Hurricanes, North & South

Whats the farthest North and South a hurricane has ever landed? Has one ever reached Canada? As for south, Brazil?

Would you regard hurricanes and cyclones as being essentially the same thing? You can get cyclones on a large part of the east coast of Australia.

The 1938 New England hurricane delivered heavy rains and some wind to Montreal, even after crossing New England.

Tropical storms which do not make landfall regularly cross the Atlantic and impact Great Britain, though by that time they have diminished to just normal low-pressure storm systems as opposed to the much larger and more powerful things they are in the Antilles and southern U.S. There was an account of one (details not available, but well back in time) that was noticeable bad weather even after having passed up the Baltic and hitting St. Petersburg, Russia.

Hurricanes in Canada

Hurricane Hazel

And earlier this year:

Hurricane Juan hit the Atlantic provinces last year, and earlier this year a rare hurricane hit South America.

Hurricane Gloria in 1985 hit New England and Quebec, but that’s the most recent one in this area that I remember. Info here. Usually hurricanes that hit the US east coast turn east out into the ocean at or before Cape Hatteras.

Here’s Hurricane Luis (#12) which slipped over the end of Canada at about 48 degrees north.

Many hurricanes go up to the Canadien Maritime provinces and then head eastward towards England, but as an extra-tropical cyclone. A few years ago, one hit England with hurricane-force winds, altho the storm technically was not a hurricane, since it lost its tropical characteristics. That didn’t provide any comfort to those on the receiving end. Whether tropical, extra-tropical, or completely baroclinic, the winds were just as strong with plenty of moisture from the Atlantic.

Tropical storms that originate in the North Atlantic (i.e., north of the Equator) do not go south of the Equator. Any tropical storms that occur in the South Atlantic must, by necessity, have originated there.

I think we’re saying much the same thing, though with different terminology – what started out as a tropical storm did cause stormy weather in England, whether or not it retained its “tropical storm” character.

For reasons I’d have to consult a professional meterologist or search the web to find out, tropical storms do not seem to form in the South Atlantic. But both North and South Pacific areas are breeding grounds for them – the Australian/Ennzedd “cyclones” are what Americans (Anglo and Hispano) call hurricanes. (Note that “cyclone” is also a Midwest term for tornado, though that seems to have declined, and is the technical name for any low-pressure system with closed isobars surrounding it, even if there are no serious storms associated with it.

IANAPM, but one of the factors in the explanation you are looking for, Polycarp, is the Inter Tropical Convergence Zone (ITCZ). There are two in the Atlantic, actually. One is north of the Equator, one is south. These are areas where the clashing prevailing trade wind patterns provide the circulation that helps develop tropical cyclones. The one in the North Atlantic varies and wanders about a bit, but it’s generally in an area where there is ample warm, open water available for the development of storms as they move westward. The Southern Atlantic ITCZ is a bit more compressed, and doesn’t have the available fetch of the Northern one. Here is a picof storm formation in the northern one in the Pacific.

I realized after posting that I implied that there are two separate and distinct ITCZ’s. What I meant to say is that the location that the ITCZ takes when North of the Equator is more favorable for cyclone development than the location it tends to occupy when it is south of the Equator. There is only one ITCZ, which “follows” the sun as it goes through it’s seasonal variations.

Parts of Britain get many such storms every year. It’s one of my personal niggles that people (mainly in the South) refuse to understand that ‘hurricane force’ doesn’t mean ‘hurricane’.

The ITCZ doesn’t explain the origin of all tropical cyclones. Both Gaston and Hermine originated between SC and Bermuda, well north of this zone. Many Atlantic storms develop in the GOM, again well north, as well as some around the Caribbean. Many in the Pacific arise near Mexico. It does appear that most that develop off Africa are at or near this zone, but it doesn’t explain the others. And those that arise near Africa do so mainly in late August and later. Doesn’t similar conditions occur in the South Atlantic and Pacific outside of the ITCZ, as it does in the north Atlantic and Pacific? Of course the seasons are reversed in the hemispheres and the SST’s in the Southern hemisphere may not be at the necessary 80-81 degrees at the same time of the year, but I don’t think a few miles would make that much of a difference. More than warm temperatures are necessary, of course, and I reckon that the waters around the equator are always at least that warm.

