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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If that pans out, gonna get cold for Thanksgiving and after.
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Quoting RitaEvac:


Looks like Arctic blast watching is about to begin in the tropical blogs.

Cool a tropical feature and Santa Claus coming to town at the same time :O)!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting RitaEvac:


Looks like Arctic blast watching is about to begin in the tropical blogs.

The Ft Worth NWS office discussed the Polar Vortex on 11-10-10 at 9:37AM in their Area forecast discussion..

Polar Vortex=Freezing cold temps for TX :O)
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:
Cool, the Polar Vortex moves into the US for Thanksgiving and a new invest is having a party in the Caribbean Sea and 3 ' of snow has fallen in Amarillo, TX this morning.

And who said the weather is boring??????


Looks like Arctic blast watching is about to begin in the tropical blogs.
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518. Jax82
GOM Forecast SST

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Quoting hydrus:
Yes it has. Its starting to form a pinhole eye.:)...Good morning..Got Geritol.?

When you're through with the Geritol, send it to me :O)
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Check out Tequnapeck or whatever its called on the Pacific side, major cool down of the water, weird what strong winds can do to cool off waters

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Cool, the Polar Vortex moves into the US for Thanksgiving and a new invest is having a party in the Caribbean Sea and 3 ' of snow has fallen in Amarillo, TX this morning.

And who said the weather is boring??????
Member Since: August 25, 2009 Posts: 20 Comments: 6785
514. Jax82
Still plenty warm enough in the Carribbean.

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Complete Update






TSPIN BUSTED FORECAST ALIBI
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nosing into Montana on the 24th, once this air dives down, its hard to stop it...

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23rd of thanksgiving week, massive 1040mb ridge coming down pike

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ok guys I am hearing we have pre-invest 94L/curently be invested into the family of invest/possibe storms yep guys talk to me
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Looking at the GFS model long range, it had a massive 1040+mb ridge up in Yukon, with some very cold air up there, if that were to pan out, the lower 48 would get its first arctic blast of the season.
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Quoting GeoffreyWPB:
0930 AM EST FRI 12 NOVEMBER 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 13/1100Z TO 14/1100Z NOVEMBER 2010
TCPOD NUMBER.....10-164

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
3. ADDITIONAL DAY OUTLOOK: PROBABLE LOW LEVEL INVEST
NEAR 12.5N 79.0W AT 15/1800Z.
I think we will have a invest soon Geoff..
Member Since: September 27, 2007 Posts: 1 Comments: 21183
0930 AM EST FRI 12 NOVEMBER 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 13/1100Z TO 14/1100Z NOVEMBER 2010
TCPOD NUMBER.....10-164

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.
3. ADDITIONAL DAY OUTLOOK: PROBABLE LOW LEVEL INVEST
NEAR 12.5N 79.0W AT 15/1800Z.
Member Since: September 10, 2007 Posts: 0 Comments: 11150
Quoting Grothar:


Hasn't changed much in 15 minutes.
Yes it has. Its starting to form a pinhole eye.:)...Good morning..Got Geritol.?
Member Since: September 27, 2007 Posts: 1 Comments: 21183
Quoting GeoffreyWPB:


Hasn't changed much in 15 minutes.
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Member Since: September 10, 2007 Posts: 0 Comments: 11150
Quoting jeffs713:


LOL.

I don't know which is worse... that you actually took the time to figure that out, or that you actually posted it.

Didn't have to do much figuring; I've got a timer on my desktop with the countdown to several important events ticking away... ;-)
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Quoting clwstmchasr:


I'm still waiting for that 2010 "pattern change" that was going to drive storms directly at the U.S.
lol..
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Quoting Neapolitan:
Just 200 days, 9 hours, and 41 minutes until the 2011 hurricane season officially gets under way...

;-)


go go gadget double-post!

-.-
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Quoting Neapolitan:
Just 200 days, 9 hours, and 41 minutes until the 2011 hurricane season officially gets under way...

