Kevin Myatt is The Roanoke Times' weather columnist.

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The coastal storm doesn't bear a name, but it has an attitude.

It's gone through a bit of an identity crisis. Is it a nor'easter? Is it tropical? Or some mix between the two?

The strong low pressure system has been battering the beaches of the Carolinas and southeast Virginia with wind and waves. On Thursday, it gradually pushed a shield of much-needed rain toward us. Rain will continue today into Saturday, with 1 to 2 inches in many areas.

The National Hurricane Center first wondered on Wednesday if this system might be turning into a tropical storm over the Gulf Stream's warm waters. A hurricane hunter aircraft found otherwise at the time, but the question still lingered on Thursday as the storm's center began to wrap up more tightly.

For now, unless something has changed overnight, we can just call it a strong low pressure system, a coastal storm, or a nor'easter. It's an academic point: Tropical or not, it means wind, waves and rain.

The difference between tropical and nontropical low pressure systems is more about mechanics and structure rather than strength.

Tropical systems and nontropical low pressure systems -- often called extratropical -- are different kinds of cyclones, or regions of rotating air being lifted upward. In the Northern Hemisphere, the Earth's rotation causes cyclones to rotate counterclockwise.

Tropical cyclones derive their energy from the latent heat released by evaporating ocean water. Tropical cyclones have a very tight, warm inner core, around which the rest of the storm circulates.

Extratropical cyclones derive their energy from a boundary between clashing air masses, usually cool, dry air on one side and warm, moist air on the other. When sufficient spin is present in the upper atmosphere, that spin can be transferred to the surface along a boundary between air masses, causing a surface low pressure system to form.

Extratropical cylones have a broader circulation than their cousins. In tropical cyclones, the strongest winds are usually in the eye wall 10 to 50 miles from the center of circulation. The strongest winds in extratropical cyclones can be hundreds of miles from the center.

Hurricane hunter aircraft examining the coastal low Wednesday found no tight central core, and the strongest winds were more than 100 miles from the storm center.

Tropical cyclones include everything from puny tropical depressions with winds below 30 mph to catastrophic Category 5 hurricanes with winds topping 155 mph.

Extratropical cyclones include everything from weak low pressure systems that are only discernible by a weak wind shift and a few clouds, to mighty tempests like the Superstorm of 1993, which spawned hurricane-force winds, a deadly tornado outbreak, a hurricanelike storm surge, and a massive blizzard in the Eastern U.S.

So each category of cyclone has a wide range of potential intensity. The strongest hurricanes have higher winds than the strongest extratropical cyclones, but even a large hurricane's wind field doesn't extend as widely as that of a very large and powerful extratropical cyclone.

Sometimes, a system will exhibit characteristics of both. This kind of hybrid system is called "subtropical." Often, these occur when the ocean water temperature is somewhat below the critical threshold of 80 degrees, or when a large extratropical system has one region within it that begins to take on a tropical structure.

There is still some chance that this coastal storm might become subtropical if not fully tropical. The National Hurricane Center does apply its naming convention to subtropical storms if their winds are 40 mph or greater. If it becomes a named storm, tropical or subtropical, it would be Laura. Tropical Storm Kyle formed east of the Bahamas on Thursday and will be deflected from the United States by the coastal storm.

The generic name commonly applied to a strong low pressure system on the East Coast is "nor'easter." That's because its rotation whips northeast winds into the coast as it goes by, often causing beach erosion by churning big waves and spreading wind-whipped rain or snow well inland.

We haven't seen a lot of nor'easters along the Southeast and Mid-Atlantic coasts in recent years.

Is the development of this nor'easter so far south and so early in the fall a sign that we'll see more of them this winter?