Is the Atlantic hurricane season getting longer?

By: Dr. Jeff Masters , 6:34 PM GMT on December 16, 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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257. GBlet
Anybody up for some freezing fog or drizzle, come on now there's plenty to go around!
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165. GBlet 1:49 PM PST on December 17, 2008

Did anyone catch Sci Fi last night? Some scientist believe that the crystal skulls contain the info to stop the damage that we have done to the planet.


um...that was the last "Indiana Jones" movie....you sure you weren't watching HBO last night?


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Quoting hydrus:
TAMPA SPIN-I like your blog,alot of cool satellite loops and earthquake info.I Wanted to leave a comment,but could not find where to type it.


At the bottom where it says comments...
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251. HadesGodWyvern (Mod)
Darwin Tropical Cyclone Warning Center
Tropical Cyclone Advice Number SEVEN
TROPICAL CYCLONE BILLY
11:00 PM ACST December 18 2008
=====================================

At 9:30 pm Australia CST, Tropical Cyclone Billy, Category One [993 hPa] located at 14.5S 128.8E or 85 kms west-southwest of Port Keats and 130 kms northeast of Wyndham has 10 minute sustained winds of 40 knots with gusts of 55 knots. The cyclone is reported moving southeast at 4 knots and is expected to slow and begin moving towards the south or southwest later.

Tropical Cyclone Billy is expected to cross the coast between Wyndham and the NT/WA border during Friday.

GALES with gusts to 120 kilometres per hour are expected to develop on the coast between Kalumburu and Port Keats on Friday morning and may extend further inland into the east Kimberley region later on Friday or early Saturday. Abnormally high tides could cause minor flooding at the coast between Wyndham and Port Keats during Friday.

Widespread heavy rainfall is likely over the southern Darwin-Daly district, the northern Victoria River district and northern parts of the Kimberley over the next 3 days. Significant stream rises and local flooding are expected in these areas on Friday, extending westwards to the north Kimberley over the weekend.

Tropical Cyclone Warnings/Watches
===================================
A Cyclone WARNING has been declared for coastal and island communities from Kalumburu in Western Australia to Port Keats in the Northern Territory.

Tropical Cyclone Technical Bulletin (1200z 18DEC)
---------------------------------

Forecast and Intensity
======================
12 HRS: 14.7S 128.8E - 45 knots (CAT 1)
24 HRS: 15.0S 128.5E - 40 knots (CAT 1)
48 HRS: 15.4S 126.5E - 30 knots (Tropical Low)
72 HRS: 17.2S 123.6E - 30 knots (Tropical Low)

Additional Information
======================
The tropical low has intensified rapidly during the day, with well defined spiral banding evident on Wyndham radar and has been named Tropical Cyclone 'Billy'. The system continued to track slowly towards the southeast, but has recently moved in a series of loops while intensifying. Dvorak analysis at 1200 UTC based on a shear pattern with a radar-derived LLCC on the edge of an area of
deep cold cloud.

FT based on DT=3.0, MET=2.5, PAT=3.0. The cyclone is expected to continue intensifying in a favourable low shear environment despite close proximity to the coast. It is forecast to turn slowly towards the southwest or west during the next 12-24 hours under the influence of a strengthening mid-level ridge to the southwest and move inland over the eastern Kimberley region.
Member Since: May 24, 2006 Posts: 52 Comments: 47000
TAMPA SPIN-I like your blog,alot of cool satellite loops and earthquake info.I Wanted to leave a comment,but could not find where to type it.
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Tampaspin -- left a song on your blog.... geeze, looks like the lake of Mexico... not complaining though.... I need the HOT SUN more then waves.... least for a while
Member Since: July 18, 2007 Posts: 30 Comments: 26536
Quoting MichaelSTL:


That assumes that the upper atmosphere actually does warm as fast as the lower atmosphere, as observations show that the uppermost layers are actually cooling (this is also predicted if greenhouse gasses are actually the cause of global warming; for example, increased solar radiation would cause all layers to warm with more warming higher up). You can check that out here; the following shows the latest daily readings (though daily readings aren't really meaningful), compared to the same day last year (the year overall is fairly similar though):

900 mb: 0.36 degrees F warmer
600 mb: 0.11 degrees F warmer
400 mb: 0.11 degrees F cooler
250 mb: 0.18 degrees F cooler
150 mb: 0.30 degrees F cooler
90 mb: 0.44 degrees F cooler

(it also shows higher levels, though the stratosphere isn't relevant here)

From this, it appears that below 500 mb warming is occurring and above 500 mb cooling (this has also been fairly consistent since I came across the site a few months ago).


