# Hurricanes **URL:** \ **Category:** Factual Questions\ **Created:** [August 20, 2000, 8:54pm UTC](https://boards.straightdope.com/t/hurricanes/30083 "2000-08-20T20:54:46Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 20, 2000, 8:54pm UTC](https://boards.straightdope.com/t/hurricanes/30083/1 "2000-08-20T20:54:46Z")
Living on the Atlantic coast, and with the height of the hurricane season approaching, I submit a question to the teeming millions, of whom quite a few have much to contribute, which has bothering me for years. A tropical storm is classified as a hurricane when its minimal sustained (one minute or more) winds reach 74 mph. My question is this: At that speed, does the eye form? Does a storm having sustained winds of 70 mph not have an eye, whereas one having sustained winds of 75mph does? A corollary question is what are the so-called “tropical characteristics” of a storm? We here in the SE always hear about storms losing their tropical characteristics. Do they wear Panama hats and smoke cigars? One of them, I think, is that the lowest pressure is always found at the center, while in continental storms, areas of lower pressure are scattered. Another, I think, is that the isobars are very concentrated. Well, they’d hae to be to produce the high winds, but is that a tropical characteric? ---
**Author:** ![AWB](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@AWB](https://boards.straightdope.com/u/AWB)\ **Post date:** [August 20, 2000, 10:53pm UTC](https://boards.straightdope.com/t/hurricanes/30083/2 "2000-08-20T22:53:14Z")
By Chad Palmer, USA TODAY Weather team > [@](#): > > - > > Hurricanes and other cyclones that form in the tropics during summer are very different from the extratropical storms that often form during winter even though both may produce very strong winds and possible flooding. The seven main differences between hurricanes and extratropical storms are: > [ul] > [li]Hurricanes and tropical systems have no fronts.[/li][li]Hurricane winds weaken with height[/li][li]The centers of hurricanes are warmer than their surroundings[/li][li]Hurricanes and tropical systems form under weak high-altitude winds.[/li][li]Air sinks at the center of a hurricane[/li][li]Hurricanes’ main energy source is the latent heat of condensation[/li][li]Hurricanes weaken rapidly over land[/li][/ul] > Tropical systems are classified into four categories according to its degree of organization and maximum sustained wind speed. > > Tropical disturbance, tropical wave: Unorganized mass of thunderstorms, very little, if any, organized wind circulation. > > Tropical depression: Has evidence of closed wind circulation around a center with sustained winds from 20-34 knots (23-39 mph). > > Tropical storm: Maximum sustained winds are from 35-64 knots (40-74 mph). The storm is named once it reaches tropical storm strength. > > Hurricane: Maximum sustained winds exceed 64 knots (74 mph). > > Hurricanes are classified into different categories according to the Saffir-Simpson scale. Hurricanes can also spawn severe weather such as tornadoes as they move inland. \* So it’s at the tropical depression stage that a storm form an eye, with winds at 23-39 mph. Tropical storms and hurricanes are just stronger (and have names). These depressions’/storms’/hurricanes’ energy source is the latent heat of condensation of the warm ocean water. Once they hit land, there is just very little of that type of energy to use to sustain the storm. This is their “tropical characteristic”, a storm powered by latent heat of condensation. ---
**Author:** ![whitetho](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whitetho/32/1059_2.png) [@whitetho](https://boards.straightdope.com/u/whitetho)\ **Post date:** [August 21, 2000, 10:10am UTC](https://boards.straightdope.com/t/hurricanes/30083/3 "2000-08-21T10:10:25Z")
From what I’ve seen from weather reports, the key is whether the air in the core of the storm is warm or not–warm means a tropical storm, cold means just a low pressure system. A storm can switch back and forth between the two classifications–a key characteristic I’ve seen commented on in weather reports is whether there are thunderstorms around the center of the low pressure, which is considered characteristic of a tropical storm. When the thunderstorms start to disappear from the center (usually because the sorm is going over land or cold water) they talk about the storm becoming “extra-tropical”, and in cases where the thunderstorms appear or reappear (usually when a low pressure center goes over warm water) they talk about it gaining or regaining tropical status. Also, as far as I know non-tropical storms, no matter how fierce, never form eyes. (In tropical storms, in general the stronger the storm the _smaller_ the eye). ---
