Philly matches a 125-year-old record for dryness, and the rainless streak continues

With 100% of the precincts reporting, Philadelphia has matched a record for dryness that dates to 1874 and the dawn of official weather recordkeeping in the United States.

Sunday was the 29th consecutive day without measurable precipitation in Philadelphia, and forecasters say that in all likelihood, the streak will reach at least 31. Take that, 1874!

In addition, by the time a balmy Halloween comes to an end, forecasters are confident that the city officially will have experienced the driest month — not just the driest October — on record.

So far the only blemish on a 29-day run of pure 0.00 totals was the “T” for trace during the early morning darkness of Thursday. By definition, a droplet of rain detected by the automated or paid human observer at Philadelphia International Airport qualifies as a trace. To qualify as “measurable,” the total must reach at least 0.01 inches.

After what the chilliest morning of the season Monday — with readings in the upper 20s just outside the city , a front approaching on what may be a near-record warm Halloween could touch off something on the order of a whole 0.01 or 0.02 inch of rain, said Ryan Abramson, a meteorologist with AccuWeather Inc. However, forecasters expect that deluge to hold off until Friday morning.

October is one of the year’s driest months because it typically lacks both the downpours of summer thunderstorms and the heavy rains of the more organized storms driven by the temperature contrasts of late fall and winter, said AccuWeather senior meteorologist Dave Dombek.

In some years, tropical storm remnants come to the rescue, but that hasn’t been the case this year. If anything, the tropical storms that have affected the South have conspired to help deprive the Philly region of rain.

Weather service meteorologists say that the heavy, sinking air associated with high pressure that has cut off moisture from the Philly region in part has been a response to the rain-bearing rising air associated with those storms. Nothing happens in a vacuum in the atmosphere.

Several fronts have crossed the region, but they have been about as dry as the dirt paths around here.

High pressure has dominated the weather agenda in Philadelphia and in much of the East for weeks, and “it kind of looks like it’s going to remain that way,” Frank Pereira, a senior branch forecaster at the government’s Weather Prediction Center in College Park, Md., said last week.

Not yet.

While New Jersey has declared a drought watch and is asking residents to conserve water, Pennsylvania has been holding its fire, even though the intergovernmental U.S. Drought Monitor map, produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, has much of the region in “severe drought” conditions.

Water supplies evidently haven’t reached critical shortages. Plus, meteorologists note with the foliage about to call it a year and no longer needing the watering it required during the spring and summer, an October dry spell isn’t in a league with one in, say, June.

Plus, despite the recent record dryness, in the 365-day period that ended Friday, all eight counties in the Philly region have received precipitation at near or slightly above normal levels, according to the weather service’s Middle Atlantic River Forecast Center. The center uses a sampling of stations to calculate county-wide totals.

The region has not experienced a serious drought in over 20 years, according to Pennsylvania Department of Environmental Protection data.

Aside from those possible sprinkles Friday morning, the best shot for rain likely would be election week, said AccuWeather’s Bob Larson, as it appears that the upper air is due for a pattern change.

That front approaching Thursday likely will have a benign effect on trick-or-treaters.

The warming winds out ahead of the front may send temperatures toward 80. The record for the date is 82, set in 1946.

And while in recent days the temperatures have dropped quickly as the sun wanes, winds from the southwest will keep in warmth after sunset.

“The temperatures will be more sluggish to drop off in the evening,” said Larson.

For a Halloween, not a scary forecast at all.