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EmailHere is the summary of 2011 Northern Atlantic hurricane activity, according to experts, plus answers to readers' commonly-asked questions about hurricanes.
"The 2011 Atlantic basin hurricane season had activity at above-average levels, though not to the level that was expected in our pre-season forecasts. While anomalously warm tropical Atlantic SSTs and La Niña conditions likely provided conditions that were reasonably favorable for an active season, anomalously cool SSTs in the northeast subtropical Atlantic, anomalously dry mid levels in the tropical Atlantic and a positive Indian Ocean Dipole (IOD) event conspired to put a damper on this season’s more intense tropical cyclone activity. A weakness in the subtropical ridge located near the East Coast helped induce the recurvature of several systems that might otherwise have threatened the U.S. coastline."–Colorado State University
There were 19 named storms—an impressive number—but many of these storms were weak; the intense hurricanes were just slightly above-average; no Category 5 hurricane formed.
Fortunately, no major hurricanes made US landfall in 2011, despite a forecast of above-average probability. In fact, no major hurricanes have made landfall in the U.S. in six years!
2011 Atlantic Basin Seasonal Hurricane Summary
(Issued November 30, 2011 by CSU)
The hurricane season runs June 1 through November 30; this historical average (in parenthesis) is based on 1950–2000 records.
| Forecast Parameter (1950-2000 Climatology) | Observed 2011 Total |
|---|---|
| Named tropical storms (9.6) | 19 |
| Named tropical storm days (49.1) | 90.50 |
| Hurricanes (5.9) | 7 |
| Hurricane days (24.5) | 25 |
| Major hurricanes (2.3) | 3 |
| Major hurricane days (5) | 4.50 |
| Net tropical cyclone activity (100%) | 137% |
Note: Forecasts cover the Atlantic Basin—the area encompassing the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Get up-to-the-moment hurricane news at the NOAA National Hurricane Center.
Hurricane Names
See tropical storm names for 2012.
Most storm names are taken from a permanent list that rotates every 6 years. More than 60 names have been retired since 1950 because they resulted in significant property damage or deaths, including Camille (1969), Agnes (1972), Carmen (1974), Hugo (1989), Andrew (1992), Mitch (1998), Floyd (1999), Lili (2002), Dennis (2005), Katrina (2005), Rita (2005), Stan (2005), Wilma (2005), Dean (2007), Felix (2007), Noel (2007), Gustav (2008), Ike (2008), Paloma (2008), Igor (2010), and Tomas (2010). A name can be retired at the request of a country affected by the storm. It should be noted that not all hurricanes were named, including some of the most deadly or damaging storms known to man.
Q. How many hurricanes can we expect during any given hurricane season in the Atlantic Ocean?
A. Each year an average of ten tropical storms develop in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Six of them, on average, will actually achieve hurricane status. Many of these storms will die out over the ocean.
Q. Just what is a hurricane?
A. A hurricane is a tropical storm with winds that have reached a constant speed of at least 74 mph in the North Atlantic Ocean, Caribbean Sea, or Gulf of Mexico. A hurricane's winds blow in a large spiral around a relatively calm center of extremely low pressure known as the eye of the storm. Around the rim of the eye, winds may gust to more than 200 mph. The eye of a storm is usually 20 to 30 miles wide and may extend over 400 miles. The entire storm can be up to 340 miles in diameter, dominating the ocean surface and lower atmosphere for thousands of square miles.
The dangers of a storm include torrential rains, high winds, and storm surges. A hurricane can last for 2 weeks or more over open water and can follow a path across the entire length of the eastern seaboard, coastal areas, and barrier islands. All Atlantic and Gulf coastal areas are subject to hurricanes or tropical storms. Although rarely struck by hurricanes, parts of the Southwest and Pacific Coast suffer heavy rains and floods each year from the remnants of hurricanes spawned off Mexico. Islands such as Hawaii, Guam, American Samoa, and Puerto Rico also are subject to hurricanes.
