Philly just set one weather record, and three more could fall this week

On the day after Philly set a record for the most consecutive days without rain, it appeared almost certain on Tuesday that this would become the driest October — and driest month, period — in a city with one of the oldest official weather databases in the country.

As a sweetener, it’s also possible that on what is expected to be a dry Halloween, the temperature will make a run at the warmest Oct. 31, an honor now held by 1946, when it went up to 82 degrees.

Given Thursday’s forecast high of 80, “We’re going to come close,” said Raymond Kruzdlo, a meteorologist at the National Weather Service office in Mount Holly. Kruzdlo also happens to be the office’s senior service hydrologist.

He is well aware that it has been a while between flood watches.

Monday marked the 30th straight day without measurable precipitation in Philadelphia, which began keeping records in 1872.

The previous record for consecutive days without precipitation in Philadelphia, 29, was set in 1874, not long after the nation’s weather service was created in 1870, a signature accomplishment of the Ulysses S. Grant administration.

(The Inquirer took note of the 1874 streak, which ended on Nov. 8, but only in passing. It appeared to devote more space to a six-week dry spell in Alabama.)

Philly did record a trace of rain Thursday, but it didn’t measure up to the 0.01 inches required to break the streak, which began Sept. 29.

New Jersey has declared a drought watch, a step Pennsylvania hasn’t yet taken.

The previous driest months on record in Philly — with a total of 0.09 inches of precipitation measured — occurred in 1963 and 1924. Not surprisingly, both were Octobers.

October is a transitional month for Philadelphia, between the showery summer and the steadier precipitation associated with more organized storms that come with nor’easters and cooler weather.

Prime sources of October rainfall have been tropical storm remnants and precocious nor’easters.

Neither source has materialized around here lately, and based on the forecasts, at 11:59 p.m. Thursday, this should become the first month on record in which Philly will have recorded no measurable precipitation. That, of course, would be a record for October.

The dryness of the air has contributed to the rapid cooling after sunset and for a series of chilly mornings.

On Monday, several areas outside the city recorded readings below freezing and even in the upper 20s, although urbanized heating helped keep temperatures above 40 at the heat-resistant Philadelphia International Airport. The weather service declared an end to the “growing season” in most of the region.

The aridity has resulted from persistent high pressure, or heavier air over the East, which has repelled rain with its descending currents. Air needs to rise for water vapor to condense into raindrops.

In effect, the Northeast has been cut off from the Gulf of Mexico, an important source of moisture.

The parched conditions also have contributed to the fact that when fronts have come through the region, they’ve been as dry as the dirt, meteorologists said.

Showers are at least possible Friday morning and perhaps very late Thursday night, said Michael Silva, weather service lead meteorologist.

And Kruzdlo said the pattern appears to be on the verge of relenting. High pressure is expected to back off during the weekend.

The government’s Climate Prediction Center has the odds slightly favoring above-normal precipitation during the Nov. 5-11 period.

The pattern is looking “more transient,” Kruzdlo said. He said that a system approaching the region next week may be able to mine some of that Gulf moisture.

But he does not expect to be issuing any flood advisories.

If the region does finally get some rain events, he said, “They don’t look like big shots.”