Atmosphere And Weather

The Life Cycle of a Hurricane



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"The Life Cycle of a Hurricane"
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From it's start as a tropical disturbance, hurricanes feature heavy rain, thunderstorms, and wind gusts. Storms aren't only dangerous when the storm reaches category 5 status with winds above 155 mph. Every stage of a hurricane's life cycle presents a threat to life and property. Hurricanes can spread incredible destruction, even after making landfall as downgraded tropical storms.

The best way to understand the life cycle of a hurricane is to look, step by step, at the life of one hurricane. In September 2003, Hurricane Isabel caused extensive damage along the North East Coast, despite the fact that it was no longer an actual hurricane. Maryland doesn't experience many hurricanes, thankfully. However, in my lifetime, two storms stand out. Hurricane Agnes in 1972 and Hurricane Isabel in 2003. I remember the pounding rain of Agnes as a 4-year-old child. I remember fearing for my life as an adult with a small child in 2003.

Tropical waves

Hurricanes begin as tropical "waves" or collections of clouds in the Atlantic. Not just any cloud can become the seed of a monster storm. Tropical waves are low-pressure troughs of wind that blows east to west. Isabel began her life as a tropical wave near the Cape Verde Islands off the coast of Africa. Isabel found everything she needed for fuel near these islands: deep and warm, 80-degree ocean water and light upper winds. This gentle environment helped organize this young storm.

Tropical depression

Isabel became a tropical depression quickly, organizing into a system of clouds and thunderstorms with minor wind circulation patterns. Isabel began to assume her spiral shape at this stage and her winds as tropical depressions did not exceed the 38 mph limit for a depression. At this stage, low barometric pressure can be measured at the center of these thunderstorm clusters; another feature of a developing hurricane.

Tropical storm

Isabel graduated from a tropical depression to a tropical storm in the space of a day. She received her official name, as all storms do, and continued on a north, northwest path across the Atlantic Ocean. Isabel graduated from tropical depression to tropical storms as her winds reached 39 mph. Tropical storm force winds can range from 39 to 73 mph. During this tropical storm stage, the eye develops at the center of the storm from sinking air that dries and warms the center of the storm. The eye contains clear weather and light winds. Just outside the eye, the eye wall is developing its distinctive towering shape.

Tropical cyclone (hurricane)

Isabel's eye, eye wall, and spiral rain bands formed rapidly and Isabel became a full-blown hurricane. She went through many changes as a hurricane. In the space of a day, she flip-flopped from Category 4 to 5 as her eye wall degraded then reformed. Isabel attained Category 5 status three times before eventually downgrading to a Category 2 and making landfall on North Carolina's Outer Banks with 105-mph winds.

Back to a tropical depression

Isabel quickly downgraded to a tropical depression again due to the friction caused by the storm moving over land. However, she gained speed, barreling through Virginia on a path towards Western Maryland. The dangerous right side of the hurricane passed over North Carolina, Virginia, Maryland, Pennsylvania, and the Chesapeake Bay. When Isabel passed over Maryland, an 8-foot storm surge was recorded in Baltimore Harbor. Tides in the Bay were 8 feet above normal. An estimated 20 acres of sand was removed along the coastline, causing severe beach erosion. Peak inland winds were clocked at 83 mph in Silver Spring, a suburb of Washington, D.C. Parts of Kent Island at the Bay Bridge were completely under water.

Isabel did her damage in Maryland at night. We had plenty of preparation time. Most government offices, schools, and businesses closed for the entire day before the storm. Businesses along the Potomac River waterfront sandbagged storefronts against flooding. All Washington, D.C. airports were closed. Over 40 Navy ships and subs were sent to sea from Norfolk bases. Folks enjoyed their last few hours of electrical power. There was an expectation in the air, almost like energy, an overwhelming feeling of pure dread.

I remember standing out on my deck, watching the flashing blue lights in the sky that preceded the major part of the storm. That night was one of the longest of my life as wind gusts and rain pounded my townhouse. Isabel caused extensive damage with downed trees and power lines, partly because the ground was already saturated from heavy rains. Over 6 million people were left without power on the East Coast. Over $3.6 billion in damages amounted from this storm and 47 people died.

Extra tropical storm

Isabel became an extra tropical storm when she passed into Pennsylvania. But she still caused extensive flooding, power outages, tree damage, and two fatalities. She wasn't done yet. Isabel affected every state along the East Coast and continued to cause flooding and power outages well in Canada. Isabel was eventually absorbed into another weather system over Ontario. The name Isabel was retired after the 2003 season.

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