August 16, 1997 Derecho Event

A fairly unusual moderate risk was issued by the SPC for generally the northern half of central and eastern PA, northern NJ, and southeast NY. The first severe thunderstorm warnings came out for northwest PA between midnight and 1 AM in the morning. Severe thunderstorm watches were in effect before hand. By 11 AM, the SPC put the northern half of PA under a severe thunderstorm watch, expecting the derecho to continue producing wind damage (see all watches, in order of issuance, here ). Throughout the afternoon, severe thunderstorm warnings were issued for all of PA's northern counties, including my county (Northumberland). During the evening hours, the derecho finally weakened, as it moved across New Jersey and Long Island, NY, but deaths and injuries were still reported. However, the severe weather was not over for PA just yet. Rather unexpected, new severe storms quickly developed during the evening hours over northwest PA... behind the derecho system. These storms were just as serious, and spun out an F2 tornado in Erie county!

Definately worth of note, was that the airmass over PA/OH was extremely, and unusually, unstable. LI's were as low as -10 in some areas, and CAPE values were as high as 5,000!

As mentioned before, this derecho started to our west northwest in the early morning hours. It was just as strong then, and caused quite a bit of damage in Michigan. Here is a brief summary of the damage there:

In Lenawee & Monroe counties, Severe thunderstorms produced $55,000 worth of damage, almost all of it due to damage at a campground outside of Cement City. Just south of Temperance, several trees were uprooted... injuring a mother and her 4 year-old daughter in a tent. The 4 year-old suffered from a skull fracture, and was rushed to the hospital where she was listed in critical condition. Other damage occurred in southern and lower MI, but no other injuries were reported.

The derecho then tracked across mainly the northern half of Ohio, killing two people in Lake Erie outside of Cleveland, when they were knocked overborad by a combination of strong thunderstorm winds and wind-driven waves (a 62 mph gust was recorded). Four other boats were capsized, and 12 additional people were thrown into the water, but luckily rescue workers were able to reach these people before fatal injuries occurred. Elsewhere across northern and eastern Ohio, many trees were downed, some falling on houses and cars, causing tens of thousands of dollars in damage total. More severe thunderstorms developed behind the derecho from mid afternoon on. An F1 tornado touched down very briefly, but still ripped the roof off a middle school in Medina county. Some more minor damage (window, siding) ocurred to the school, and numerous trees were also down. More than $300,000 damage was reported! A few other tornadoes occurred, these rated F0, in Richland, Lorain, & Medina counties. The only one that did damage was in Medina township, Medina county (separate from the F1). Numerous trees were downed, and survey teams found that a downburst may have contributed to the damage. By far, thunderstorm winds/downbursts did most of the damage in northern and eastern Ohio. Many, many trees were down, some very large (3 feet in diameter!). Numerous roads were blocked, & trees fell into houses, garages, mobile homes, and cars, causing about $250,000 in damage. In addition, lightning struck a few buildings, and the following fire caused considerable damage. In Summit county, one hundred acres of corn was blown down, as well as numerous trees. Also in Summit county, several trailers were damaged by thunderstorm winds, resulting is $20,000 damage. Flash flooding was reported in a few places too, and cars were submerged, with several thousand dollars in damage.

The following paragraphs will give a fairly detailed summary of the damage across Pennsylvania, New Jersey, & Long Island, New York:

First, we'll take a look at some enhanced satellite images, showing the MCS crossing northern PA and NJ. By 1:15 pm, it had entered north central PA, and by 3:15 pm, it was approching northeastern PA. A couple hours later, it was over northern NJ and southern NY. Also take note of the large area of thunderstorms over northern OH and northwest PA. These are what caused a lot of the damage in western PA, and the F2 tornado in northwest PA.

PA damage from derecho event and the severe storms that developed behind the derecho--

Note: If you are not familier with PA counties, use this map.

In Erie county, a large building was destroyed 5 miles west of downtown Erie by thunderstorm winds. The estimated cost of the building and its contents was roughly $50,000. Elsewhere in Erie county, trees were reported (there are always downed trees that go unreported) down in Edinboro. When severe storms developed behind the derecho, later in the day, a tornado was produced by one of the thunderstorms in Union City. For most of the time, it had F1 winds, but at one point it strengthened to an F2! In the twisters 2 mile path length and 100 yard width, it skipped along, damaging 20 mobile homes, and destroying one... in the Maple Heights Trailer Court. Also, it leveled a huge concrete block building... measuring 60x80 feet! Three houses and one business were damaged, a cornfield flattened, and a few trees were knocked down. Damage was up to half a million dollars ($500,000) in property, and $3,000 in lost crops. Amazingly, there were no injuries due to the tornado.

In Crawford county, about 100 trees were downed, along with many powerlines in the city of Meadville. In addition the county fair was left in shambles. Up to $50,000 damage was done, a good portion due to the serious damage to the county fair.

In Allegheny county, a lightning strike started a house fire in Bakerstown Station that severely damaged the second floor. $20,000 in damage was done. Also, hail of 1" in diameter fell in Sewickley Heights, and large tree branches up to 2 feet in diameter were blown down by thunderstorm winds.

In Lawrence, Beaver, & Butler counties, thunderstorm winds downed a tree onto a house in Enon Valley, causing minor damage. Trees and/or power lines were also downed 6 miles northeast of Butler, in Butler, Cooperstown, Ellwood City, Koppel, Slippery Rock, Wick, Eau Claire, Bessemer, New Wilmington, New Castle, Industry, Economy, Baden, & Ambridge. Several roads were blocked. A tree fell onto a car in New Galilee, and a mobile home was moved along with its skirting ripped off the base. Quarter size hail was reported at the same location, while dime size hail was reported in Hillsville. Lightning struck a shed and burned it to the ground in Hazen.

