Atlantic Hurricane Season 2008 Withers on the Vine
The North Atlantic hurricane season has nearly come to an end. As November progresses, the chance of another storm developing becomes smaller. Climatology (last 60 years) tells us that roughly 4 in 10 years see a November storm formation including 4 in 2005 (Beta, Gamma, Delta, Epsilon), Hurricane Michelle (2001), Hurricane Lenny (1999), and Hurricane Kate (1985). Jeff Masters from the Weather Underground has an image of previous early-November storm tracks especially clustered in the Western Caribbean.
So, what has the 2008 season wrought in the North Atlantic and how well did the seasonal prognosticators fare?
Even with the expected post-season tinkering of the real-time storm tracks by the folks at the National Hurricane Center, we can provide fairly accurate preliminary numbers. The community at Wikipedia constantly updates many interesting facts about the ongoing 2008 hurricane season.
Total Named storms (34 knots + one-minute maximum sustained winds): 15
Total Hurricanes (64 knots +): 7
Total Major Hurricanes (96 knots +): 4
Accumulated Cyclone Energy: 132
The respective forecasts made by CSU (Klotzbach and Gray), NOAA, as well as the UK Met Office came in quite close to the actual experienced storm activity. Before handing out trophies, please keep in mind that forecast “skill” is a function of many forecasts over longer time periods. Each of the forecasting outfits prefers to use different techniques and variables to calculate their storm numbers, so we will have to wait until each completes their post-season analysis to determine if they were “right for the right reason” or got lucky.
Now, to answer the question: how active was the 2008 hurricane season, we need to define climatology. This is where the tricksters can play pranks on the public. Where is the beginning point of the analysis? How well do we trust the frequency and the estimated intensities of each storm? What metric do we use – number of tropical storms, number of hurricanes, ACE (accumulated cyclone energy), Power Dissipation, or perhaps some complicated statistical measure? All of these questions are entangled in the debate surrounding whether anthropogenic climate change is indeed a modulating influence upon current and future Atlantic hurricane activity.
A well-accepted metric which convolves storm frequency, intensity, and duration is called accumulate cyclone energy (ACE) and is calculated very simply: take the maximum sustained winds reported by the NHC every 6-hours for all storms (> 34 knots), square this value, and sum over the entire lifetime, then divide by 10,000. In 2007, even though there were also 15 storms, the ACE was only 72 compared to 132 for 2008 with the same number of named storms. This is partially because the storms in 2008 were much longer lived especially Bertha.
Here are three different views of the Atlantic hurricane climatology depending upon what period you look at. The data is from the NHC Best Tracks without any corrections to the intensity data.
Links to two other time periods:
1978-2008
1944-2008
Thus, since 1995, Atlantic hurricane activity measured by ACE is hugely variable with feast (i.e. 2005) and famine (1997). 2008 ACE is nearly equivalent to 2006 and 2007 combined, but about half as what was experienced in the record 2005 season. The choice of 30-years is a particular favorite for many researchers in the tropical cyclone community (1978-2007). The second image clearly shows the nearly stepwise increase in ACE between 1994 and 1995. In this reference frame, 2008 ranks as one of the more active years of the past 30. Now, back up to 1944, when admittedly the intensity (and detection) data is somewhat less reliable. However, since the ACE metric is the convolution of an entire year’s worth of storm lifecycle information, and is most sensitive to higher wind speeds, the track data points prior to satellite observation (~1970s) are probably sufficient for this exercise.
Final verdict: When encapsulated in the recent active period in North Atlantic activity (1995-2007), 2008 experienced normal or expected activity as measured by ACE. In terms of a long-term climatology, either the last 30 or 65 years, 2008 is clearly an above average year.
Note: for the Climate Audit seasonal forecasters, especially those that showed exemplary skill (however you wish to measure it), please fill us in on your methodology and perhaps provide guidance for 2009. Or, for those feeling shame about being “blown off track”, time to think of good excuses.
Also, a new Science perspective has been published by Vecchi et al. (2008) entitled Whither Hurricane Activity? More on that later…
// Les Johnson (15:58:08) :
I will retire in Texas, on the gulf coast, in spite of the hurricane risk.
Why?
Because a hurricane only lasts a few hours. Winter lasts 8 months. //
But death lasts somewhat longer. I have been quite amazed at the accuracy of the science regarding the prediction of the path of these hurricanes. As these scientists can only be 90% accurate though why does anybody take any notice of them?
Philw1776 and Tom in Fla – If that is the case then it is just profiteering and can’t be defended. On the other hand, maybe they’re just running scared, scared by the rubbish sprouted by Al Gore et al.
Christian – “70+ mph winds and knocked out my power for two and a half days”.
I’ve been in that situation in a small country town in Australia – BUT it was not a hurricane or a tornado or… it was just a few gusts of very hard wind and heavy rain in a thunderstorm. Such things happen regularly, but not in the same place. Perhaps that’s just a bit of weather.
@MikeRossTky,
Relative neutral ENSO conditions, PDO tending towards cool too, and 18 Typhoons sounds like a good correlation to “only” 18 “so far” in 2008.
I did look up the http://agora.ex.nii.ac.jp/digital-typhoon/index.html.en
and the ACE data they show lists:
2004 – 29
2005 – 23
2006 – 23
2007 – 24
2008 – 18, [till Nov.1]
Is this some form of support of GW not true? Looks to me like 2008, so far, is an anomalous year against a 58 year mean of 23.1, with the ’04-’07 period clearly having an above mean.
