Winter could be snowiest on record

If the atmosphere could be checked for performance-enhancing substances, no one around here would be surprised if it tested positive this winter.

Something wild is going on. Two-foot snowstorms are rare around Philadelphia; two of them in one season, unprecedented.

And even before the workweek grime has a chance to settle on that magnificent snow pack, private and government meteorologists are warning of another major storm late tomorrow into Wednesday.

No one is guessing accumulations yet, but the computer models were showing scary-looking precipitation amounts, bulls-eyed right over our area, the National Weather Service said.

In short, it's at least possible that the all-time seasonal snow record, 65.5 inches, set in the winter of 1995-96, might not survive the week. With the official 28.5 from the weekend storm, Philadelphia sits at 56.3.

It's crazy, said Dean Iovino, a meteorologist at the weather service office in Mount Holly.

For reasons that elude the best minds in meteorology, the atmosphere is now caught in a rather fascinating rut. Juicy storms keep rippling just to our south, while cold air keeps holding its ground to the north.

Why the white madness?

The consensus is that the extra juice is being supplied by the continued warming of the equatorial Pacific, where the sea-surface temperatures are 2 to 4 degrees above their already tepid normals.

That toasts the air and has a profound effect on west-to-east upper-air winds across North America. It probably has a lot to do with the fact that Olympic organizers in Vancouver have been sweating bullets about the persistently un-wintry weather out their way, a common occurrence during El Niño.

Another reliable El Niño signal is storminess in the Southeastern United States, as El Niño energizes the southern storm track.

The strong El Niño of 1997-98, for example, was a winter nightmare for the Florida snowbirds. In February, a tornado outbreak killed more than 35 people not far from Disney World.

For the mid-Atlantic and Northeast, however, meteorologists have learned anew that no two El Niños are alike. Some years, the storms don't get up this way. In others, the El Niño winds rout the cold air. In the winter of 1997-98, Philadelphia had 0.7 inches of snow for the entire season.

This winter, the storms are getting close enough, and that atmospheric blocking pattern to the north has supplied sufficient cold air for snow. Not that it has been all cold here. Since Dec. 1, temperatures have been almost dead-on normal. It's just that the cold and the storms have been bonding.

That same cold, dry air to the north has been the friend of highway departments in New York and southern New England, and a curse for snow lovers. Albany's seasonal snow total stands at 21.5 inches; and how often does it happen that in the first week of February, Philadelphia's snowfall is almost double Boston's (28.9)?

One persistent feature of the pattern has been a swirling mass, or vortex, of upper-air winds over Nova Scotia that has kept storms from getting too far north, said Wes Junker, a former chief weather service meteorologist, now retired and living in the snowbound Washington area.

It's been in a very good position for us, said Junker, an expert on precipitation who is still active in the weather community.

Everyone agrees that major factors in the blocking have been the unusual and persistent high pressure patterns over the Arctic and North Atlantic. Both those patterns are tracked by indexes. When the pressures are higher to the north, the indexes are said to be negative, and cold air tends to pour into the Northeast. This season, those indexes have been, extraordinarily in some cases, historically negative.

That's a reversal of the positive trend that has dominated since the 1970s.

Asked if the general warming of the planet might have something to do with the extreme mid-Atlantic snowstorms, Junker averred. He said it would be unwise, if not irresponsible, to draw conclusions based on what happens in one winter in one part of the country.

While Philadelphia had never had two such mega-storms in a season in the period of record, those records date only to 1884 and track only the very modern period of the atmosphere. It could well happen again during the next 126 years.

In the near term, Junker believes, Philadelphia has an even better shot at significant snow this week than Washington, where a winter-storm watch was posted yesterday. It's looking like a surer thing in Philly, he said.

Alan Reppert, a meteorologist with AccuWeather Inc., concurred: It looks like we're going to see plowable snow.