Atlantic and Pacific hurricane tracks

Hurricane Lorenzo currently in the mid Atlantic is cited as the most intense hurricane east of 45 degrees West longitude in the historical record. It’s heading north and only The Azores is at possible risk, depending on how it tracks and how much energy it retains.

This is detailed in Category 4 Hurricane Lorenzo is the Most Intense Hurricane So Far East in the Atlantic Ocean on Record, but included in that report is a fascinating map of category 4 or greater hurricanes in the Atlantic recorded since 1950.

Nearly all hurricanes begin north of the equator. Some of them come from a relatively small area west of Africa, with many beginning in a narrow band several hundred kilometres north of the equator, heading west and often veering north.

 

Tracks of all Atlantic Basin Category 4 or stronger hurricanes from 1950 through 2017. Segments during which each hurricane was Category 4 or 5 is shown by the pink and purple line segments, respectively. The position of Lorenzo when it first reached Category 4 status is denoted by the dot and arrow. The location of Julia when it was a Category 4 hurricane in 2010 is also highlighted. (Note: 2018 tracks were unavailable in the online database as of the time of this article.)

(NOAA)

Even in the heart of hurricane season, tropical waves moving off the coast of western Africa usually take some time to mushroom into intense hurricanes.

This is often due to intrusions of dry air, known as Saharan air layers, moving off Africa’s Sahara Desert. Fledgling tropical disturbances need warm, moist air to intensify, so battling these intrusions can prevent intensification or even spell doom in the eastern Atlantic Ocean.

In Lorenzo’s case, that wasn’t a big problem.

A lack of shearing winds, typically warm ocean water and moist air allowed Lorenzo to rapidly intensify so far east.

Wikipedia shows more on this in Atlantic Hurricane:

File:Atlantic hurricane tracks.jpg

Tracks of North Atlantic tropical cyclones (1851–2012)

Most storms form in warm waters several hundred miles north of the equator near the Intertropical convergence zone from tropical waves. The Coriolis force is usually too weak to initiate sufficient rotation near the equator.

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, the origin of strong and long-lasting Cape Verde-type hurricanes. Systems may also strengthen over the Gulf Stream off the coast of the eastern United States, wherever water temperatures exceed 26.5 °C (79.7 °F).

Steering factors

Tropical cyclones are steered by the surrounding flow throughout the depth of the troposphere (the atmosphere from the surface to about eight miles (12 km) high)…Specifically, air flow around high pressure systems and toward low pressure areas influences hurricane tracks.

In the tropical latitudes, tropical storms and hurricanes generally move westward with a slight tendency toward the north, under the influence of the subtropical ridge, a high pressure system that usually extends east-west across the subtropics.

South of the subtropical ridge, surface easterly winds (blowing from east to west) prevail. If the subtropical ridge is weakened by an upper trough, a tropical cyclone may turn poleward and then recurve, or curve back toward the northeast into the main belt of the Westerlies. Poleward (north) of the subtropical ridge, westerly winds prevail and generally steer tropical cyclones that reach northern latitudes toward the east.

Eastern Pacific hurricanes show similar patterns.

File:Pacific hurricane tracks 1980-2005.jpg

Tracks of East Pacific tropical cyclones (1980–2005)

Most of these head out into uninhabited parts of the Pacific.

The North west Pacific has a lot of typhoon activity.

File:Pacific typhoon tracks 1980-2005.jpg

Tracks of all tropical cyclones in the northwestern Pacific Ocean between 1980 and 2005.
The vertical line to the right is the International Date Line.

Closer to home we are sometimes affected by South Pacific tropical cyclones.

Within the Southern Hemisphere there are officially three areas where tropical cyclones develop on a regular basis, these areas are the South-West Indian Ocean between Africa and 90°E, the Australian region between 90°E and 160°E and the South Pacific basin between 160°E and 120°W.

Within the basin, most tropical cyclones have their origins within the South Pacific Convergence Zone or within the Northern Australian monsoon trough, both of which form an extensive area of cloudiness and are dominant features of the season.

The ancient mariners of the South Seas who roamed the tropical Pacific before the arrival of the Europeans, knew of and feared the hurricanes of the South Pacific.

They were keen and accurate observers of nature with traditional myths and legends, reflecting their knowledge of these systems.

There are fewer and much more scattered tracks in our part of the Pacific.

Tracks of all tropical cyclones in the southwestern Pacific Ocean between 1980 and 2005

You can see the inactive equatorial band between the north and south Pacific tracking maps.

You can see north of Australia and north and south Indian ocean tracks here (this post has already become a lot longer than intended): Tropical cyclone basins

Heat in the ocean waters is a major factor in hurricanes. If as most science suggests our oceans have been absorbing an increasing amount of heat then there is a risk of more hurricanes, typhoons and cyclones, and they are at risk of being more intense.