Kevin Myatt is The Roanoke Times' weather columnist.

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By now, we are all too familiar with how the warm waters of the Atlantic get the air spinning and roaring. But the cold waters of the northern Pacific can do the same, and ultimately, that region has more overall impact on our yearly weather than the Atlantic.

While we've been transfixed on the Atlantic tropical season, it's getting more active in the northern Pacific. You probably notice an autumn chill in the air today. Nice to have crisp air from Canada instead of murky air from the Caribbean, huh?

Strong westerly winds aloft over the northern Pacific are beginning to take over more of North America's weather scene. They're helping drive colder air farther east and south, and also beginning to attack a ridge of high pressure in the western states that's kept it pretty warm and dry out that way.

In time, they'll knock chunks out of the ridge, maybe flatten it altogether. These westerly winds may begin crashing large storm systems into the coast of the Pacific Northwest and nearby Canada.

Sometimes these cold, windy storms spin with near hurricane force, hurling mighty gusts of wind and water into the rocky Pacific coast. Snow piles up by the feet in the coastal mountain ranges, then later in the Rockies.

The Pacific storms, after various incarnations in crossing the country, can become weather makers for us. They drag through cold fronts that can bring rain -- showers, thunderstorms or a day-long steady rain -- followed by those clear, cool autumn days that should make even the crustiest pessimists among us feel a tingle in their hearts.

Over the course of a year, we're affected by scores of storms off the Pacific, compared with just a handful of Atlantic-born tropical systems. Nearly every significant rain or snow-maker we get has at least some contribution from the Pacific.

None of what is going on now in the Pacific is unusual. The pattern varies some from year to year in its intensity and placement, but this is the annual march of seasons that will, not many weeks from now, have us speculating about winter storms rather than tropical ones.

he boundary between summer's warmth and winter's cold is shifting southward as the days in our hemisphere get shorter and the sun angle gets lower. It is along the boundary between warm and cold that the most vigorous weather occurs, whether atmospheric energy gets the most charged up.

One thing that happens in the cooler months is that we often have multiple branches of the jet stream to watch. The polar jet stream is one branch, and it's roaring hard and fast in Canada, though not diving down far enough south yet to bring in the hard-freeze cold to us yet.

It's important to watch this development the next few weeks, as the polar jet stream could bring frequent storms to Canada that build up snowpack. Canadian snowpack is important in holding in cold air masses that come down later in the season.

A southern jet stream often develops from the Pacific across northern Mexico or the southwestern United States eastward across the Gulf of Mexico. This can be our moisture train, the supplier of our rain, ice and snow.

There is only a hint of such a development now, but it's a bit early to expect it.

El Nino is still the player that hasn't really showed its hand yet.

Officially, sea surface temperatures in the equatorial Pacific have been warm enough over a 3-month period to declare that an El Nino has developed.

However, most of the warmth has been focused on the central and western Pacific rather than the eastern side closest to the Americas.

Should El Nino get firing more deeply and widely, it would likely invigorate the southern jet stream and more moisture-laden storms could develop.

Finally, don't take your eyes entirely off the tropics just yet. The chances have diminished for long-track hurricanes that form deep in the Atlantic and build for days before hitting the United States.

But there are still pockets of warm water with still air above. One such area to watch the next few days is the westen Gulf of Mexico, where a tropical low is expected to begin forming. If a tropical low gets scooped up by a Pacific low with a cold front, our tropical rains might not be over yet.