This data looks messed up on that link. How can 1998 be colder than now? The El Nino of 1998 was the warmest on record.
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Quoting theshepherd:
Good for you Tampa. Look forward to the finished product.
How about Drummer Boy?
Uh, any cheerleaders need private lessons???


LOL......
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Quoting TampaSpin:
Morning everyone......thinking of having a little fun.......i own a remix program on my computer.....and think i will try to put to together a very long mix of Christmas fun mix that we can play on Christmas eve for those that use their computer for such. If anyone has any request let me know. I do almost anything with this remix program. The wife makes me help her with the Cheerleading dance mixes that she produces.....LOL
Good for you Tampa. Look forward to the finished product.
How about Drummer Boy?
Uh, any cheerleaders need private lessons???
Member Since: September 11, 2008 Posts: 9 Comments: 10167
243. JRRP
Quoting BahaHurican:
Wow! On the Caribbean Sea??? It was warmer here at that time this morning, more like 70. What's the weather like, clear or cloudy?

At this moment is totally clear and breezy
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Quoting conchygirl:
How nice Tampa. I'll send you my request via wumail.


That would be great.....please let me know the song and whom you want that sings it....I will try to produce about 30 songs on one hit if i can and have enough time....LOL
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Quoting TampaSpin:
Morning everyone......thinking of having a little fun.......i own a remix program on my computer.....and think i will try to put to together a very long mix of Christmas fun mix that we can play on Christmas eve for those that use their computer for such. If anyone has any request let me know. I do almost anything with this remix program. The wife makes me help her with the Cheerleading dance mixes that she produces.....LOL
How nice Tampa. I'll send you my request via wumail.
Member Since: June 11, 2008 Posts: 24 Comments: 5910
Morning everyone......thinking of having a little fun.......i own a remix program on my computer.....and think i will try to put to together a very long mix of Christmas fun mix that we can play on Christmas eve for those that use their computer for such. If anyone has any request let me know. I do almost anything with this remix program. The wife makes me help her with the Cheerleading dance mixes that she produces.....LOL
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Quoting JRRP:
good mornging!!!!
the weather in Santo Domingo feels like 62 (17)
That is cool!!!!!!!!!!!!!!!!!!!!!!
Wow! On the Caribbean Sea??? It was warmer here at that time this morning, more like 70. What's the weather like, clear or cloudy?
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Quoting HadesGodWyvern:
Wait. Isn't this the one that they were saying had poor prospects for even getting a name? The conditions must not have deteriorated as much / quickly as they expected they would. Cinda's looking pretty healthy.
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Freezing weather in the Northern States, while those of us in SWFL enjoying the 80's (well maybe not the horses) It's good to be GULFSTER, although if you are looking for waves.... fill the gas tank & go to where the sun rises. Flat on the Gulf, but the East Coast has some lively action........Gulf of Mexico a chilly 62 degrees........wanna be in Trinidad -- where the rum flows freely and wetsuits are an anomaly
Member Since: July 18, 2007 Posts: 30 Comments: 26536
235. JRRP
good mornging!!!!
the weather in Santo Domingo feels like 62 (17)
That is cool!!!!!!!!!!!!!!!!!!!!!!
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Morning

preping for the storm here

Let It Snow
Let It Snow
Let It Snow
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Good Morning All
Wilmington is 58 and partly cloudy
Forecast is sunny and 65!!!
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Good Morning -- lots of interesting reading already!!! I canceled the morning paper about a month ago.... better read in here
Member Since: July 18, 2007 Posts: 30 Comments: 26536
Wyndham RADAR
our local-radar composite
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Quoting HadesGodWyvern:


30 knots 1000 MB

hmm will JTWC issue a TCFA in time before BOM names it "Billy", LOL


LOL, don't worry, next year the Atlantic will have "Bill" according to the list.
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Quoting KoritheMan:
Nice banding in association with Cinda. IIRC, this wasn't forecast to significantly intensify with the initial advisories. Interesting.


