Nov 2017

Hurricanes, Cyclones & Typhoons: Updated 2020

By Roya Eshragh

The tropics: the latitudes we associate with paradise. The term conjures up visions of holidays of yore. With those cerulean waters punctuated with occasional forest green land, bikini-clad tanned bodies on sunbeds with some type of frozen drink nearby. These are the areas you find hard coral reefs and charismatic megafauna, where liveaboards, snowbirds, and steel drums prevail.

But as I sat on one of those liveaboard boats, listening to the wind gusts of my third hurricane in as many weeks (Irma, Jose, and Maria), I couldn’t stop thinking about how the same warmth allowing me to dive without an exposure suit was wreaking some major havoc on my tropical home via the storms it created. It is indeed the price we pay for living in paradise. A price inflating exponentially every year thanks to changes in climates and rising water temperatures.

Last year (2019), the Atlantic saw 18 storms causing 116 fatalities! Tropical storms can form in any ocean, usually between 5 and 23 degrees and of the equator. The nomenclature can trip people up, but as with most things, it all comes down to location, location, location. In the Atlantic and the Northeast Pacific (Near the Americas), the storms are called hurricanes. In the northeastern Pacific, typhoons form; meanwhile cyclones rage in the south Pacific or the Indian Ocean. Appellations and locations are where these concrete difference end, however, as each storm is unique, but contains overarching characteristics similar to all its storm brethren.

How is a Storm Formed?

These storms form over warm water, where the heat causes the air to rise, creating a low-pressure area. This causes surrounding air from relatively higher pressure to push into the lower pressure centre. This new air then warms and rises just like the original air and so on and so forth. This convection, mixed with the Coriolis effect causes the storm to spin (clockwise in the Southern Hemisphere, counterclockwise in the Northern).

Meanwhile, the rising air cools as it reaches higher points in the atmosphere and forms clouds. These clouds now spin and cycle with the whole system as the air rises and falls in a circular manner. The very centre, where the air is heating and rising is called the eye. Usually, this area is very calm and can be up to 80km wide, but the circulating wind surrounds it is incredibly tumultuous. Because the eye is filled with low pressure, higher pressure air from above flows down into the eye, feeding the circulating air forces and increasing strength of “eyewall” which is the windiest part of the storm.


Those forming clouds hold a ton of water that condenses and falls as pelting rain over the diameter of the storm, which could be upwards of 2000km. This rain added to the storm surges of the sea is what tend to cause the most long-term damage by washing out whole river basins and flooding entire cities.

Hurricane Scales

According to the Saffir-Simpson scale of hurricanes, storms start as Tropical Depressions and move into Tropical Storms. As the storm gathers strength, and the winds reach a minimum of 30 knots (35mph, 56km/hr) of winds sustained for 10 minutes, it becomes a Category 1 hurricane. These don’t usually do too much damage to permanent structures, but can cause coastal flooding and power outages.

At 73 knots (84mph, 135 km/hr), the hurricane is updated to a Category 2, and a Category 3 at 84 knots (97mph, 156 km/hr). Category 3 storms are described as major hurricanes and can cause major damage to homes and trees. Flooding can be substantial and well inland. Infrastructure can be devastated, contaminating water supplies, and power losses are likely to occur for weeks.

A Category 4 Hurricane is achieved at 99 knots (114 mph, 183 km/hr) of 10 minutes of sustained winds. These storms cause irreparable damage to houses, gas stations, trees, and coastal systems. It can cause extensive erosion and flooding far inland.

Anything over 120 knots (140 mph, 220 km/hr) sustained winds is a Category 5, the highest category. As we’ve seen this year, Category 5 hurricanes cause mass devastation where they cross. Virtually all trees are uprooted and very few buildings can withstand the forces. Floods can completely wipe out even inland areas. Entire islands can be decimated beyond recognition. No Category 5 hurricane has yet made landfall in the Eastern Pacific basin, but they are becoming more frequent on the Atlantic side.

Changes in Climate

Because hurricanes form over warm water, they are becoming both more frequent and more intense. Scientists have been warning for years that the strongest storms are getting stronger. Global ocean temperatures in tropical storm areas had risen an average of 0.3 degrees Celsius (0.54 degrees Fahrenheit) from 1981 to 2006. The average wind speed also increased by 26 km/hr (16.1 mph) during that time.

The 2017 season broke records for all the wrong reasons, and climate scientists predict it will only be the beginning. In April this year, Tropical Storm Arlene began the third consecutive year with pre-season storms. June 1st is the start of the official season and was soon followed by Tropical Storm Bret, which hit the low latitude and thus rarely-struck Trinidad. From there, 2017 because the first season to have three storms Category 4 or higher to hit the US, and the first since 2005 to have four make landfall in the US. Hurricane Irma was the strongest storm to ever form in the Atlantic, and there was talk of creating a new category for her, moving up to a Category 6 hurricane.

Hurricane Irma passes Cuba and approaches southern Florida on Sunday, Sept. 10, 2017, in a NASA satellite captured a night-time image of the storm in the Florida Straits and identified where the strongest storms were occurring within Irma’s structure. NOAA’s GOES-East satellite provided a visible image at the time of Irma’s landfall in the Florida Keys. NASA photo

The season does not end until November 30th, but thus far there have been 16 storms, 10 of which formed into hurricanes. Of those, 6 became major hurricanes, resulting in 428 deaths and over 188 billion dollars in damage (USD). In fact, five of the ten most expensive storms in US history have all occurred since 1990. In the Pacific this year, there were 30 storms, 9 hurricanes, 9 typhoons, 4 major hurricanes and 2 super typhoons and 294 deaths and over $4 billion in damages. The Indian Ocean saw 2 cyclones with one being a Severe cyclonic storm, killing 395 people and causing $3.8 billion in damage.

These trends are only increasing, and all the warning signs say that storms will continue to strengthen, kill more, and cause more devastation. The argument of changing to renewable energy being too costly is quickly becoming too thin to hold the massive water these storms are dumping upon us.

‘Hurricanes, Cyclones, & Typhoons’ was written by Roya

Photo credit: Nasa, Wikipedia,

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Roya Eshragh

Even as a little girl, I was obsessed with the oceans and wanted to become a marine biologist. So, I got into diving in 2011 as an aide for my Master’s research on cephalopod (squid, cuttlefish, octopus, etc) parasites. I completed my PADI Open Water course and continued with the CAUS Scientific Diver course in the cold cold waters around Vancouver BC. When time allowed, I would help with the Howe Sound Research Group of the Vancouver Aquarium monitoring the Sound. I’m sorry to say, but even after all that, I still haven’t quite come to love dry suit diving.

Once I moved to Madagascar as the Science Officer of a marine conservation NGO, I realized just how lovely diving in the tropics could be. There, I completed my DiveMaster and became addicted to daily diving. I had to find a way to continue! So I did my IDC in Bunaken, Indonesia, completing my MSDT course and learning the tricks of the trade on a few inaugural students.

Currently, I am a dive manager/reef ecologist in Sri Lanka and starting up a conservation and education program with my dive shop. Combining my love of the oceans with my love of science, I am thrilled to have found a way to bridge the two and teach others about this incredible ecosystem we still don’t know nearly enough about. There’s still lots more for me to learn, both about diving and about the marine world, and that is the beauty of it all!

PADI Specialty Instructor
CAUS Scientific Diver 1
Master of Science - Zoology

Dream Dive Locations:
Komodo, Indonesia
Silfra, Iceland
Wreck Diving, Lake Michigan

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