With Tropical Storm Isaac planning its assault on the National Republican Convention in Tampa and Tropical Storm Joyce spinning out in the Atlantic close behind, it appears that the 2012 Atlantic Hurricane season is heating up fast.
For East Coast surfers and weather junkies alike, this is the most exciting time of the year. For insurance companies and coastal homeowners, the uncertainty about what potential destruction lies ahead is nerve rattling to say the least. There is one thing East Coast residents can be sure about though: over the next month, names like Katrina, Andrew, Ike, and Irene will re-enter our vocabularies alongside the names of this year’s storms as we glue ourselves to TV sets to watch and wait for mother nature’s most awesome storms to descend.
Here is quick overview of everything you need to know about hurricanes and what you can expect from this hurricane season.
How Do Hurricanes Work?
Hurricanes initiate when warm air rises from the ocean. Convergent winds force the warm air into the atmosphere where it condenses into clouds and rain. Pushed by the trade winds, these disturbances coalesce to a spinning mass of thunderclouds, growing as warm moist air sweeps into the low pressure void.
Before these disturbed weather patterns are hurricanes, they are tropical depressions, which are defined at the first appearance of a low-pressure organized circulation at the center of a group of thunderstorms. Winds near the center of a tropical depression are constantly between 23 – 39 MPH. Once a tropical depression has intensified to the point where its maximum sustained winds are between 39-73 MPH, it becomes a tropical storm and is assigned a name. A tropical storm becomes a hurricane when sustained wind speeds exceed 74 MPH.
Tropical Cyclone and Hurricane Category Definitions
The central area of lowest pressure of a hurricane is known as the eye, a calm, cloud-free area from 4 – 40 miles across. Immediately surrounding the eye is the eye-wall, a cylindrical band containing the highest winds and most concentrated violence of the storm. Air at the sea surface is sucked towards the eye and thrust up the eyewall after forming rain bands on the trip inwards. The moist air cools as it rises, causing water to condense as a mist or ice while releasing large amounts of heat. This liberated heat causes air to rise even further, producing more condensation and releasing even more heat. In this manner, a hurricane drives itself by pulling in warm moist air at its base, extracting heat and water, and propelling the air outward near elevations of 50,000 feet.
How Hurricanes Work
The most destructive part of a hurricane occurs on the right side of the counter-clockwise rotating storm. Here the forward motion of the hurricane adds speed to the counter-clockwise spinning winds. Simultaneously, low atmospheric pressure allows sea levels to bulge under the hurricane. This sea bulge in combination with strong currents and large waves become a life-threatening flood called a storm surge, which depending on the topography, can extend inland many miles, reaching up to 25 feet above mean sea level. When the storm surge hits in conjunction with a high tide, its height and potential for destruction is increased even further.
How Storm Surges Work
When Do Hurricanes Occur?
NOW! We have entered the busiest part of the hurricane season. Officially, Atlantic hurricane season runs from June 1 – November 30, but most of the action occurs between August 20th and October 1st, with September 10 being the peak of the season. Based on the graph below from our friends at NOAA, it looks like the next three weeks would be the worst time of year to plan your trip to the Caribbean or to, say, TAMPA, FLORIDA.
When Hurricanes Occur
How Much Do Hurricanes Cost?
Storm surge flooding, high winds, tornadoes, and rain associated with hurricanes put a big dent in the U.S. economy every year. The median cost of an Atlantic hurricane that hits land in the United States is $1.8 billion. In terms of cost of life, an average of 114 people have died each year as a direct result of hurricanes over the last 10 years. That said, the cost of a single hurricane can be many times more costly. Hurricane Katrina caused an estimated $106 billion in damage in 2005 and caused at least 1,500 directly related fatalities, most of which were the result of storm surge inland flooding.
The deadliest hurricane in U.S. history was the Great Galvaston Hurricane of 1900, a Category 4 hurricane which hit Texas with an estimated storm surge of 16 feet (stop and think about that for a second). This storm claimed approximately 8,000 deaths and is noted as the worst natural disaster in our country's history.
Costliest US Hurricanes in US History
Deadliest Hurricane of the Last 50 Years
The 2012 Hurricane Outlook: What to Expect
This year’s hurricane season is expected to be busier than normal, due to currently warmer than average sea surface temperatures in the Atlantic. To date, we have seen 10 tropical storms, 3 hurricanes, 0 hurricanes above category 3 in the Atlantic. There have been 24 hurricane associate fatalities so far in 2012 and $60 million in damage has occurred. 2012 is also the first year since record keeping began in1851 to have four named storms before July.
“We are increasing the likelihood of an above-normal season because storm-conducive wind patterns and warmer-than-normal sea surface temperatures are now in place in the Atlantic,” said Gerry Bell, Ph.D., lead seasonal hurricane forecaster at the Climate Prediction Center. “These conditions are linked to the ongoing high activity era for Atlantic hurricanes that began in 1995. Also, strong early-season activity is generally indicative of a more active season.”
Across the entire Atlantic Basin for the 2012 hurricane season, NOAA’s hurricane prediction for number of storms is as follows:
2012 NOAA Hurricane Outlook
NOAA seasonal climate forecasters also announced that El Niño will likely develop in August or September. El Nino is a competing factor because it strengthens the vertical wind shear over the Atlantic, which suppresses storm development. El Nino, however, is not expected to have an impact until much later in the season.