Kevin Myatt is The Roanoke Times' weather columnist.

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El Nino is on.

Back on Aug. 16, I discussed the possibility of that development in this column, noting a broad area of slightly warmer-than-normal water in the equatorial Pacific. Within the past two weeks, the Climate Prediction Center has observed a rapid increase in this oceanic warming, and has declared an El Nino to be under way.

Coupled with the sea surface temperature observations, the Climate Prediction Center also noted in a statement it issued Wednesday that dry weather, relative to normal, has firmly established itself over parts of Southeast Asia, a common result of an El Nino pattern.

The statement also mentions that the developing El Nino may already be helping to weaken what was projected to be a much-above-normal Atlantic hurricane season. I've discussed that previously.

But while El Nino can have effects throughout many seasons, it is regarded primarily as a winter phenomenon, as exemplified by its name meaning "little boy" that ties it to the Christ child because it usually peaks near Christmas. So it is in the United States' winter season that we usually see the most direct effects from El Nino.

Those expectations include, generally speaking, wetter-than-normal conditions across the southern tier of the United States, drier-than-normal weather in the Ohio Valley and upper Midwest, and warmer-than-normal weather in the Pacific Northwest and northern Plains.

Everywhere else, there is more variation. At the National Weather Service town hall meeting held Tuesday at the Roanoke Civic Center, meteorologist Stephen Keighton noted, in answering a question about El Nino, that correlations between El Nino or its sister La Nina (abnormal cooling of Pacific waters) and winter weather in our area are fairly weak compared with some other areas'.

But he also noted, as I have in this column, that the intensifying of the southern jet stream during an El Nino can lead to more precipitation-bearing storms across the Southern states, and some of these can reach into Virginia and increase our winter precipitation.

Just to get a sense of what it might mean for us in a few months, I looked back at Roanoke's climate data for the 11 El Nino winters that have occurred since weather records began at Roanoke Regional Airport in 1948. I am calling December through March winter for the purposes of this cursory look, even though the official meteorological definition of winter leaves out March.

El Nino winters have been more likely to be wet than dry in Roanoke. Of the 11, seven were at least an inch above the long-term average (1948-2005) in precipitation for the four months I examined, and two others were very close to that average. Only two were significantly drier than average.

Temperatures were all over the place, but there was a slightly greater tendency for warmer-than-average weather. Of the 44 months examined, 18 had monthly average temperatures at least two degrees above the long-term average, while 14 had temperatures at least two degrees below average and the remaining 12 were within two degrees of average.

Snowfall was the biggest surprise to me.

El Nino winters here tend to be feast-or-famine in snowfall. Six of the 11 El Nino winters had snowfall of 28 inches or greater, which would be considered well above our long-term average near 21 inches.

Our record snowy month, 41.2 inches in January 1966, happened in an El Nino winter. The snowiest winter of the snow-starved 1950s (28.30 inches in 1957-58), the snowiest winter in the snow-blessed 1970s (37.3 inches in 1977-78) and the snowiest winter so far in the relatively snow-deficient 2000s (29 inches in 2002-03) have been during El Ninos. A massive February 1983 snowstorm that left 1 to 2 feet across our area, on the way to a 35-inch season, also occurred in an El Nino.

On the flip side, four of the other five El Nino winters featured snowfall below a foot for the entire season.

So what can one confidently deduce from this information? The only thing I'd be comfortable in saying is that our winter is more likely to be wet than dry during an El Nino. We'll have to observe other factors to determine if it's warm or cold, and whether any extra moisture El Nino throws our way will be more rain or snow.

We still have more than two months to try to figure that out.