Q. Is a hurricane the same as a cyclone?
A. A hurricane is actually one of three kinds of tropical storms, or cyclones, that circulate over tropical waters. The circulation is counterclockwise in the Northern Hemisphere. Tropical cyclones are classified as follows:
-
Tropical depression
An organized system of clouds and thunderstorms with a defined circulation and maximum sustained winds of 38 mph (33 knots) or less.
-
Tropical storm
An organized system of strong thunderstorms with a defined circulation and maximum sustained winds of 39 to 73 mph (34 to 63 knots).
-
Hurricane
An intense tropical weather system with a well-defined circulation and maximum sustained winds of 74 mph (64 knots) or higher. In the western Pacific, hurricanes are called typhoons. Similar storms in the Indian Ocean are called cyclones.
Hurricanes are further classified by rank according to how strong their winds are.
Q. How are hurricanes classified?
A. The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity. This is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf in the landfall region. Wind speeds are measured using a 1-minute average.
| Saffir-Simpson | Hurricane | Scale | Average | Wind | (mph) | Representative Hurricanes | |
|---|---|---|---|---|---|---|---|
| Category One | 74 - 95 | Danny; 1997 | |||||
| Category Two | 96 - 110 | Bonnie & Georges; 1998 | |||||
| Category Three | 111 - 130 | Rita; 2005 | |||||
| Category Four | 131 - 155 | Charley; 2004 | |||||
| Category Five | 156 + | Andrew; |
| 1992 |
Q
. What causes a hurricane to happen?
A. A tropical ocean and its atmosphere create the right conditions for a hurricane. Hurricanes draw their energy from the warm surface waters of the tropics (usually above 27°C, or about 81°F) and the latent heat of condensation. Powered by heat from the sea, they are steered by the easterly trade winds and the temperate westerlies, as well as by their own ferocious energy. Around their core, winds grow with great velocity, generating violent seas. Moving ashore, they sweep the ocean inward while spawning tornadoes and producing torrential rain and floods. When hurricanes move over cold water or over large landmasses, they can die out quickly because they lose the power of the heat and condensation.
Q. How do we know a hurricane is coming?
Now, thanks to satellite technology, no hurricane goes unnoticed. See our article on "Predicting Hurricanes: The Eyes Have It" to learn more.
Q. What do the hurricane warnings mean?
A. A watch means that hurricane-force winds are possible within 48 hours. A warning means that hurricane-force winds are likely within 36 hours.
Q. What caused Hurricane Katrina?
A. Hurricane Katrina (2005) was one of the five deadliest hurricanes to ever strike the country and also the single most costly hurricane. The damage and loss of life inflicted by this powerful hurricane in Louisiana and Mississippi were devastating, with effects stretching into Florida panhandle, Georgia, and Alabama.
Katrina was a complex storm, but to put it simply: Katrina started with the interaction of a tropical wave and the remnants of a weakening storm known as Tropical Depression Ten; the pressure disturbance become organized over the central Bahamas on August 23. It rapidly strengthened into a tropical storm and then a hurricane by the next day. Katrina was lifted towards Florida by upper-level steering winds and became a category 1 hurricane a few hours before landfall in southern Florida on the 25th. Katrina was on shore for about 7 hours and then moved into the Gulf of Mexico, reaching category 5 intensity on August 28. Katrina weakened to a strong category 3 or category 4 hurricane before making landfall on the northern Gulf coast.
Q. How will hurricanes affect the oil spill in the Gulf Coast?
A. Experts have little knowledge about the affect of hurricanes on oil spills, and vice versa. One thing they do know is that any movement of oil is completely dependent on the track and scope of the particular hurricane. Because a hurricane's winds move counter-clockwise, the direction of oil transport would be altered depending on which direction the hurricane is tracking. For more answers regarding the oil spill and hurricanes, please see: Hurricanes and the Oil Spill Factsheet, NOAA.
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Comments
Okay, I'm in southern
Okay, I'm in southern NH..Milford,besides the handy weatherman how can I tell if "Irene" is gonna get us good or just alot of hype??
