An intense storm with impacts that stretched across nearly 2,000 miles that included Connecticut was the result of a possible bomb cyclone whose moisture was fueled by an atmospheric river.
The storm moved in fast and is now leaving nearly as quickly, moving out across Quebec. In its wake, colder air is crashing in on gusty westerly winds, with wind chills dropping into the 20s.
The storm that developed rapidly along the coast on Wednesday brought wet and windy conditions to the Mid-Atlantic and Northeast, according to the National Weather Service. Winds gusted to nearly 70 mph along the Massachusetts coast and up to 40 mph in Hartford. Heavy rain also accompanied the storm, with many locations seeing their highest one-day totals in months.
The 1.42 inches of rain reported in Hartford was more than the total rainfall received there during all of September and October combined. Providence was soaked with 4.6 inches of rain yesterday, while Boston received 2.76 and Worcester had 1.96. Those amounts set a daily record for rainfall for all three locations for Wednesday.
At one point on Wednesday, more than 11 million people across New England were under a flood watch, according to the Iowa Environmental Mesonet. The storm also prompted high wind warnings and winter weather advisories for several million in the region and caused power outages and flight delays for airports along the coast.
The storm could qualify as a bomb cyclone, a classification given to a storm that intensifies rapidly over a 24-hour period. It needs to meet the criteria of a drop of at least 24 millibars in pressure over 24 hours to earn that recognition. Millibars are the units meteorologists use to measure pressure in the atmosphere.
The average sea-level pressure is around 1013.25 millibars. Storm systems at Connecticut's latitude have dropped to as low as 950 millibars.
A preliminary analysis of the storm from meteorologists with the Boston National Weather Service office on Thursday morning suggests the storm came close to being a bomb cyclone, dropping at least 21 mb in a 24-hour period. The central pressure of the storm as it moved into Canada dropped to 984 millibars.
According to the latest report for the U.S. Drought Monitor, the storm managed to squeeze out heavy rainfall in a region experiencing a widespread drought. The analysis from Dec. 5 revealed that more than 60% of the Northeast was in at least a moderate drought, level one out of four.
An atmospheric river helped supply the storm with abundant moisture.
"Atmospheric rivers are relatively long, narrow regions in the atmosphere -- like rivers in the sky -- that transport most of the water vapor outside of the tropics," according to the National Weather Service. "While atmospheric rivers can vary greatly in size and strength, the average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River."
The atmospheric river that fueled this week's storm brought moisture from the Gulf of Mexico and the southern Atlantic Ocean as far northward as New England. The water vapor that eventually fell as rain was carried over at least 1,200 miles.
On the warm side of the storm as it advanced toward the Northeast, powerful southerly winds ahead of the system yesterday pushed a storm surge to nearly 3 feet along the Massachusetts coastline.
The center of the intense system has moved out, but it is still impacting the region. The powerful circulation around the storm will unleash another round of bitterly cold Artic air and send it southward into the central and eastern portions of the United States.
Thursday and Friday, as the storm nudges northward through eastern Canada, Connecticut will be dealing with gusty westerly winds bringing in increasingly colder temperatures.
In the western and northern parts of the state, highs may fail to get above 40. Gusty winds will make it feel like the lower to middle 20s this afternoon. Lows will drop into the upper teens and lower 20s tonight, and highs tomorrow will top out near the freezing mark.
Parts of the state will experience some of the coldest air of the season so far Thursday night and Friday.
Arctic air carried by strong northwesterly winds will sweep across the relatively warmer waters of the Great Lakes and dump snow that will be measured in feet in some spots. Winds will gust to near 50 mph in Pennsylvania.