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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622. Neapolitan
8:35 PM GMT on November 12, 2010
NEW BLOG
Member Since: November 8, 2009 Posts: 4 Comments: 13803
621. outlookchkr
8:09 PM GMT on November 12, 2010
Quoting utilaeastwind:
It appears that there is some mid/low level circulation at 11.2 N 74.1W.

Any thoughts?
Might be the Invest?
Member Since: October 28, 2010 Posts: 0 Comments: 65
619. utilaeastwind
8:01 PM GMT on November 12, 2010
It appears that there is some mid/low level circulation at 11.2 N 74.1W.

Any thoughts?
Member Since: October 12, 2007 Posts: 0 Comments: 192
618. TampaTom
7:57 PM GMT on November 12, 2010
Quoting AnthonyJKenn:
Ahhh...wasn't Wilma October 2005??

Unless my memory's fading me, the last hurricane to make landfall in US was Ike in 2008.

And...the last major, I believe, was Wilma.

I could be wrong, of course.


Anthony


Yes, I blew the call... my bad...
Member Since: June 20, 2005 Posts: 22 Comments: 1054
617. Orcasystems
7:54 PM GMT on November 12, 2010
Complete Update






TSPIN BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26516
616. AnthonyJKenn
7:52 PM GMT on November 12, 2010
Ahhh...wasn't Wilma October 2005??

Unless my memory's fading me, the last hurricane to make landfall in US was Ike in 2008.

And...the last major, I believe, was Wilma.

I could be wrong, of course.


Anthony
Member Since: September 20, 2005 Posts: 0 Comments: 210
614. outlookchkr
7:52 PM GMT on November 12, 2010
Quoting winter123:

Amazing looking invest. May have a TD by sunday IMO.
Dry air could be a limiting factor.
Member Since: October 28, 2010 Posts: 0 Comments: 65
613. Tazmanian
7:49 PM GMT on November 12, 2010
i wounder if we will make it too the W storm
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
612. flsky
7:49 PM GMT on November 12, 2010
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

That was fun - thanks! I also like seeing the little dog romping around. It's funny how dogs love the snow so much, isn't it.
Member Since: October 24, 2006 Posts: 0 Comments: 2114
611. tornadodude
7:48 PM GMT on November 12, 2010

Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE DULUTH MN
956 AM CST FRI NOV 12 2010

...HEAVY SNOW EXPECTED FOR PORTIONS OF THE NORTHLAND THIS
WEEKEND...

MNZ012-019>021-035>038-WIZ001>004-006>009-130000-
/O.CON.KDLH.WS.A.0003.101113T1800Z-101114T2200Z/
NORTHERN COOK/NORTHERN LAKE-CENTRAL ST. LOUIS-
SOUTHERN LAKE/LAKESHORE-SOUTHERN COOK/LAKESHORE-NORTHERN AITKIN-
SOUTHERN AITKIN-CARLTON/SOUTHERN ST. LOUIS-PINE-DOUGLAS-BAYFIELD-
ASHLAND-IRON-BURNETT-WASHBURN-SAWYER-PRICE-
INCLUDING THE CITIES OF...ISABELLA...HIBBING...TWO HARBORS...
GRAND MARAIS...HILL CITY...AITKIN...DULUTH...CLOQUET...HINCKLEY...
SUPERIOR...WASHBURN...ASHLAND...HURLEY...GRANTSBURG...SPOONER...
HAYWARD...PHILLIPS
956 AM CST FRI NOV 12 2010

...WINTER STORM WATCH REMAINS IN EFFECT FROM SATURDAY AFTERNOON
THROUGH SUNDAY AFTERNOON...

* TIMING AND LOCATION: SNOW...POSSIBLY MIXED WITH RAIN...WILL
SPREAD NORTH OVER WISCONSIN AND EASTERN MINNESOTA SATURDAY
THROUGH SUNDAY.

* SNOW ACCUMULATIONS: SNOWFALL TOTALS OF 8 INCHES OR MORE ARE
EXPECTED ALONG THE SAINT CROIX RIVER VALLEY AND INTERSTATE 35
CORRIDOR...AS WELL AS ALONG THE INLAND PORTIONS OF THE MINNESOTA
ARROWHEAD.

