The eye of the butterfly
Ocean Navigator|September - October 2020
The difference between the tropical cyclone and mid-latitude cyclone
JIM AUSTIN
The eye of the butterfly

June’s arrival marked two significant weather periods, the beginning of “summer” and the June-November hurricane season, both raising the possibility of stormy weather and the more important question: What kind of storm? Nightly TV predictions of fronts, winds and rain — weather typical of the mid-latitudes — are increasingly appended by “what the tropics are doing,” with an eye kept on disturbances and depressions in the Atlantic, especially the belt between 5° N and 20° N that can include tropical misbehavior. So, let’s a look at both, starting with the tropics.

Senegal’s Cape Verde (Cap-Vert) is a peninsula at Dakar jutting into the North Atlantic at about 14.7° N by 17.5° W, claiming priority as the westernmost point of the mainland African continent.

(Note that “Cape Verde” also applies to the independent island nation about 370 nm slightly northwest of its continental namesake.) Historically, Cape Verde has been associated with about 80 to 85 percent of the more destructive hurricanes (Category 3 to 5) that strike westward to the Antilles, the Gulf, Caribbean and U.S. East Coast, with September to October being statistically the most active period. But why would this African cape have such an outsized influence?

Imagine a rectangle, its west flank running from Florida southeast to the Lesser Antilles, crossing the North Atlantic, with its eastern flank not at Cape Verde but 2,500 miles further east across Africa to the Darfur Mountains and Ethiopian Highlands, their meridional ends linked by latitudes of about 5° N to 20° N. The trade winds flow west, prompted by Saharan hot, dry air to the north and warm, moist air from the Gulf of Guinea to the south; the African easterly jet results from this north vs. south contrast of temperature and density.

This story is from the September - October 2020 edition of Ocean Navigator.

Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 8,500+ magazines and newspapers.

This story is from the September - October 2020 edition of Ocean Navigator.

Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 8,500+ magazines and newspapers.

MORE STORIES FROM OCEAN NAVIGATORView All
Stay Connected
Ocean Navigator

Stay Connected

Satellite phones have evolved a full ecosystem of gear and services

time-read
9 mins  |
July - August 2021
Respecting Paradise
Ocean Navigator

Respecting Paradise

Thoughts on voyaging responsibly

time-read
6 mins  |
July - August 2021
Yankee sails on
Ocean Navigator

Yankee sails on

The steel ketch Yankee in the Connecticut River.

time-read
3 mins  |
July - August 2021
TRANSPAC RACE PREP
Ocean Navigator

TRANSPAC RACE PREP

How a group of determined mostly military veterans built a race team

time-read
7 mins  |
July - August 2021
NOAA upgrades its global weather model
Ocean Navigator

NOAA upgrades its global weather model

More data and a better global weather model should make for improved weather distributed to users, like this temperature gradient map.

time-read
3 mins  |
July - August 2021
From North Sea fishing to Sea of Cortez voyaging
Ocean Navigator

From North Sea fishing to Sea of Cortez voyaging

The former Dutch fishing vessel turned power voyaging yacht Varnebank in Mexican waters.

time-read
4 mins  |
July - August 2021
Chatter Chartroom
Ocean Navigator

Chatter Chartroom

IN 2019, MY HUSBAND, DOUG PASNIK, AND I RACED OUR first Transpac together with a team of 10 on our Andrews 70, Trader, comprised primarily of military veterans (see story on page 22). This year we are doing the race again and inviting four mentees from The Magenta Project to race with us.

time-read
7 mins  |
July - August 2021
Doing it all with one screen
Ocean Navigator

Doing it all with one screen

The steering station on this Gunboat cat is equipped with large-screen B&G Zeus MFDs.

time-read
8 mins  |
May - June 2021
Don't scrimp when it comes to the crimp
Ocean Navigator

Don't scrimp when it comes to the crimp

Solid crimp connections make your power voyager’s electrical system more reliable.

time-read
5 mins  |
May - June 2021
Chartroom Chatter
Ocean Navigator

Chartroom Chatter

Maritime Publishing acquires Ocean Navigator

time-read
7 mins  |
May - June 2021