Region's 5-year wet streak hits a dry patch

Despite chronic storm threats and occasional drops of actual rain, a brown tide has crept across the region's landscape.

While that may signal the onset of a drought, the fact that the dryness has been so noticeable underscores a remarkable period in Philadelphia's weather history.

Very simply, we're not used to these brown-outs.

For the first half of the year, Philadelphia's precipitation was about two inches below normal, and if that trend continues, it will end an unprecedented wet streak.

Last year was Philadelphia's fifth straight with above-average rainfall, the first time that has happened in the 134 years of recordkeeping.

That's extraordinary, even though the Northeastern United States, close to the ocean and along busy storm tracks, is in one of the world's more-reliable rain belts.

While from 1980 to 2002 the Philadelphia region was in some state of drought 30 percent of the time, it has been more than six years since the last serious dry spell.

"This has been the anti-drought," said Gary Szatkowski, the meteorologist in charge of the National Weather Service office in Mount Holly.

That could be changing.

During the last several weeks, rainfall deficits have been growing subtly across parts of Pennsylvania and New Jersey. The results are evident to farmers. Some of them were shut out of their fields by mud during a rainy spring, and now they find that a drying sun is making hay a bumper crop.

"The grass is turning brown quickly, and crops are starting to show some drought stress," said Judy Behney of the Adams County Farm Services Agency, in the heart of Pennsylvania farm country.

"What we are seeing in the beginning of July is usually what we see in mid-August," said Christopher Palmer, operations and landscape management director of maintenance for Philadelphia's Fairmount Park system.

The hit-and-mostly-miss thunderstorms last week haven't been much help to the 9,200-acre park system's foliage, which is scattered from deep South Philadelphia to the Far Northeast.

Meteorologists attribute the dryness to an atmosphere that has been as capricious as a thunderstorm. In summer, when the sun's energy is spread most evenly across the Northern Hemisphere, the temperature contrasts that drive storm systems are weak, so rain tends to be less organized.

What is happening in Philadelphia could be simply a quirk. Fronts aplenty have passed through the region, but they have wrung out little more than rumbles of thunder and the sound and fury of scary weather watches. Last year, while Philadelphia was getting abundant summer rain, a drought devastated Washington, D.C.

The circumstances are quite different this year, as Philadelphia, rather than Washington, has been in the dry zone.

"You guys are just missing out because we're getting all the rain," said Michael Halpert, deputy director of the government's Climate Prediction Center outside Washington, where more than 19 inches - double the average - has fallen in the last 90 days.

Not that D.C. is getting all of it. The June totals in the flood-ravaged Midwest were staggering. More than a foot fell in northern Missouri in one week, and more than a foot was measured for the month in parts of Iowa, Illinois and Indiana, said Doug LeComte, senior meteorologist and drought specialist with the climate center.

He said he could not identify any dominant feature that is governing the nation's weather this summer, and the causes of the dryness around here remain a mystery.

For that matter, so do the causes of the prolonged wet period that may be ending.

Global warming is certainly a suspect; however, the evidence is conflicted.

Worldwide, precipitation has increased slightly in the last 100 years as temperatures have risen, but most of that increase occurred before 1950. While the last five years were wet in Philadelphia, they were not quite as wet as the 1975-79 period, which was interrupted by a dry 1976.

As for droughts, the region had a sequence of significant ones from 1980 to 2002, but they were not in the same league as the drought of the mid-1960s or a prolonged dry spell at the end of the 19th century.

LeComte said he was confident that Philadelphia was not quite ready to slip into drought. The long-range forecast calls for above-normal precipitation into mid-month.

And as dry as it seems, the deficits, only 10 to 15 percent below normal for the last 90 days, do not suggest aridity.

While the region is not showing up yet in the government's weekly drought advisories, Szatkowski said: "My lawn would argue differently."