Isaias spawns possible tornadoes, torrential rainfall in mid-Atlantic

Tropical Storm Isaias was spreading torrential rainfall, strong winds and the threat for tornadoes across the mid-Atlantic on Tuesday morning - and forecasters say more flooding rain and tornadoes are possible along the Interstate 95 corridor of the Northeast throughout the day on Tuesday.

Several tornado reports have already been filed Tuesday morning across the Delmarva region. Multiple witnesses spotted a tornado in Queenstown, Maryland, which is located across the Chesapeake Bay from Baltimore, the Storm Prediction Center (SPC) reported. A vehicle was reportedly overturned.

Tornado reports and social media photos emerged from Kent and New Castle counties in Delaware Tuesday morning. Power poles were reportedly snapped just west of Dover, with several large tree branches down over roadways in the area. Emergency Management confirmed possible tornado damage to homes in Townsend and along Route 13 in Smyrna.

Just a few minutes later, a possible tornado touched down in Cape May County, New Jersey, about 2 miles west of Strathmere, crossing Route 50.

Earlier in the morning, Suffolk, Virginia, located in the southeastern part of the state, west of Norfolk, suffered a direct strike from a possible tornado, which left behind heavy damage, including numerous downed trees and power lines, and widespread roof damage to homes in the downtown area.

Two injuries were reported along with significant structural damage as a possible tornado tracked through eastern portions of Lancaster County, Virginia, early in the morning, according to the SPC.

Isaias, packing winds of 70 mph, was racing across eastern Maryland at a breakneck pace of 35 mph to the north-northeast as of 11 a.m. EDT Tuesday morning. The storm was located 70 miles southwest of Philadelphia.

Up to 7 inches of rain has fallen thus far in part of the mid-Atlantic from the storm. A gust to 94 mph was reported at a National Oceanic and Atmospheric Administration (NOAA) cooperative observer station at York River East, Virginia, and an 85-mph gust was observed at a station at Rappahannock Shoal, Virginia.

Isaias strengthened into a dangerous and damaging Category 1 hurricane prior to making landfall near Ocean Isle Beach, North Carolina, Monday night, and will continue to send copious amounts of moisture northward. The storm will pack enough wind to cause problems hundreds of miles farther north from when the storm was at its peak.

"Along and just northwest of the I-95 corridor of the mid-Atlantic and southern New England, heavy windblown rain with embedded severe thunderstorms will be the central theme from Isaias," AccuWeather Northeast weather expert Elliot Abrams warned prior to the storm hitting on Monday.

Strong winds from the storm cut power to hundreds of thousands of customers across eastern North Carolina and southeastern Virginia as the storm moved inland. A tornado is suspected of killing one person and injuring 20 others at a mobile home park in Windsor, Bertie County, North Carolina, during Monday night.

More tornadoes are expected to touch down through the day near and east of the track of the center of Isaias. The risk of tornadoes and waterspouts includes Virginia, Maryland, Delaware, eastern Pennsylvania, New Jersey, southeastern New York state and southwestern New England.

A tornado watch was in effect for central and southern New England during the late-afternoon hours on Tuesday, August 4, 2020. (AccuWeather/NOAA)

The National Weather Service issued a tornado watch from the Delmarva Peninsula to the New York City area and southern portions of Connecticut on Tuesday morning -- and the SPC posted an enhanced risk of severe weather along the same corridor. During late Tuesday afternoon the tornado watch was in effect from from southern New England to central New England as Isaias raced northeastward.

This water vapor image, captured on Tuesday afternoon, August 4, 2020, shows Tropical Storm Isaias centered over southeastern New York state. Dry air shows up as shades of orange and red.. Moist areas show up as shades of white, gray and blue. (NOAA/GOES-East)

All told, Isaias is predicted to cause between $2 billion and $3 billion in damage and economic loss, according to AccuWeather founder and CEO Dr. Joel N. Myers.

The center of Isaias may pass rather close to New York City, which would be the second storm of the season to do so following Tropical Storm Fay in early July.

"The last time there have been two named tropical systems pass so close in the same season was in 1985 when Gloria and Henri passed over Long Island, New York," AccuWeather Meteorologist Brandon Buckingham said.

"In 1960, Brenda and Donna passed within 40 miles of New York City," Buckingham added.

The track of Isaias will be somewhat different and will have different impacts when compared to Fay from early July. Isaias will initially track farther west and well inland over the mid-Atlantic compared to Fay, which moved onshore just north of Atlantic City, New Jersey.

Isaias's stronger winds have already affected more land areas of the coastal mid-Atlantic as well as a large part of the Chesapeake and Delaware bays compared to Fay. The storm surge caused by Isaias could be a few feet higher than Fay's, and coastal flooding could be significant. Gusts from the east and south may be stronger and could more easily knock down trees and cause more power outages this time from eastern North Carolina to eastern New York state and in portions of New England.

