Hurricanes & Tropical Storms
A tropical storm is an organized storm that develops over warm ocean waters. When a tropical storm gets strong enough (winds over 74 mph), the storm is classified as a hurricane.
A hurricane is a large, swirling storm consisting of the Eye, which is usually partly cloudy or sometimes even clear with relatively calm winds. Then there's the eye-wall
where all of the strongest winds and storms occur. Then there are rain bands and outer rain bands which can stretch for hundreds of miles from the eye center. These storms and rain
bands generally get progressively weaker as they get farther from the eye.
Although residing usually over water, hurricanes sometimes can strike land. As a hurricane travels, it is constantly
sucking up the air around it as fuel, which includes the warm moist tropical air it forms in. This rushing air into the storm 'piles up' ocean water beneath the storm,
effectively dragging this heap of ocean water around as the hurricane travels. If a hurricane strikes land, this pile of extra ocean water then comes ashore --
known as a storm surge. The storm surge along with extremely heavy rains cause the flooding associated with a hurricane landfall, which accounts for most fatalities from a
How Tropical Storms & Hurricanes Develop
A tropical storm begins its life over warm, moist tropical waters. Conditions are most favorable from June 1 to November 30, which is the typical 'Hurricane
Season' in the North Atlantic Ocean. It starts May 15th in the Eastern North Pacific. This is when ocean waters are the warmest and atmosphere is most moist, which are perfect
hurricane forming conditions.
- Ocean water temperatures over 80 degrees farenheit
- Weak vertical wind shear
- Unstable atmosphere where temps decrease with height
- Moist mid levels of the atmosphere
- Typically at least 200 miles from the equator to spin, due to the Coriolis Effect.
Once you get a few storms to develop in an area under these conditions it becomes a 'tropical disturbance'. Further development of the storm takes it to 'tropical depression' where
rotating storms have winds of 38 mph or less. The next stage is 'Tropical Storm' when these winds reach 39 mph, and then eventually to Hurricane if the storm continues to organize
and strengthen to 74 mph.|
Once a storm matures, it can spin into a spiral of storms that spin around an eye. This 'eye' of the hurricane is often with few clouds and light or even calm winds.
Sometimes the eye can even be clear enough to see stars. The eye is surrounded by the strongest storms of the hurricane in what is known as the 'eye wall'. The eye wall is where
the most violent weather exists with a hurricane. The heaviest rain rates and strongest winds occur here.
Think of the eye as an invisible column of air in a tube with the clouds of the hurricane circulating around this tube. The low pressure of the hurricane is
'sucking' in air at the surface, and rising just outside of this tube in the eye wall. This rising air helps to form and organize all of the strongest storms in the eye wall by forcing
air upward. This pushes all this warm & moist surface air aloft. At an elevation of about 8 miles, the air temperature just outside of this eye or 'tube' can be as much as 18
degrees warmer than the air around it. This warm air then sinks down into the 'tube' into the eye. This causes the eye to clear out due to this sinking air or 'subsidence'.
The eye is where the lowest pressure of a hurricane exists.
Air rotates in a circular fashion into the storm, in a closed circulation fashion. The rotation of this air is counter-clockwise in the northern hemisphere and clockwise in
the southern hemisphere.
How Storms are Classified
There are 5 categories for hurricane classification, known as the Saffir-Simpson scale. The scale is named after the men who defined the scale; Herb Saffir, a wind engineer, and Bob
Simpson a meteorologist. The scale was designed to describe the damage done to buildings by hurricane force winds. It's important to note that the scale does not reflect the effects
of rain, flooding or storm surge. The scale ranges from 1 to 5; with 5 being the strongest.
A category 1 hurricane is classified when winds exceed 74 mph. Category 2 is with winds over 96 mph. A storm is considered a 'Major' hurricane when it reaches Category 3 or higher classification.
A Cat 3 has winds over 111 mph, Cat 4 over 130 mph, and Cat 5 over 157 mph.
Tropical Storm & Hurricane Names
In the early 1900s, an Australian weather forecaster named C. Wragge was the first man to give a hurricane a name.
