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
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22nd including depressions
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.
Amazing looking invest. May have a TD by sunday IMO.
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.
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
AAAAAK! I messed that one up...
2005 - mea culpa...
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
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.
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
TSPIN BUSTED FORECAST ALIBI
Yes, I blew the call... my bad...
Any thoughts?
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