There seems to be a reasonably good correlation between La Nina events and strong hurricane seasons, see:http://oceanmotion.org/html/impact/el-nino.htm
We had a strong La Nina early 2008, and an above average hurricane season.
Mike Dubrasich:”Katrina damage was mainly due to failed dikes. Flood damage, not direct storm damage. Haitian losses due to ill-preparations for a typical storm. Hurricane-related losses are not a direct function of wind speed in most cases. ”
The Katrina damage you state was only for New Orleans. Coastal Mississippi and Alabama were destroyed by storm surge and wind directly from that storm. The news only focused on New Orleans. Same with this year. I was speaking with a medical office in Baton Rouge after Gustav hit them and asked how they were doing. They were hit really hard with severe wind damage, power outages and flooding. What made them really mad was that no one seemed to care. They were incensed that as soon as New Orleans was in the clear all the reporters went home and the story was over.
The graphs would seem to correlate nicely with regime changes in the AMO, and one is reminded that the great Bill Gray was already warning during the blase ’70’s that an uptick in Atlantic tropical cyclone activity was a few decades down the road.
Though it was an active hurricane season , I have to say that as far I’m concerned , I have never seen so many storms affecting so many countries in the caribbean , central america and the gulf region in one single year .
By the way, Anthony, is that poster child ‘cane Floyd from 1999?
Floyd didn’t look so purdy by the time it huffed and puffed its way up here to 40 N, but it dumped 15 inches of rain in as many hours on central New Jersey, and the ensuing Floydian flood (not Floydian slip) knocked out a major water filtration plant for two weeks.
‘…no damage to property and deaths.’
Isn’t Texas still in the Union? How many missing and presumed dead on Galveston Island?
It doesn’t take a Cat 5 or even a major hurricane to cause grief
This was a fairly typical hurricane season, with typical storms.
It will be the AGW promoters who seek to extract evidence supporting their faith from this.
One thing to consider in re this last tropical season, is that many of the storms formed very close to land. One effect of this, e.g. with Faye, was that, even though upper level patterns were quite favorable for intensification, interaction with land, especially with mountainous Hispanola and western Cuba, inhibited development, while enhancing rainfall– sections of Florida got a half-year’s worth of rain in three days.
It also seems, on the shorter term, that ENSO phenomena are reflected in the graphs: strong El Ninos correlate with decreased tropical cyclone activity in the Atlantic and La Ninas with increased activity.
The opposite is true for the Southwest Pac, which leads me to wonder whether there are ACE figures available for the current typhoon season. The global ACE and its adventures over the past century would also be quite relevant in trying to grasp such cyclic patterns as can be discerned (Leif Svalgaard has wised me up on cyclomania as applied to systems with a significant chaotic input).
‘…so many storms affecting so many countries in the caribbean , central america and the gulf region in one single year .’
How about one storm that, in a week or so, brought hurricane conditions to every one of the Greater Antilles, and then to every state on the Atlantic coast of the U.S. from Florida (both coasts) to Maine?
That was Hurricane Donna in 1960–a year, by the way, with an anemic ACE.
‘Ike, a Cat2, had days to travel across the Gulf allowing a massive dome of water to build under it and then hit head on into the Galveston area destroying everything.
Another important factor is the depth and configuration of the continental shelf just off a given target area.
[…] whatever happened to that 2008 hurricane season? Watts Up With That? […]
Just for info, it seems that hurricane activity in the East Pacific has been normal or below normal for the last 10 years.
http://upload.wikimedia.org/wikipedia/commons/5/57/Hist_east_pac_ace_trend_1971-2007.gif
It might be my imagination, but I’ve noticed pictures of the Earth from the Apollo missions in the late 60’s show a very cloudy Earth. Modern pictures from space show a very clear earth.
Is there a difference in photo technology and filtering, or is there really that much less cloud cover?
Pretty cool – a hurricane in the Carribean and a bilzzard in the Dakotas. I have no idea when that happened last. (BTW, the blizzard may not meet a rigorous characteristic, the temperature is above 20F. However, the storm is turning 10″ of snowfall into 10′ of drifts, and ready drifting is one reason for the cold temperature requirement.
In the northeast, the NWS dropped the temperature requirement since coastal storms usually bring warm temps.
According to Wikipedia, NOAA defines normaility in terms of ACE for tropical storms and hurricanes in the Atlantic basin as follow:
“Measured over the period 1951–2005 for the Atlantic basin:
Median annual index: 89.5
Mean annual index: 102.3
A season’s ACE is used to categorize the hurricane season by its activity. NOAA categorisation system[3] divides them into:
Above-normal season: An ACE value above 103 (115% of the current median), provided at least two of the following three parameters exceed the long-term average: number of tropical storms (10), hurricanes (6), and major hurricanes (2).
Near-normal season: neither above-normal nor below normal
Below-normal season: An ACE value below 66 (74% of the current median):
In the Above-normal case, ACE median ~ 1.15*ACE Medain, whereas, in the Below-normal case, 0.65*ACE ~ 0.74*ACE Median. This stikes me as rather odd. I would have thought the boundaries would have been more symmetrical. Can anyone help me, or direct be to a reference source that might help me, understand the reasoning for defining the categories this way?
Re: My last message
“In the Above-normal case, ACE median ~ 1.15*ACE Medain, whereas, in the Below-normal case, 0.65*ACE ~ 0.74*ACE Median.”
should read:
“In the Above-normal case, ACE Mean ~ 1.15*ACE Median, whereas, in the Below-normal case, 0.65*ACE Mean ~ 0.74*ACE Median.”
Sorry about that …