The coming winter has been tough to forecast because the typical signs that meteorologists monitor to make a projection are absent.
Nonetheless, later this month, the National Weather Service will issue its official forecast for winter.
Don't expect anything earth-shaking. The agency is already saying that the odds of winter turning out any particular way are no better than a coin toss.
That's not always the case. Sometimes the weather service is able to project that the odds favor warmer or colder, snowier or drier, in different areas of the United States.
The reason for uncertainty is that the best-understood, longest-lived determinant of seasonal variation is in a sort of sleeper mode. Equatorial Pacific Ocean temperatures significantly influence winter when they're warmer or cooler than normal.
When the water temperatures are “normal,” then scientists don't have that reliable guidepost. More important, the lack of a powerful Pacific influence opens the door to other short-term or less-understood factors to assert themselves.
This year, the equatorial Pacific temperatures are about normal.
For a better understanding of how the National Weather Service develops a winter forecast, see a primer compiled by the Valley office of the weather service.