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Forecasters warn that people should not focus on just the center of the storm and the eye track. However, impacts from the storm will increase in area, and drenching rain will spread farther west as the system moves through the mid-latitudes. The strongest winds can extend well to the east of the center, particularly along the immediate coast.

Isaias has been deemed a 1 on the AccuWeather RealImpact™ Scale for Hurricanes in the U.S. The more nuanced scale introduced by the company in 2019 includes more factors than the winds of a tropical system and takes into account rainfall amounts and flooding impacts.

One of the main threats for the areas from Pennsylvania to Maine will be from torrential rain that can lead to flash, urban and small-stream flooding.

"An increase in forward speed is expected through Wednesday and the swath of heaviest rain will shift from east of the center to the northern and western part of the storm as it travels through the Northeast states," AccuWeather Senior Meteorologist Rob Miller explained.

A general 2-4 inches of rain is forecast from the accelerating storm in a narrow zone of the Northeast with locally higher amounts into Tuesday night. The heaviest rain has already fallen over parts of Virginia, Maryland and southern Pennsylvania from earlier on Tuesday.

In areas where the ground is rather wet, flash flooding can occur with a mere 2-3 inches of rain from the storm.

As of Tuesday mid-afternoon, Isaias has produced close to 7 inches of rain in Leonardtown, Maryland, and in Stafford, Virginia, with 4.06 inches at Goldsboro, North Carolina. More than 4 inches of rain has fallen from Philadelphia to Pottstown, Pennsylvania, with 5.20 inches falling on Quakertown, Pennsylvania, and 4.92 inches falling on Allentown, Pennsylvania.

This 24-hour storm total rainfall snapshot shows where the heaviest rain has fallen thus far as of 12 noon EDT Tuesday, August 4, 2020. Yellow areas indicate where it is estimated by radar that more than 3 inches of rain has fallen, while red areas indicate rainfall of 6 inches or more. Actual rainfall may be less than shown. (AccuWeather)

The zone from northeastern Pennsylvania and eastern upstate New York to northwestern New England will be at the greatest risk for flooding, based on the future track of this storm. The rain from Isaias has ended from New York City on southwest as of the mid-afternoon Tuesday.

In terms of wind, the strongest gusts will occur east of the track of Isaias and can reach strong tropical storm force along the immediate coasts of New England and southeastern New York state into early Tuesday night.

Frequent wind gusts of 40-60 mph are expected from southeastern New York state to New England.

Around New York City, during the early afternoon hours, a gust to 70 mph was reported at New York's John F. Kennedy Airport with a gust to 69 mph at LaGuardia Airport.

Runoff may still contribute to ongoing street flooding in this zone for several hours after the rain has stopped. However, due to downed trees and power lines, travel may be difficult, especially through side streets and secondary roads in the suburbs.

The gusts will become strong enough to knock over trees and break large tree limbs. "As the limbs come down, more power outages can occur over New England, and some streets and secondary roads may be blocked by debris as the storm moves along into Tuesday night," Miller explained.

Impacts from Isaias are likely to be more significant in some areas when compared to Fay from earlier this summer but perhaps not as bad as from Irene during late August 2011. Irene peaked as a Category 3 hurricane, while Fay was only a moderate tropical storm and Isaias is forecast to be at tropical storm strength while moving through the Northeast.

Coastal areas of New England will be at risk for a period of above-normal tides and storm surge flooding as the flow of air around Isaias directs ocean water westward for a time.

The greatest risk of a storm surge of 1-3 feet in the mid-Atlantic for the duration of the storm will be on the back bays from Delmarva to New Jersey as west winds push water eastward on the storm's back side into Tuesday evening.

Since the storm will be increasing its forward speed, the period of strong winds and coastal flooding may be limited to 6-12 hours in eastern New York state and New England.

Following its impact on the U.S., Isaias is forecast to spread a swath of rain and gusty winds rapidly through a portion of Atlantic Canada from late Tuesday night to Wednesday.

The 2020 Atlantic hurricane season has already left its mark in history with several of the earliest-forming tropical storms on record. Cristobal, Edouard, Fay, Gonzalo, Hanna and Isaias all set early-season formation records for their respective letter. All of the July-forming storms from Edouard through Isaias broke the records set during the infamous 2005 season.

Hanna became the first hurricane of the 2020 season, and Isaias became the second.

There is a high potential that the 2020 season could become "hyperactive" as the peak of hurricane season nears and tropical storm numbers may end up rivaling the historic 2005 season numbers, which produced 28 storms. AccuWeather meteorologists are already monitoring a few areas of disturbed weather beyond Isaias.

It's not just meteorologists who need to keep a close eye on how storms develop and where they're heading. AccuWeather users can now do that from home using our local hurricane tracker pages that provide detailed information about a specific location.

Click on the city name to track how Isaias will impact each place as it churns northward: Ocean City, New Jersey; New York City; and Boston, Massachusetts.

Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.