Of course the ITCZ doesn’t explain everything about tropical storm formation. It does strongly affect patterns that were mentioned: the relative lack of southern Atlantic hurricanes (with only one debatable example in recorded history) and the fact that North Atlantic storms rarely cross the Equator.

But even the examples you mention, Gaston and Hermine, owe their existence to storm centers formed in this area that moved off North Africa, across the Atlantic, and then up the Eastern Seaboard. Pretty standard path, in fact. They did not form just off the coast; they became named storms only when they reached this area. Gaston, for example, had been Tropical Depression #7 earlier, and had been noted as a tropical wave much earlier and farther out in the Atlantic.

Similar histories apply to many Gulf and Caribbean storms. Mitch, for instance, was a weak tropical wave off the Cape Verde Islands, mostly dissipated in a strong shear environment, and then re-generated once the shear abated and it moved into very warm water off Central America. The “seed” of Mitch was still that same system that had formed off North Africa.

Also, if you look at the photo I linked earlier, you can see the actual formation of storms in the ITCZ off the coast of Mexico. Eastern Pacific storms do owe their creation to the ITCZ, among other factors.

Admittedly, I screwed the pooch on my initial explanation, so this was unclear, but the ITCZ moves. In our winter, it is South of the Equator and generating storms there. That Brazilian “hurricane” formed in January, remember. It doesn’t move just a few miles, but hundreds of miles. From, say, approximately 15[sup]o[/sup]N latitude to a similar position in the Southern hemisphere.

Even though it does track the Sun, ITCZ is still an important factor in the relative paucity of Southern Atlantic hurricanes. Storms and other disturbed areas created by the ITCZ in the North Atlantic have much, much more time to develop while crossing from Africa to Central America.

There are many reasons why hurricanes do not form in the South Atlantic, with no one overriding reason.

  1. Small amount of real estate. The ocean basin itself is extremely small compared to the other ocean basins, so there is not a lot of room for storms to form, especially closer to the equator.

  2. Cold water. The west coast of Africa has a fairly significant cold ocean current, and it extends pretty far north. Since there isn’t much water near the equator for storms in the first place, cool water further hinders storms. Also, the southern hemisphere in general does not have warm enough water that is located as far south as in the northern hemisphere. In August, much of the northern Atlantic and western Pacific has sufficiently warm water as far north as 30 degrees, while the warm water in the southern hemisphere only extends to maybe 15-20 degrees (in all basins).

Combining the first two points, the amount of area that meets the warm water requirement for tropical systems in the South Atlantic is about the size of the Gulf of Mexico and the Caribbean Sea, during the warmest time of the year
3) Lack of the monsoon trough. The monsoon trough is what helps trigger most of the storms worldwide. It is also known as the ITCZ (mentioned above). I’m guessing that the relatively large amount of land south of the equator (between South America and Africa) disrupts the wind flow that we have in the other ocean basins.

  1. Finally, and I’m just guessing here, the fact that South America extends far enough north into the tropics, makes it a lot easier for polar air masses to travel further north. These mid-latitude cyclones then push into the Atlantic further equatorward than the northern hemisphere, possibly not giving the atmosphere time to develop. Also, since these systems move further north, a jet stream will also be located further north, meaning higher amounts of wind shear over the ocean basin, which is bad news for tropical storms.

The South Atlantic hurricane this year was not a hurricane that formed traditionally. It formed off a mid-latitude cyclone that stalled in some relatively warm water. These storms are known as hybrids, or subtropical storms, in that it is initially a mid-latitude system, but eventually they develop tropical characteristics. In the north Atlantic, they are relatively common, occurring usually maybe 1-2 times a year, usually in the October-November timeframes. They are rarer in the other basins. The most common area for subtropical storms in the world is near Hawaii (however there is virtually no risk of them developing into tropical systems there) in the winter months, where they are known as Kona lows.


This is just plain wrong. TD #7 (later known as Gaston) along with Hermine both formed off the SC coast. Before TD #7 was called a tropical depression, it was just a low pressure area sitting out there, about 100 miles from where I live, dumping occasional rains for several days, in a counter-clockwise fashion. For some reason, the meteorologists did not call it a TD until a few days after its formation. Moreover, if you check on the hurricanes and tropical cyclones formed early in the season, most of them form over the GOM or Caribbean, as I said before. Storms do not move off Africa until later in the season. In fact, Frances is one of the first ones. There were one or two earlier ones, but they meandered into the north region, never to be heard from again.