We all know the feeling after going through the 2008 and 2007 Hurricane seasons. System's out of the blue rapidly intensifying. I still will never forget Dean or Ike..
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there are those at the college that would like to see Dr, Gray gone.They believe his way of predicting huricane activity is long sence past.
The fact is that Dr. Gray does not subscrible to the Global Warming theory and that presents a wall for those that would like it propagated to be hurtled.
That being said and knowing this /: I would be sceptical as to the forecast they stamp with Dr. Grays appoval.
It will most certainly be scaled to more then what it would be if the Globalist wasnt present.
The next decade i would in my ipinion be sceptical of anythingyou here in regards to global warming or as it is refered to now as climate change.
These people arent interested in the science .They have an adjenda and that my friends is a fact.scientist are being pushed in directions they would not persue other wise because of the politics of the time.
don't think this is a new thing ; It has went on for hundreds of years. The bad thing about it in a time of the greatest tech era of the ages is here ;yet it still goes on.
What a shame it is !True Science will have to be done on low budget personal wage of the scientist will have to be used to conduct even unbiased science.
follow the money and you will find the villon as always . Just think of the damage that will be done in the name of science for political ends. i don't post much here but thought sence there is a lul in activity ;this would be a good time to introduce the activities as some as fraudulent as they are.
Hope you all take it all with a grain of salt and keep in mind that some science inst science at all.
have a good day last post see ya .
dew
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227. HadesGodWyvern (Mod)


30 knots 1000 MB

hmm will JTWC issue a TCFA in time before BOM names it "Billy", LOL
Member Since: May 24, 2006 Posts: 52 Comments: 47000
226. HadesGodWyvern (Mod)
Tropical Cyclone Technical Bulletin (0600z 18DEC)
---------------------------------

TROPICAL LOW

Forecast and Intensity
======================
12 HRS: 14.4S 128.8E - 40 knots (CAT 1)
24 HRS: 14.6S 128.7E - 40 knots (CAT 1)
48 HRS: 14.7S 127.3E - 25 knots (Tropical Low)
72 HRS: 16.1S 124.7E - 25 knots (Tropical Low)

Additional Information
======================
The low has undergone significant development during the day, whilst tracking steadily to the southeast. Dvorak analysis at 06Z has DT2.5 [0.55 curved band wrap], MET=PT=FT=2.5.

The system is located under the upper ridge, so vertical shear is not a problem. Standard development rate has the low reaching TC intensity early on Friday, just prior to crossing the coast.

Member Since: May 24, 2006 Posts: 52 Comments: 47000
while you guys look at current tech and statistics to see what the next decade will bring i will be looking at the 12th and 13th century for the answer to that puzzle.
These little statistical things we do now may come in handy three hundred years from now.
Fact is the patterns on earth are far more intwind in time then some think .the big huricane season of 2005 was a pivital point inwhitch people in the future will say.
that was the turning point and i remember it .we are in a cooling period !!!!!
This period will last anywhere from 35 to 70 years ,that is if it doesnt last 300 hundred years.
Drought is the worst of it all . cooling periods are laiden with drought.that will be the greatest misery in it . remeber the great potato famine.
our cycles and patterns are not i repeat not the cause of man!!!!!!!!!!!!!!!!!
the patterns on earth are a direct result of our sun and the patterns in our planets and moon. the earth is growing in size .that can be proved by looking at the land masses and how they spread from each other .
science isnt and exact science if you know what i mean . he he just don't think that anything you here in regards to hurricane activity is rock solid .
Fact is the earth was as close to the Sun as it has b een in 40,000 years it would if you use commen sence that the Earth would be warmer. Note that heat rises and brings into it cold so keep that in mind too .
Another words everything I have said here has just as much likely hood of happening as any other . keep the faith
dew
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224. HadesGodWyvern (Mod)
Tropical Cyclone Warning Center Darwin
Tropcial Cyclone Advice Number FIVE
TROPICAL LOW (02U)
5:00 pm ACST December 18 2008
===============================

At 3:30 pm Australia CST, a Tropical Low [997 hPa] located at 14.1S 128.6E or 100 kms west of Port Keats and 215 kms east of Kalumburu has 10 minute sustained winds of 30 knots with gusts of 45 knots. The low is moving southeast at 5 knots.

There is the possibility of a tropical cyclone developing in the Joseph Bonaparte Gulf tonight or early on Friday. GALES may develop between Port Keats and Kalumburu overnight or early on Friday.

Widespread heavy rainfall is likely over the southern Darwin-Daly district, the northern Victoria River district, and northern parts of the Kimberley over the next 3 days. Significant stream rises and local flooding are expected in these areas on Friday, extending westwards to the north Kimberley over the weekend.

Tropical Cyclone Warnings/Watches
===================================
A Cyclone WARNING has been declared for coastal and island communities from Kalumburu in Western Australia to Port Keats in the Northern Territory.

The Cyclone WATCH from Cockatoo Island to Kalumburu in WA has been cancelled.