;-)



LOL.

I don't know which is worse... that you actually took the time to figure that out, or that you actually posted it.
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Just 200 days, 9 hours, and 41 minutes until the 2011 hurricane season officially gets under way...

;-)

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The 2008 Jackson tornado....Link
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In the blink of an eye, residents across the Southern US watched as a series of tornadoes destroyed homes and took lives. The storms moved into the area without much warning as many residents didn't even have time to take cover. At least 52 people are reported dead as volunteers and emergency crews work to dig through piles of rubble in the search for survivors. These severe thunderstorms that developed into tornadoes ripped through Arkansas, Tennessee, Kentucky, Mississippi and Alabama unabated. Tennessee was the hardest hit state with 24 deaths reported making this the worst storm to hit middle Tennessee in 75 years since an F4 tornado on MAY 10, 1933.
Member Since: September 27, 2007 Posts: 1 Comments: 21183
Yes Virginia...There is still a hurricane season.
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Quoting Jeff9641:


A very highly amplified jet is usually the result from La-Nina's. Remember 2008! Tornado season started in January and Tenn. was the bulls-eye which seems to be the case when La-Nina occur.
Tell me about it...Severe weather, tornadoes kill dozens across South
TORNADO

February 06, 2008



Tornadoes and storms in the mid-South have killed 55 people since Tuesday evening in the deadliest tornado outbreak in the United States in more than 20 years.

The storms ripped apart homes and trapped residents of university dorms and a retirement home in debris.

The trail of death stretched across four states, with four people killed in Alabama, 13 in Arkansas, seven in Kentucky and 31 in Tennessee.

In some cases, there was almost no warning before the severe weather hit.
Member Since: September 27, 2007 Posts: 1 Comments: 21183
Quoting GeoffreyWPB:
Invest 94L about to be initiated.
This Storm has the best chance to become a virginie. the GFS is still showing walter after Virginie dissipates.
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Quoting Jeff9641:
2011 could be very very deadly and destructive for the US not only from Hurricanes but I think we are also setting up for one hell of a tornado season.
Not to sound disagreeable, but I hope you are wrong about the tornadoes. Some of us are still cleaning up from the last ten years worth...I hate tornadoes. Saw a good sized funnel pass a mile to the north of my house a couple weeks ago..
Member Since: September 27, 2007 Posts: 1 Comments: 21183
GOES-12 Atmospheric Imagery

These images are primarily for use in tropical storm monitoring. There are several areas to choose from providing a large-scale view of the Atlantic, down to the Gulf of Mexico. During hurricane season, the hurricanes page provides a variety of GOES atmospheric products to help monitor the active storms.

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Quoting Jeff9641:
Looking at the models we may squeeze 2 storms out of this area over the next 3 weeks.
I predicted that would happen 100,000 years ago..:)
Member Since: September 27, 2007 Posts: 1 Comments: 21183
Just wanted to repeat something mentioned last evening that may have been lost in the shuffle (and forgive me if this has been brought up already): the NHC best track data for Igor (KMZ [Google Earth] file) currently shows him as a Cat 5 for a single TWO (9/15 @ 0000 UTC). I'm not sure whether that will be reflected in the TCR when that's released in the next month or so, but it'll be interesting to see whether it is; if so, that would, of course, make Igor the first Cat 5 since 2007's Felix.
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AOI
xx/xx/xx
MARK
12.56N/75.98W
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The season aint over yet!!!
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morning
most of the models continue to show cyclogenesis north of Panama in the 0z runs today. the area looks prime for tropical activity. shear is down to 5-10, sst 29 deg C with good convergence and divergence. this morning's 850mb vorticity chart shows an elongated area which is over the north west part of south amrica. eventually this will shift over the warm waters of southwest caribbeanlooking at the steering currents it lloks lie the disturbance will skirt the honduras/Nicaragua peninsula, and then turn northeast towards eastern Cuba ,Jamaica and Haiti
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Pre-Virginie?
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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.