El Nino chances dropping

Back in June forecasts saw an 80 percent probability that an El Nino would ripen in the tropical Pacific in fall and winter, when sea-surface temperatures would hold significantly above normal.

Now, the experts are not so sure. Today the Climate Prediction Center and the International Research Institute for Climate and Society bumped down the probability of El Nino conditions to 58 percent.

They say that even if one does develop, it would be weak.

In its monthly update, the Instituted, housed at Columbia University, said the Pacific is exhibiting "borderline" El Nino conditions, but the warming continues at a tepid pace.

Given that weather moves west to east, the interactions of the atmosphere and sea-surface temperatures over a continent-size patch of the tropical Pacific have significant impacts on weather thousands of miles away.

The strong upper-air westerlies generated during El Nino are known to have a dampening effect on the development of tropical storms in the Atlantic Basin, although this year hurricane-suppression needed no El Nino help.

El Nino conditions clearly exert some influence on winter in the Philadelphia region, although the outcomes of El Nino-influenced years have varied wildly.

Total seasonal snowfall in the 10 winters that coincided with a weak El Nino is near the 22-inch average, but snowfalls of 6 inches or more have occurred eight times in those winters,  notes Tony Gigi at the National Weather Service Office in Mount Holly.

We don't know what affects conditions in the  tropical Pacific will have on winter around here, but we will observe that the prospect of El Nino was a common theme in those outlooks that have called for a snowy one.