The next advice will be issued by 11:00 pm ACST
Member Since: May 24, 2006 Posts: 52 Comments: 47000
223. HadesGodWyvern (Mod)
ya surprising storm that was suppose to only remain a tropical depression two days ago.
Member Since: May 24, 2006 Posts: 52 Comments: 47000
Nice banding in association with Cinda. IIRC, this wasn't forecast to significantly intensify with the initial advisories. Interesting.
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221. HadesGodWyvern (Mod)
Member Since: May 24, 2006 Posts: 52 Comments: 47000
220. HadesGodWyvern (Mod)
Mauritius Meteorological Services
Tropical Cyclone Warning Number TEN
FORTE TEMPETE TROPICALE CINDA 04-20082009
10:00 AM Reunion December 18 2008
======================================

At 6:00 AM UTC, Severe Tropical Storm Cinda (985 hPa) located at 12.2S 66.8E has 10 minute sustained winds of 50 knots with gust of 70 knots. The storm is reported as moving south at 5 knots.

Dvorak Intensity: T3.5

Storm Force Winds
===================
20 NM radius from the center

Gale-Force Winds
====================
30 NM radius from the center extending up to 40 NM in southern semi-circle

Near-Gale Force Winds
=====================
80 NM in the southern semi-circle

Forecast and Intensity
=========================
12 HRS: 13.2S 66.3E - 50 knots (Forte Tempête Tropicale)
24 HRS: 14.0S 65.4E - 40 knots (Tempête Tropicale Modereé)
48 HRS: 14.6S 63.0E - 30 knots (DEPRESSION TROPICALE)

Additional Information
======================
Satellite imagery analysis leads to T=CI T3.5 however 85 ghz microwave and infrared/visible imagery are much more impressive than 37 ghz microwave imagery. 85 ghz imagery (F17/0052z, F15/0156z, F16/0325z) actually displays a rather well defined eye. but on the 37 ghz, this eye is eroded on the northern edge. Moreover these imagerires show a tilt between the low level and the upper level center. This shows the system is undergoing a northerly constraint. The environment remains however slightly favorable. Located beneath the western periphery of the upper level ridge, the system benefits from still rather weak vertical wind shear, while the upper outflow is restricted to a moderately potent poleward channel (ahead of an upper trough to the west). This environment is still forecast to become less and less favorable with the strengthening of northern to northwestern winds and the loss of the upper level ridge. About the forecast track, it seem that current steering flow are from the mid-level (700/500 HPA) - where they are somewha weak as the system is located on the western edge of a mid level ridge. As the system should gradually weaken, it should be steered by a more low level steering flow and then track west-southwestwards.
Member Since: May 24, 2006 Posts: 52 Comments: 47000
Lurk-n in the warm sector (for now). Let's watch it out there in the fog.
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SNOWFALL WARNING: Greater Victoria Issued at 6:53 PM PST WEDNESDAY 17 DECEMBER 2008

FURTHER SNOWFALL ACCUMULATIONS UP TO 15 CM OVER MAINLY VICTORIA AND SOUTHERN SECTIONS OF EAST VANCOUVER ISLAND WITH ADDITIONAL ACCUMULATIONS NEAR 5 CM OVER MUCH OF THE INNER SOUTH COAST. THIS IS A WARNING THAT SIGNIFICANT SNOWFALL IS EXPECTED OR OCCURRING IN THESE REGIONS. MONITOR WEATHER CONDITIONS..LISTEN FOR UPDATED STATEMENTS.
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Quoting surfmom:
sooo ahhh Orca... what you bring back? Tequila, Orcas....... a good tan?


The tan I got :)
Pictures I have...
I also Have SNOW... WTF??
Mother nature was very rude when we got back here.. from Tequila to a snow shovel :(



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Thanks Micheal, that's all I could find too. I guess you're right about post analysis, I haven't seen anything updated since Sept. either. Wiki still says 202 missing and there's no way that's true. I'm sure most of those people were either displaced or some perhaps dead, but I'm sure most are since accounted for. Thanks again
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MichealSTL, do you suppose you could answer my question, that is if you're still here?
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209. DDR
looks like the us desert sw is getting some rain
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Quoting surfmom:
sooo ahhh Orca... what you bring back? Tequila, Orcas....... a good tan?


Hey surfmom!!
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No Orca yet - probably hasn't had time to turn the computer on!

Still hanging Christmas lights - and still sweating while we are doing it. Don't know whether I prefer the warm temps or the ability to stay cool for a while.

Our daughter in Maine finally got power back last night. We were threatening to fly up and get the baby, poor guy doesn't know what to do with only cold water.
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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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