INFLUENCE OF HURRICANES ON NAVIGATION IN THE NORTH ATLANTIC - PowerPoint Presentation

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INFLUENCE OF HURRICANES ON NAVIGATION IN THE NORTH ATLANTIC

Nenad LederFaculty of Maritime Studies, Ruđera Boškovića 37, 21000 Split, Croatia, nenad.leder@pfst.hrZvonimir LušićFaculty of Maritime Studies, Ruđera Boškovića 37, 21000 Split, Croatia,zvonimir.lusic@pfst.hr

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OUTLINEINTRODUCTION

GENERAL HURRICANE CHARACTERISTICSOCEAN PHENOMENA CAUSED BY A HURRICANEHURRICANE FORECAST REGIONS AND CENTRESNAVIGATION AND STAY IN PORTSCONCLUSION 2

1. INTRODUCTION

FACTS ABOUT HURRICANES TODAYHurricanes are the most violent storms on Earth;

They form near the equator over warm ocean waters

;

Actually, the term hurricane is used only for the large storms that form over the Atlantic Ocean or eastern Pacific

Ocean

;The generic, scientific term for these storms, wherever they occur, is tropical cyclone;Other names they are given, depending on where in the world they are born, are typhoon, willy-willy, cyclone, severe tropical cyclone, or severe cyclonic storm. THE MAIN GOALS OF THE PAPER1. To show the devastating impact of tropical cyclones on navigation in the North Atlantic;2. To give seafarers a brief historical overview of the intensity and frequency of the strongest hurricanes and the catastrophic damage they caused to ships, both on the high seas and in ports;3. To present the procedure that seafarers must follow in order to avoid a hurricane.

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. GENERAL HURRICANE CHARACTERISTICS42.1 Genesis area, climatological tracks and frequencyTropical cyclones/storms frequently form in the warm waters of the Gulf of Mexico, the Caribbean Sea, and the tropical Atlantic Ocean as far east as the Cape Verde Islands (Fig. 1). 2.2 Space scale, intensity and structure

Typical tropical cyclones/hurricanes space scales are between 100 and 2000 km in diameter.Meteorologist measure hurricane’s strength based on the intensity of their sustained wind speeds and rate them using

Saffir

–Simpson hurricane wind scale

.

To be classified as a hurricane, a tropical cyclone must have

one-minute maximum sustained winds of at least 74 mph (33 m/s; 64 kn; 119 km/h) (Category 1). The highest classification in the scale, Category 5, consists of storms with sustained winds over 156 mph (70 m/s; 136 kn; 251 km/h).A list of the strongest hurricanes recorded in the Atlantic Ocean is shown in Table 1.Figure 1: Category 4 and 5 hurricane tracks from 1851-2016 in the East Atlantic ocean basin.Table 1. Strongest Atlantic hurricanes by peak sustained wind speeds.

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2.3 The formation and development of a tropical cycloneTropical cyclones are like engines that require warm, moist air as fuel. So the first ingredient needed for a tropical cyclone is warm ocean water. That is why tropical cyclones form only in tropical regions where the ocean is at least 26 °C for at least the top 50 meters below the surface.Meteorologists have divided the development of a tropical cyclone into four stages: tropical disturbance, tropical depression, tropical storm, and tropical cyclone.

2.4 Physical

structure

The wind field of a tropical cyclone may be divided into

three regions

(Figs. 2 and 3). First is a ring-shaped outer region, typically having an outer radius of about 160 km and an inner radius of about 30 to 50 km. Wind speeds attain their maximum value at the second region, the eyewall, which is typically 15 to 30 km from the centre of the storm. The eyewall in turn surrounds the interior region, called the eye, where wind speeds decrease rapidly and the air is often calm.Figure 2: Physical structure of the hurricane.Figure 3: Hurricane Alen in the Gulf of Mexico on August 8, 1980, Category 5.

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3. OCEAN PHENOMENA CAUSED BY A HURRICANEOnce generated and developed above the ocean surface, they produce:strong winds; huge waves;storm surge which causes flooding in the coastal

area;heavy

rainfall, tornadoes, and

rip currents

.

Hurricane Dorian (Fig.

3) is expected to bring potentially fatal storm surges of 5 to 7 metres. The winds are estimated to be between 260 km/h to 295 km/h, with peaks up to 360 km/h.Copernicus Marine Service product predicted up to 11.2 m significant wave heights. Hence observed maxima waves could be 20 m (Fig.4). Figure 3: Hurricane Dorian at peak intensity on September 1, 2019. Figure 4: Huge hurricane waves.

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4. HURRICANE FORECAST REGIONS AND CENTRESThe marine weather broadcast and radio facsimile weather maps are the most important tools for avoiding tropical cyclones.Tropical storms developing in the world’s ocean basins are tracked by various national weather services that have been designated Regional Specialized Meteorological Centres (RSMCs) by the World Meteorological Organization (WMO).Forecasters use a variety of observational information from satellites and aircraft to determine the current location and intensity of the storm (Fig. 5).

Figure

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:

Forecast of the path and intensity of the tropical storm Arthur on 18 May

2020

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85. NAVIGATION

AND STAY IN PORTSBecause the tropical cyclone spins and travels at the same time, it creates different wind conditions north and south of the storm’s track. If tropical cyclone is divided along the route at which it is passing, then we get 2 parts (semicircles) in the Northern Hemisphere:Right-hand semicircle (RHSC), which lies to the right of the observer, who faces along the route of the storm. It is dangerous semicircle, where the storm has the strongest winds and heavy seas. The most destructive section of the storm is in this semicircle, usually in the eyewall area to the right of the eye, known as the right-hand quadrant, northwest quadrant or danger quadrant (Fig.

6);Left-hand semicircle

(LHSC), which lies to the left of the observer, who faces along the route of the storm.

It is navigable semicircle

, where wind are weaker (Fig.

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).Figure 6: Navigation in tropical cyclone.

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6. CONCLUSIONHurricanes are the most violent storms on Earth;Meteorologist measure hurricane’s strength based on the intensity of their sustained wind speeds and rate them using

Saffir–Simpson hurricane wind scale;

To be classified as a hurricane, a tropical cyclone must have one-minute maximum sustained winds of at least 119 km/h (Category 1

)

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Hurricanes of Category 5 produce strong winds (up to 360 km/h), huge waves (more than 20 m), storm surge (more than 7 m) which causes flooding in the coastal

area;Navigation in such meteorological and oceanographic conditions requires knowledge and top skills from the seafarer;To avoid tropical cyclones/hurricanes, seafarers must first follow the marine forecast by various national weather services;For navigation within a tropical cyclone / hurricane as well as for staying in port, seafarers must follow the procedures specified in the maritime manuals.

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