SNOWFALL TOTALS WILL VARY GREATLY ACROSS NORTHERN
WISCONSIN WHERE THE SNOW WILL MIX WITH OR CHANGE TO RAIN AT
TIMES. SNOWFALL TOTALS OF 2 TO 8 INCHES ARE EXPECTED EAST OF
HAYWARD AND HIGHWAY 63 IN NORTHERN WISCONSIN.


LITTLE OR NO SNOW ACCUMULATION WILL BE FOUND ALONG THE SHORES
OF LAKE SUPERIOR...INCLUDING DOWNTOWN DULUTH...SATURDAY AND
SATURDAY NIGHT.

* MAIN IMPACT: THE SNOW WILL BE HEAVY AT TIMES FOR SOME
LOCATIONS...RESULTING IN SNOW AND SLUSH COVERED ROADS AND
REDUCED VISIBILITY. LOCATIONS NEAR LAKE SUPERIOR CAN EXPECT ALL
RAIN SATURDAY...MIXING WITH LIGHT SNOW ON SUNDAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS WINTER STORM WATCH MEANS THERE IS THE POTENTIAL FOR
SIGNIFICANT ACCUMULATION OF SNOW THAT WILL IMPACT TRAVEL AND
COMMERCE. STAY CURRENT WITH THE LATEST WEATHER INFORMATION AND
UPDATES AS THEY BECOME AVAILABLE.

&&

$$

GRANING




Member Since: June 28, 2006 Posts: 25 Comments: 8360
610. TampaTom
7:46 PM GMT on November 12, 2010
Quoting 7544:
wilma was in 2008 ? hmmm



AAAAAK! I messed that one up...

2005 - mea culpa...
Member Since: June 20, 2005 Posts: 22 Comments: 1054
609. tornadodude
7:44 PM GMT on November 12, 2010
Member Since: June 28, 2006 Posts: 25 Comments: 8360
608. tornadodude
7:44 PM GMT on November 12, 2010
Indian Summer

The temperature has reached 70 degrees today (Friday) at the Indianapolis airport, making this the 5th consecutive day with a high temperature of 70 degrees or higher. This has occurred only 3 times after the 7th of November. The last time was in 1971 from November 14-18. The longest stretch of 70 degree weather after the 7th is 6 days. This occurred from November 14-19, 1953. Although the high temperature Saturday is not forecast to get up to 70, if it does we will tie the record. A cold front will move through the area by Saturday night, however, bringing the string of warm days to an end.

Weather records began at Indianapolis in February 1871.

NWS Indy
Member Since: June 28, 2006 Posts: 25 Comments: 8360
607. Drakoen
7:40 PM GMT on November 12, 2010
Quoting nrtiwlnvragn:
UK Met Office claims skill in predicting the number of hurricanes beyond the seasonal time scale.

Hurricane Forecasts Can Be Made Years in Advance
Climate modelers push Atlantic predictions beyond a single season



Will be interesting to see their numbers for the next few years.


Nice Article.

It is also worth noting that the UKMET office forecast for 20 named storms to form this Atlantic hurricane season. If we get Virginie (which appears likely), that would be remarkable verification.
Member Since: October 28, 2006 Posts: 57 Comments: 30833
606. winter123
7:37 PM GMT on November 12, 2010

Amazing looking invest. May have a TD by sunday IMO.
Member Since: July 29, 2006 Posts: 28 Comments: 1802
605. 7544
7:36 PM GMT on November 12, 2010
wilma was in 2008 ? hmmm
Member Since: May 6, 2007 Posts: 0 Comments: 6874
604. Irth
7:34 PM GMT on November 12, 2010
Quoting Jax82:
Interesting you can see two lines of clouds over Texas



I believe that the eastern line of clouds (which produced heavy rains here in the DFW area about an hour and a half ago) was associated with an upper level wind shift ahead of the cold front moving in from the west (second line of clouds).

Imediatly behind the forward line of rain the winds are still steady out of the south, and humidity is high. The temperature is only a few degrees cooler, which I attribute to the rain, and not any actual cold air mass.