There is another free
There is another free resource for hurricanes and long range weather at weathersage.com that includes weekly information through Sept. 21st. Thanks
I read about hurricane in my
I read about hurricane in my school days though I didn't get much information about hurricane in my school books, but here I get more information about hurricane. I didn't know hurricane nine names. And here in our country no hurricane is formed and occur, but I see in T.V. Thank you for providing a lot of information about hurricane. Now, I tell about hurricane to my younger ones. :)
The hurricane is gaining
The hurricane is gaining strength. Boats are being hauled ashore and water sport businesses are canceling reservations. Ferry trips are also canceled. Just barely a hurricane, this is the sixteenth tropical storm this year. The barely-a-hurricane Paula has already hit Mexico. Honduras and a few other nations are also in danger. Hurricane Paula - Category 1 storm ponds Mexico and Honduras. The storm isn't anticipated to strengthen, but it's predicted to continue to do serious destruction for a few days. This storm is sure to produce heavy rains that could cause flash floods and mudslides. Residents should keep an eye on it, and prioritize their safety.
The information regarding
The information regarding watches and warnings was changed this year by the National Hurricane Center. Watches are issued 48 hours before forecast storm landfall. Warnings are issued 36 hours before forecast storm landfall. Please update the information pages, which are excellent other than this data point.
Bob Gaffney
Thank you, Bob. We have
Thank you, Bob. We have updated this page with the latest Hurricane Watch and Hurricane Warning definitions from the NOAA Hurricane Center.
Thanks for your comments,
Thanks for your comments, folks.
Ryderman, re the oil spill and hurricanes: There seem to be a lot of opinions and predictions of how a hurricane might effect the spill (and how the spill might effect a hurricane), but—it appears from numerous sources—nothing specific/exacting to base them on, as a situation such as exists in the Gulf has never occurred.
I am sure you, too, have your sources, but that is a statement from National Public Radio (NPR.org; link to follow); note that the key word is "could": "If a hurricane encounters the oil slick now covering parts of the Gulf of Mexico, the result could be devastating, scientists say. Not only could any hurricane increase the damage that oil does to coastal wetlands, but the presence of oil could lead to a more powerful hurricane, they say. Nobody knows for sure, though, because there's no record of a hurricane ever crossing paths with a large oil spill." That's here: http://www.npr.org/templates/story/story.php?storyId=127036434
The National Oceanic and Atmospheric Administration (NOAA) has created a response to questions about how a hurricane might effect the spill; see here: http://www.nhc.noaa.gov/pdf/hurricanes_oil_factsheet.pdf
That link above is actually from this page (link below), which shows the temp of Gulf and Caribbean waters in vivid orange: http://earthobservatory.nasa.gov/IOTD/view.php?id=44166&src=eoa-iotd
So, we'll see.
Cory613, we do forecast hurricanes in our weather predictions. In the General Weather Forecast (page 81 in the 2010 edition), we make this statement: "Although the hurricane season will not have a high number of storms, there may be major hits in Florida [Region 5; see page 210 or the region on this Web site http://www.Almanac.com/weather/longrange) near Labor Day and in the Deep South [Region 8, ditto the Web site] in late September."
It remains to be seen if indeed the U.S. experiences a high count of hurricanes this season, as many sources are predicting.
All I can say again is "we'll see." We're all in it together. Thanks again for your comments. Have a great day!
I heard a man speaking, a
I heard a man speaking, a scientist I believe from the Gulf Coast Association, he was describing how back in 1979 when we had a very huge and devastating oil spill, far greater than our current 2010 oil spill....how a hurricane "healed" the effects of the oil spill almost immediately afterwards. He also described the hurricane as natures washing machine for cleansing our earths "grime". Any comments from you are appreciated.
In 79 there was not the same
In 79 there was not the same access to technological information as we have now. If a huge hurricane was the world's washing machine, where did all the oil, dirt and grime filter to? It went somewhere no? So although we do not see all the grime and dirt left by us, it still exists and poisons us but we are not as aware of it's existence because it has been broken up into smaller peices. But that doens't mean it's gone. The particles may still be leathal.
Why aren't hurricanes in your
Why aren't hurricanes in your long range weather forcasts ?
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