**Author:** ![AWB](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@AWB](https://boards.straightdope.com/u/AWB)\ **Post date:** [August 21, 2000, 1:09pm UTC](https://boards.straightdope.com/t/hurricanes/30083/4 "2000-08-21T13:09:43Z")
Extra-tropical also refers to cyclonic storms that form outside of the tropics, often after hurricane season. Sometimes 3 weather fronts meet in such a way as to start a spinning system. These sometimes skim the Atlantic coast in such a way as to pull water from the ocean, then dump it on the land. Since these are spinning counter-clockwise, the winds acompanying the storms over land come from the northeast, giving the name Nor’easters. Living in the DC area, we get hit hard by a nor’easter about every 2-4 years. If it happens in the winter and there’s a cold front paralleling the coast, we get dumped on by 2-3 feet of snow. It’s kinda neat getting buried, until it comes time to dig out. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 21, 2000, 1:40pm UTC](https://boards.straightdope.com/t/hurricanes/30083/5 "2000-08-21T13:40:01Z")
Thanks to every one who answered my questions re tropical storms, especially to Chad Palmer (AWB), who gave me a very detailed and excellent explanation. According to AWB, the sine qua non of a tropical storm is that it is powered by latent heat of condensation. “Latent” in this context meaning, I gather, energy created without a temperature change. AWB states that that is the tropical characteristic, and gave 7 main differences berween hurricanes and extratropical storms. However, I hear the weathermen referring to a storm which has made it to the North Atlantic as losing its “tropical characteristics.” Plural. So although the latent heat of condensation is the sine qua non, it is only one of several tropical characteristics, which, I assume, are the 7 things that AWB mention. If that be the case, I cannot agree with tropical systems having no fronts as a tropical characteristic. These once tropical systems now near England, or Labrador, or somewhere in the N Atlantic have lost their tropical characteristics, but they still don’t have fronts, do they? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 21, 2000, 5:37pm UTC](https://boards.straightdope.com/t/hurricanes/30083/6 "2000-08-21T17:37:47Z")
I had thought that Nor’easters were the middle northern-latitude trade winds. They don’t necessarily carry storms, but in the New England area, they often do. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 21, 2000, 5:52pm UTC](https://boards.straightdope.com/t/hurricanes/30083/7 "2000-08-21T17:52:55Z")
> [@](#): > > \*Originally posted by Chronos \* > \*\*I had thought that Nor’easters were the middle northern-latitude trade winds. They don’t necessarily carry storms, but in the New England area, they often do. \*\* I never heard of “nor’easters” being used in that context, but always thought it meant just what AWB said it means: a low pressure area wherein in the NE quadrant the winds are out of the NE. These storms usually form around where I live, SC, and move Nly along the coast, strengthening as it gathers in the moist Atlantic air. By the time they reach New England, they are quite strong. They could also come the usual way, out of the west or northwest, but they would then not have as much moisture associated with them. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 21, 2000, 6:03pm UTC](https://boards.straightdope.com/t/hurricanes/30083/8 "2000-08-21T18:03:46Z")
\>\> Air sinks at the center of a hurricane Can somebody confirm this? I was under the impression that it was precisely the contrary that was true. That warm water heated the air above which tended to rise and created a low pressure point. Can someone explain if this explanation is not so, then how does a hurricane “work”? ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 21, 2000, 6:14pm UTC](https://boards.straightdope.com/t/hurricanes/30083/9 "2000-08-21T18:14:43Z")
As I understand it, and I am not a meteorologist (AWB is a meteorologist and can more intelligently reply), air does sink in the center, but rises around the sinking air. This is what creates the eye and the eye wall. The rising air finally reaches its acme and descends at the center. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 23, 2000, 2:21pm UTC](https://boards.straightdope.com/t/hurricanes/30083/10 "2000-08-23T14:21:30Z")
Second thoughts on Chrnos’ statement about Northereasters. He referred to the middle Atlantic latitutdes. He obviously was referring to the Trade Winds (in the “Horse Latitudes,” I believe they are called), which are just above the equator. This is something entirely different from the Northeasters that hit New England, which are storms with a lot of moisture from the Atlantic, as AWB pointed out. In fact, it is the Trade Winds that account for the fact that these tropical systems that develop off Africa move Easterly, I believe. AWB can straighten me out on this if I am wrong. I don’t agree entirely with AWB’s statement that extra-tropical systems are always systems that develop outside the Tropics. They could be systems, like Alberto will be within 12 hours from now, that were once tropical, but have lost their tropical characteristics.