Immediatly behind the second line of rain, the wind is out of the north, temperatures are about 20 - 30 degrees cooler (upper 30's and low to mid 40's rather than the low 70's here in North Dallas / Plano, and humidity is high.

Fall has officially arrived to North Texas.
Member Since: July 27, 2010 Posts: 0 Comments: 7
603. Skyepony (Mod)
7:32 PM GMT on November 12, 2010
Quoting Stormchaser2007:
20th storm of the season set to develop. Amazing.



22nd including depressions
Member Since: August 10, 2005 Posts: 226 Comments: 39438
602. weaverwxman
7:28 PM GMT on November 12, 2010
Quoting TampaTom:


Exactly... and, you can say that Florida has not seen a landfalling hurricane since Wilma in October 2008...
THANK GOD
Member Since: November 17, 2009 Posts: 0 Comments: 383
601. DontAnnoyMe
7:28 PM GMT on November 12, 2010
Quoting lilElla:
Sorry but not sure how to link.
Maybe someone can help me with that?


Right above where you type your comments, click the Link box and paste your URL in there.
Member Since: September 21, 2010 Posts: 1 Comments: 3690
600. TampaTom
7:09 PM GMT on November 12, 2010
Quoting PensacolaDoug:
Debateable whether Ike was a major or not. Regardless the statement was "no hurricanes have made landfall on the US since 04-05"...

Just keeping the record straight.


Exactly... and, you can say that Florida has not seen a landfalling hurricane since Wilma in October 2005...
Member Since: June 20, 2005 Posts: 22 Comments: 1054
599. Hurricanes101
6:59 PM GMT on November 12, 2010
Quoting AstroHurricane001:


Neither Gustav nor Ike made landfall as a major hurricane. Both hit as a strong cat. 2 on the Gulf Coast.


they said hurricane, they did not specify major hurricane
Member Since: March 10, 2010 Posts: 1 Comments: 7874
597. Stormchaser2007
6:48 PM GMT on November 12, 2010
20th storm of the season set to develop. Amazing.

Member Since: June 9, 2007 Posts: 4 Comments: 15950
596. nrtiwlnvragn
6:44 PM GMT on November 12, 2010
UK Met Office claims skill in predicting the number of hurricanes beyond the seasonal time scale.

Hurricane Forecasts Can Be Made Years in Advance
Climate modelers push Atlantic predictions beyond a single season



Will be interesting to see their numbers for the next few years.
Member Since: September 23, 2005 Posts: 15 Comments: 11343
595. AstroHurricane001
6:43 PM GMT on November 12, 2010
Quoting Jax82:
I'm guessing the reason its not an Invest yet is because most of the energy is still over land, but is close to emerging over water? Thats what i'm thinking.


It IS an invest now.

Member Since: August 30, 2008 Posts: 8 Comments: 2836
594. PensacolaDoug
6:41 PM GMT on November 12, 2010
Debateable whether Ike was a major or not. Regardless the statement was "no hurricanes have made landfall on the US since 04-05"...

Just keeping the record straight.
Member Since: July 25, 2006 Posts: 0 Comments: 669
593. AstroHurricane001
6:39 PM GMT on November 12, 2010
Quoting TampaTom:


The Weather Network is off base... unless storms such as Gustav and Ike don't count...


Neither Gustav nor Ike made landfall as a major hurricane. Both hit as a strong cat. 2 on the Gulf Coast.
Member Since: August 30, 2008 Posts: 8 Comments: 2836
592. CaicosRetiredSailor
6:38 PM GMT on November 12, 2010
Member Since: July 12, 2007 Posts: 0 Comments: 6069
591. 7544
6:34 PM GMT on November 12, 2010
couple of early models take 94l due north toward cuba waitng for others
Member Since: May 6, 2007 Posts: 0 Comments: 6874
589. PensacolaDoug
6:32 PM GMT on November 12, 2010

The States have not seen a hurricane make landfall since the 2004-2005 season, when seven major hurricanes touched down in America


What about Gustave and Ike?
Member Since: July 25, 2006 Posts: 0 Comments: 669
588. TampaTom
6:22 PM GMT on November 12, 2010
Quoting Orcasystems:


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


The Weather Network is off base... unless storms such as Gustav and Ike don't count...
Member Since: June 20, 2005 Posts: 22 Comments: 1054
587. JRRP
6:20 PM GMT on November 12, 2010
Member Since: August 16, 2007 Posts: 0 Comments: 6213
586. JRRP
6:18 PM GMT on November 12, 2010
18 GMT 11/12/10 11.1N 76.2W 20 1009 Invest
Member Since: August 16, 2007 Posts: 0 Comments: 6213
585. xcool
6:16 PM GMT on November 12, 2010
Member Since: September 26, 2009 Posts: 2 Comments: 15684
584. AstroHurricane001
6:10 PM GMT on November 12, 2010


Looks like the Caribbean disturbance is developing an eye, similar to TD Tomas earlier this season. Floods in Colombia have killed over 200 people this year.
Member Since: August 30, 2008 Posts: 8 Comments: 2836
583. Minnemike
6:09 PM GMT on November 12, 2010
Quoting KEEPEROFTHEGATE:
AOI
XX/XX/94L
11.55N/75.98W

this must be the hold up on today's update... seeing that anti-cyclone in place before the convection fires... some nice instant outflow!
Member Since: July 31, 2008 Posts: 0 Comments: 1320
582. KEEPEROFTHEGATE (Mod)
6:07 PM GMT on November 12, 2010
AOI
XX/INV/94L
11.55N/75.98W
Member Since: July 15, 2006 Posts: 178 Comments: 56141
581. KEEPEROFTHEGATE (Mod)
6:04 PM GMT on November 12, 2010
2010 Storms
All Active Year


Atlantic
94L.INVEST

East Pacific

Central Pacific

West Pacific
90W.INVEST

Indian Ocean

Southern Hemisphere
Member Since: July 15, 2006 Posts: 178 Comments: 56141
580. 7544
6:04 PM GMT on November 12, 2010
thanks looks like 94l will go wnw for a while waiting on the runs
Member Since: May 6, 2007 Posts: 0 Comments: 6874
578. 1900hurricane
5:56 PM GMT on November 12, 2010
94L:

Member Since: August 2, 2006 Posts: 47 Comments: 11709
577. CaicosRetiredSailor
5:46 PM GMT on November 12, 2010


Member Since: July 12, 2007 Posts: 0 Comments: 6069
576. Neapolitan
5:44 PM GMT on November 12, 2010
Just out of the oven:

BEGIN
NHC_ATCF
invest_al942010.invest
FSTDA
R
U
040
010
0000
201011121739
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 94, 2010, DB, O, 2010111218, 9999999999, , , , , , METWATCH, , AL942010
AL, 94, 2010111218, , BEST, 0, 110N, 761W, 20, 0, DB, 0, , 0, 0, 0, 0,
Member Since: November 8, 2009 Posts: 4 Comments: 13803
575. KEEPEROFTHEGATE (Mod)
5:40 PM GMT on November 12, 2010
X
Member Since: July 15, 2006 Posts: 178 Comments: 56141
574. KEEPEROFTHEGATE (Mod)
5:36 PM GMT on November 12, 2010
Member Since: July 15, 2006 Posts: 178 Comments: 56141
573. KEEPEROFTHEGATE (Mod)
5:34 PM GMT on November 12, 2010
000
ABNT20 KNHC 121733
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
100 PM EST FRI NOV 12 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWERS AND THUNDERSTORMS OVER THE SOUTHERN CARIBBEAN SEA OFF THE
COAST OF COLOMBIA AND PANAMA ARE ASSOCIATED WITH A BROAD AREA OF
LOW PRESSURE. CONDITIONS APPEAR FAVORABLE FOR SOME DEVELOPMENT OF
THIS SYSTEM OVER THE NEXT COUPLE OF DAYS AS IT DRIFTS SLOWLY
WESTWARD OR WEST-NORTHWESTWARD. THERE IS A MEDIUM CHANCE...30
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

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

$$
FORECASTER BRENNAN


Member Since: July 15, 2006 Posts: 178 Comments: 56141
572. KEEPEROFTHEGATE (Mod)
5:34 PM GMT on November 12, 2010
we now fly 30 percent on AOI
Member Since: July 15, 2006 Posts: 178 Comments: 56141

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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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