Hurricanes & Tropical Storms are the only natural disasters that are given their own names, at least officially.
The Weather Channel in recent years has started unofficially naming storms themselves.
During the Tropical Disturbance -> Tropical Depression -> Tropical Storm -> Hurricane transition, the storm is only given a name once it becomes a Tropical Storm. That name continues
with the system during its lifecycle to a hurricane (if it becomes a hurricane), and even when it weakens back down to a tropical storm. Naming the storm is easier to identify
a system than to reference it by latitude/longitude coordinates. I'd rather call it 'Larry' than "20.3564, -40.6463".
There are six lists of storm names that are used in alphabetical order. The lists are reused every 6 years and is maintained and defined by an international committee of the
World Meteorological Organization (WMO). If a storm produces enough damage, a name can be retired and replaced with another name, never to be used again.
North Atlantic Names|
Eastern North Pacific Names|
The 2020 Hurricane Forecast
According to NOAA's Climate Prediction Center, an above normal hurricane season can be expected in 2020. They are expecting an above normal season with 13 to 19 named storms.
Of those 6 to 10 could become hurricanes with 3 to 6 of those becoming major hurricanes. They say that a normal season produces 12 named storms, 6 hurricanes and 3 of them being
major hurricanes. Typically El Nino can supress hurricane activity, however they are not anticipating an El Nino this season. Also ocean temperatures are running above normal. These
factors (and others) will contribute to the higher than normal activity, and NOAA says their forecast comes with 70% confidence. You can read the official press release at:
To the left: All tropical storm tracks between 1851-2017 in the Atlantic and 1949-2017 in the Pacific from the National Hurricane Center | View Large
Current Tropical Activity
Here is the current tropical storm activity, provided by F5Weather
Frequently Asked Questions (FAQ) & Facts
- A typical hurricane can easily drop 6 to 12 inches of rain, or more, over an area.
- The most violent part of a hurricane is in the eyewall. Here is where the strongest winds and heaviest rains occur.
- A large hurricane can release the equivalent energy of 10 atom bombs every second.
- Hurricanes and tropical storms can produce many tornadoes, although they are typically brief and weaker than tornadoes from a supercell.
- Most deaths from hurricanes come from the storm surge; a wall of rising sea water that innundates coastal areas.
- Hurricanes, as they are called in the North Atlantic Ocean, Central & Eastern North Pacific, are typically called Typhoons in the Western Pacific and Tropical Cyclones in the Indian Ocean.
- The planet Jupiter has had an ongoing hurricane for over 300 years. That hurricane is larger than all of Earth.
- Most hurricane eyes are 20-40 miles in diameter.
- A normal Atlantic hurricane season has 12 storms; 6 of those becoming hurricanes, 2 being 'major' category 3+ hurricanes.
- The most active season was in 2005 with 28 named storms, 15 of which were hurricanes. They actually ran out of storm names, and the last 6 storms had to be named Alpha, Beta, etc.
- 1983 was the slowest seson with only 4 named storms.
- Major hurricanes can have winds over 180 mph with gusts over 200 mph.
- The Great Galveston Hurricane of 1900 was the deadliest hurricane in US history killing somewhere between 8,000 and 12,000 people.
- The strongest North Atlantic hurricane by pressure was Hurricane Wilma in 2005, which had pressure down to 882mb.
- The strongest North Atlantic hurricane by wind speed was Hurricane Allen in 1980, which had peak sustained wind speeds of 190 mph.
- Since 1924, there have only been 5 storms hitting at Category 5 strength at landfall in the US: 1928 San Filipe II, 1935 Labor Day Hurricane, 1969 Camille, 1992 Andrew & 2018 Michael
- The largest hurricane in size was Typhoon Tip; a Category 5 Super Typhoon in 1979. It had a diameter of 2,220km or 1,379 miles and reached winds of 190 mph.
- Super Typhoon Tip was also the World's strongest hurricane by pressure; dipping down to 870mb in 1979.
- The strongest hurricane in the World by wind speed was Patricia in the Eastern Pacific in 2015. Patricia peaked at sustained winds of 215 mph.
Resources & Further Reading
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