WEATHER NEWS: Explaining nearly a week of unusually cold, wet weather in the Mid-Atlantic

Here is a recap of the week’s stormy conditions:

Hurricane Ian spawned a nor’easter that’s flooding the Mid-Atlantic coast

Hurricane Ian was initially lifted north by a dip in the jet stream. While the dip was enough to cause landfall in Florida and the Southeast, it was not enough to grab the storm and send it into the north Atlantic to die down.

Instead, blocking high pressure to the north, and a jet stream that went into hiding, allowed Ian’s vortex to stall in the Mid-Atlantic. As it did so, a new coastal low developed, feeding the region with more chilly air and rain for days on end.

The prolonged storminess also set up a long fetch of northeast winds, which fed the coastal flooding risk.

Ian’s remnants torment the coast

The mix of Ian and the coastal storm it spawned brought heavy rain and major coastal flooding.

While the tides did not rise as high as forecast in coastal Virginia, and historic flooding was not observed, there was minor-to-moderate damage. Tidal gauges along the Atlantic Ocean climbed just below moderate flood stage, with a gauge near the Chesapeake Bay Bridge-Tunnel exceeding its moderate flood stage marker.

Across Virginia’s Hampton Roads area, widespread coastal flooding prompted some schools to close or delay early in the week. It caused some minor damage to a fishing pier at Hampton’s Buckroe Beach, and gusty winds from Ian’s remnants blew feet of sand onto beach access walkways and onto the boardwalk, forcing crews to make repairs.

Drifting sand was also a problem farther north, climbing to the doorsteps of businesses along the popular boardwalk in Ocean City, Md. In New Jersey, onshore winds caused minor coastal flooding in seaside towns like Stone Harbor and Avalon.

In Atlantic City, sirens were triggered Tuesday to warn residents of rising waters along the coast. The storm left behind by Ian triggered several rounds of moderate coastal flooding in the area, causing minor damage and significant beach erosion.

The heaviest rainfall was reported in the New Jersey area. More than 5 inches of rain has fallen at the National Weather Service’s office in Mount Holly since Friday, the office tweeted. On Sunday alone, Atlantic City picked up just over 3 inches of rain. a daily record. Since Friday, the city has seen 5.85 inches of rain.

Over the past five days, a widespread 6 to 10 inches fell along the Jersey Shore. The rainfall jackpot appears to have been Barnegat Township, N.J., where one gauge tallied 11.94 inches of rain.

In the Virginia Beach area, on-and-off wetness over the past five days led to widespread totals of 3 to 5 inches.

Onshore flow from the coastal storm also brought unusually chilly October weather to the Mid-Atlantic. Temperatures in Allentown, Pa., did not climb above 50 degrees Fahrenheit on Tuesday, 2 degrees cooler than the old record, which was set in 2010. Allentown also saw a daily record rainfall total of 2.08 inches.

Salisbury, Md., also saw its coldest high-temperature record lowered from 56 to a brisk 52, while in Norfolk, the temperature on Tuesday could only manage to rise to 54 degrees, breaking the old record low maximum temperature of 58, set all the way back in 1974.

It has been among the top 10 coldest starts to October in and around D.C., as well as much of the East Coast in the wake of Hurricane Ian.

Both D.C. and Dulles set record low maximums for Oct. 4 on Tuesday — it was the first cool side temperature record of 2022 in the city. In Washington, the 55-degree high bested 56 in 1998. Records for the city go back to 1872. Dulles also reached 55, beating 56 in 2010. Dulles records go back to 1963.

During the five of six days with rain, from Sept. 30-Oct. 4, the average temperature ran 9.7 degrees below normal in Washington. On the coldest day of the streak, the record low maximum temperature was 19 degrees below normal for the date.

According to a climate perspectives tool from the Southeast Regional Climate Center, the weather in D.C. over the past week has been more like that in Eureka, Calif., and Seattle.

Although the rain has been consistent, it has not been too heavy most of the time. Unlike recent episodes of rain, flooding was nonexistent locally.

In D.C., 1.95 inches fell during the five days ending Tuesday. Wednesday’s tally will push the city past 2 inches for the six-day stretch. Baltimore, as measured at BWI, picked up 3.48 inches over the five-day stretch ending Tuesday, with a little more on Wednesday.

Six days in a row with measurable rain (0.01 inch or greater) is not too common in the area, although it happens on average about once or twice a year. The last time it happened before this past week was in late December 2021 to early January 2022.

That is only part of the story, though, since the city received considerably more than 0.01 inches each day. In fact, it was at least 0.17 inches or greater for five days straight. At that level of rainfall, the five-day run comes in at a tie for the sixth-longest such streak on record, with a maximum of seven such days during the wettest year on record in 2018.

The five-day rainfall streak ending Tuesday in Baltimore was even more impressive. The lowest level of rain of the stretch was 0.23 inches. Five days at or above that value was good enough for a tie for the third longest on record, back to at least 1871.

With rainfall finally coming to an end, and the storm system moving off, temperatures across the Mid-Atlantic should warm back into the 70s — with widespread sunshine — on Thursday.