So, in a sense, the sky IS falling!


My point exactly: global warming is a VERY complicated process. This year, Discover magazine reported enormous chunks of ice falling from a clear sky as a result of climate change! Also, since the extra sky pressing onto the troposphere would thus increase its pressure, and thus its heat content, would this count as a positive feedback mechanism?
Member Since: Agosto 30, 2008 Posts: 8 Comments: 2834
TC Billy is currently 100km's NNE of Wyndham and about 19km from landfall. Looking really nice on RADAR Link
Cheers AussieStorm
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Was there a earthquake in S.C Tuesday? I slept most of the day, did I miss something?
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Quoting BahaHurican:
Hmmm. What do u think are the chances of the low hanging about long enough to exit near Kuri Bay?

Cyclone Billy threatens Kimberley coast Link
Cyclone Billy brewing to category 2
Link
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lol...latest Senate vote between Coleman and Franken...Coleman up by 2! That was after millions of votes! Just goes to show you..every vote counts!!!
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Seasonal and Long-Term Variations of Particle Fluxes Induced by ...
The high particle fluxes in December-May are attributed to the strong NE trade wind caused by southward shift of the Intertropical Convergence Zone (ITCZ). ...Link

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Atmospheric Circulation



Microscale

* Size: meters
* Time: seconds

Mesoscale

* Size: kilometers
* Time: minutes to hours

Macroscale
Synoptic

* Size: 100s to 1000s kilometers
* Time: days

Global (planetary)

* Size: Global!
* Time: Days to weeks

Macroscale Circulation Link

To begin, imagine the earth as a non-rotating sphere with uniform smooth surface characteristics.
Assume that the sun heats the equatorial regions much more than the polar regions.
In response to this, two huge convection cells develop.
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Found an interesting comment here about S. ATL cyclones, in which the writer remarks "A broad convergence zone like this needs to reach about 5 degrees of latitude away from the equator in order for the Coriolis Force to have sufficient intensity to organize a full-fledged tropical cyclone, and the Atlantic ITCZ almost never shifts that far south. . ."

I'm thinking about how far south we've been seeing the ITCZ loop some years and wondering if shifts in global SST patterns (I'm thinking about naturally occurring longer range shifts, like those related to NAO / PDO e.g.) could result in a longer "season" for S Atlantic / near Equator cyclones (like Vaimei e.g.). Maybe the S Atlantic "tropical season" has a 10 or 15 year recurrance wave . . . I'm also curious how effective sat. coverage of the S. Atlantic was in say, the 60s, when compared with the NAO. I can't say I'd see the scientists of the time spending much time/energy peering at the SAO when the NAO is where the US landing storms are most likely to form . . .
Member Since: Ottobre 25, 2005 Posts: 19 Comments: 20742
318. Skyepony (Mod)
It would be interesting to see more on the minimum temp for 'cane formation rising. It seems we've had a few freak storms lately that formed in waters cooler than the current minimum temps. I wish I had a little time to look at the stats on that.
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The east is expected to switch to a progressive pattern with a deep mean trough embedded while a ridge builds in the west next week. Looks like a white Christmas favors more those to the east.
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316. Skyepony (Mod)
I can't get your link to open either. Good stuff though. Dr Masters has done a few blogs on it.
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315. Skyepony (Mod)
Michael~ Back in the early '90s Chem class for science majors...we expected the stratosphere to become exteme end of cold as we know it but widely in the community at large it wasn't really known or expected til there became no doubt. I linked current data that totally supports what you said. It shows the upper ends of our atmosphere like 3rd coldest last month.

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Quoting HadesGodWyvern:


Billy is expected to become a Category Two cyclone (between 50-65 knots) before landfall north of Wyndham.
Hmmm. What do u think are the chances of the low hanging about long enough to exit near Kuri Bay?
Member Since: Ottobre 25, 2005 Posts: 19 Comments: 20742
Quoting hurristat:


While there have been three over a period of two years (04-06), that does not qualify the Southern Atlantic as a Cyclone producing region... those storms were anomalies. Outside of that there have been two recorded storms... we still have a long way to go b4 we start talking about the Southern Atlantic Cyclone season.
Again we are hampered by lack of reliable records. The S Atlantic may go through cycles of formation that act on a different scale from the NATL and other basins. How far back do our storm databases go for that area? Are they reliable enough in reporting the features of the storms encountered to enable us to discern an existing pattern?

Sometimes an anomaly is only an anomaly until the pattern it fits is discovered. . .
Member Since: Ottobre 25, 2005 Posts: 19 Comments: 20742
312. HadesGodWyvern (Mod)


Billy is expected to become a Category Two cyclone (between 50-65 knots) before landfall north of Wyndham.
Member Since: Maggio 24, 2006 Posts: 48 Comments: 43701
hurristat I sent you mail.
Member Since: Agosto 30, 2008 Posts: 8 Comments: 2834
309. HadesGodWyvern (Mod)
Darwin Tropical Cyclone Warning Center
Tropical Cyclone Advice Number TEN
TROPICAL CYCLONE BILLY
8:00 AM ACST December 18 2008
=====================================

IMMEDIATE TROPICAL CYCLONE ADVICE

At 6:30 am Australia CST, Tropical Cyclone Billy, Category One [988 hPa] located at 14.5S 128.8E or 130 kms northeast of Wyndham and 85 km west-southwest of Port Keats has 10 minute sustained winds of 45 knots with gust of 65 knots. The cyclone is reported as moving southeast at 1 knot, but is expected to begin moving towards the southwest later.

The cyclone may intensify further before landfall.

Tropical Cyclone Billy is expected to cross the coast between Wyndham and the North Territory/Western Australia border later today.

Tropical Cyclone Warning
========================
A Cyclone WARNING continues for coastal communities from Kalumburu in Western Australia to Port Keats in the Northern Territory.
Member Since: Maggio 24, 2006 Posts: 48 Comments: 43701
It took a while for winter to arrive here in the northeast,but its here!!!
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Quoting biff4ugo:
Dr. Masters may want to specify that this is lenghting is only true for the "North" Atlantic.
The "South" Atlantic seems to be a newly developing bed for hurricanes and there may well be more of them heading toward Brasil and curving south.


While there have been three over a period of two years (04-06), that does not qualify the Southern Atlantic as a Cyclone producing region... those storms were anomalies. Outside of that there have been two recorded storms... we still have a long way to go b4 we start talking about the Southern Atlantic Cyclone season.
Member Since: Ottobre 15, 2008 Posts: 11 Comments: 2305

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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.