Is the Atlantic hurricane season getting longer?
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
Reader Comments
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+1
Our next possible troublemaker for the Caribbean:O).
This WU blog is truly a piece of work.
Tomas did $500 million in damages there. Haiti lost 21 people, and over 5000 homes were damaged. Curacao had $28 million in damages, $10 million from explosions due to lightning.
And people are upset here in the CONUS because we haven't had a CAT 3 hit!!!
The sane sigh relief
Freaks.
True dat....Thanks Pat
Thanks for the Kind words today.
Thanks for your service, Patrap! I'd buy you a Macko if I could.
I'll raise a Foamy Glass High for you and all Veterans this afternoon here.
click pic for loop
Thanks for your service too:)
You are our WUnderful One's.
Tropical Update
Interesting blog, doc foretold Tomas's future in 2008! :P
Reliable timeframe, very reasonable to conclude we might see TD 22 on Monday or Tropical Storm Virginie.
THANK YOU!
Seems like a very appropriate time to do so; the science behind the initial post is still very timely, and this year seems to be a decent indicator of the theory.
Thanks for your service Pat!
and thanks to any others on here that served as well!
oh, and thanks for the update Dr. Masters
must be getting close to thanksgiving
Thanks for your service, Gro!
It's called "recycling" - we are all being told to "reduce, re-use and recycle"...
And if it is pertinent, as it is, why not:)
SPC AC 111710
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1110 AM CST THU NOV 11 2010
VALID 121200Z - 131200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
POSITIVE-TILT MID-LEVEL IMPULSE OVER THE SRN ROCKIES WILL SWING EWD
ACROSS THE SRN PLAINS ON FRIDAY...THEN BECOME ABSORBED INTO THE NRN
STREAM UPPER LOW OVER THE UPPER MS VALLEY BY FRIDAY NIGHT.
CONTINENTAL POLAR AIR MASS BUILDING OVER THE HIGH PLAINS TODAY WILL
SLOWLY MOVE SEWD INTO THE MID-MS VALLEY AND THE GREAT PLAINS BEHIND
A WEAK SFC LOW MIGRATING NEWD ALONG THE FRONT ON DAY 2. PORTIONS OF
THIS FRONT WILL BE THE FOCUS FOR CONVECTION FRIDAY AND FRIDAY NIGHT.
...SRN PLAINS...
TONGUE OF PRECIPITABLE WATERS AVERAGING 1 TO 1.25 INCHES GATHERING
IN E TX WILL SURGE NWD TODAY AHEAD OF THE PREVIOUSLY MENTIONED
MID-LEVEL WAVE. POSITIVE-TILT NATURE TO THE IMPULSE WILL ONLY
RESULT IN A MODEST INCREASE IN MID-LEVEL LAPSE RATES AND FRIDAY
AFTERNOON THERMAL BUOYANCY WILL BE LIMITED. HOWEVER...INCREASING
LARGE SCALE ASCENT AND IMPROVING DEEP-LAYER SHEAR PROFILES WILL
RESULT IN A MARGINALLY-SUPPORTIVE SEVERE THUNDERSTORM ENVIRONMENT
AMIDST MLCAPES 200-500 J/KG. THIS WILL ESPECIALLY BE THE CASE IF
SURFACE-BASED THUNDERSTORMS CAN FORM WITHIN THE WARM SECTOR FROM
NCNTRL TX INTO CNTRL/ERN OK FRIDAY AFTERNOON/EVENING BEFORE BECOMING
UNDERCUT BY THE SURGING COLD FRONT.
PRIMARY THREATS WILL BE GUSTY WINDS/HAIL APPROACHING SEVERE
CRITERIA. WIDESPREAD SEVERE THUNDERSTORMS ARE NOT LIKELY AND THE
SEVERE THREAT SHOULD DIMINISH RAPIDLY DURING THE EVENING.
..RACY.. 11/11/2010
On behalf of all of us, thanks TD.
I also wrote about the potential set up for severe weather on friday, but seems like that wont happen.
just kind of neat to have somewhat accurately forecast snow :pp
link to my blog
THANK YOU PAT for serving to for the Voice of Freedom for me and all believers in this Great Country and the many that believe in the fight for Freedom as well. Thank you Sir!
A slide show tribute to our armed forces. Thank you for your sacrifices!!!!
link
link two
Thanks,hydrus. Proud to do it.
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