In Mercer county, thunderstorm winds down trees & powerlines in Grove City, 5 miles west of Greenville, and in Greenville a couple different times. Dime size hail fell in Mercer, and substantial street flooding occurred in Sharon & Grove City. Also 2 miles west of Sharon, thunderstorm winds caused major damage to the roof of a house.

In Venango, Clarion, and Jefferson counties, thunderstorm winds downed trees and/or power lines in Polk, Utica, Clintonville, West Freedom, Brookville, Reynoldsville, and Brockway. 2 miles north of Cherrytree, lightning struck an open stage, injuring a male security officer.

In Armstrong and Indiana counties, thunderstorms winds downed 10-15 trees in Parker City, one falling across a house, and another falling across two vehicles... causing several thousand dollars in damage. In Smicksburg, at least one tree and several large branches were brought down onto route 954. Trees were also down in Apollo and Gilpin township.

In Washington county, in the town of Washington, trees were downed and a shed was destroyed by thunderstorm winds. In West Middletown and vicinity, a large maple tree fell and crushed a camper, with numerous other trees down blocking roads. Trees were also down, some blocking roads, 3 miles south southeast of Washington, and 1 mile north of Greensburg.

In Westmoreland county, scattered trees were down throughout the county, with the most from Herminie to Ligonier. A lightning strike sparked a barn fire in Donegal.

In Fayette & Greene counties, a large tree was down 1 mile northwest of Bobtown, blocking route 2023 in Greene county. In addition, numerous trees and power lines were downed from Republic to Farmington in Fayette county.

In Warren, Mckean, and Elk counties, trees and/or powerlines were down in Warren, Youngsville, Spring Creek, Russell City, and Johnsonburg. A tree fell on an outbuilding in Mount Jewett, and on a trailer in Bradford. Some other large trees were down in the Kinzua Bridge State Park. A roof was blown off of a house in Pittsfield. Quarter size hail (1") fell in Kane.

In Cameron, Potter, and Tioga counties, trees were down in Tioga and Wellsboro as well as several other areas in the county, with many trees down in Galeton. Trees and a traffic light were blown down in Emporium.

In Clearfield and Blair counties, trees were down in Clearfield, Curwensville, Kylertown, and Irvona... where a couple fell on a farmhouse.

In Centre and Clinton counties, trees were down in Philipsburg, Bellefonte, Lamar, Westport, and Lock Haven... where powerlines were also down. A tree was also down on a road in State College. A telephone pole was down in Rote.

In Lycoming county, a swath of tree damage occurred, and a shed was blown down in the Cedar Run area. The Williamsport/Lycoming county airport recorded a 58 mph thunderstorm gust, with trees down in Montoursville, the location of the airport. Many trees and powerlines were downed in Williamsport, some blocking roads. A few of the trees were quite large, crushing cars and damaging houses to varying degrees. In Muncy, a peak gust to 60 mph was recorded by a SKYWARN spotter, with trees down. In Montgomery, a tree fell on a house near the Susquehanna boat club, with minor (relatively) damage. Trees and lines were downed in other areas of the county as well, and one man was killed in Pine township when he came into contact with a downed live power line.

In Union, Snyder, and Mifflin counties, trees and/or powerlines were down in New Columbia, and eastern parts of Snyder county... including Selinsgrove. Many trees were down throughout eastern Snyder county, and road construction signs and barriers were blown along the highway, damaging a few cars, with at least one car window knocked out. A showroom window in a car dealership was also shattered by strong thunderstorm winds. In parts of Mifflin county, including Milroy, some trees and lines were downed.

In Sullivan county, there was one death and one injury. This county was probably the hardest hit. An expansive area of downburst winds hit a large portion of Sullivan county. While most of the damage was downburst winds, a couple areas showed rotation in the tree damage, and two tornadoes were confirmed by NWS survey teams. The downburst winds first started their tree damage in the Hillsgrove area, but the first area of rotation began near High Knob in the Wyoming State Forest. Damage was sporadic for much of the time, but at one point over a hundred trees were completely stripped of their branches, and just a straight, very narrow, tree trunk was left. Winds were probably between 65-75 mph, placing the tornado at the upper limits of an F0 & lower limits of an F1. A 45 year old woman was injured by a falling tree limb while hiking in the High Knob Natural Area. The indication of rotation continued about 5 miles just south of east (ESE) to just north of Eagles Mere Lake, in Eagles Mere Park. Rotation stopped in this immediate area. All damage was to trees, except a vehicle was demolished by a falling tree on the north side of Eagles Mere Lake. Another tornado was confirmed to have touched down north of the Eagles Mere Airport, crossing over route 42. It moved east and crossed Laporte Avenue in southern Eagles Mere borough. The path length of this tornado was 1-2 miles, and was rated an F1. Again, most of this damage was downburst in nature, but tornadic signs were noted. All together, hundreds of trees were downed in the Eagles Mere general area, mainly just north and just south of downtown Eagles Mere. Since most of the area is just trees, no structures were affected. This was the last area of good rotation, but the downburst winds cut a swath of damage (mainly to trees) many more miles long, across Sullivan county past Laporte and Lopez. Another area of thunderstorm downburst winds, with a very small area of embedded tornadic winds, struck southeastern Sullivan county. Hundreds more trees were downed and damaged in this area, including in Ricketts Glen State Park. This is where the fatality occurred to a 15 year-old boy. As trees were being knocked down all over, one fell on the tent he was in, resulting in fatal injury. It is a miracle that no one else was killed, as there were tens more people there. Several campers reported trees coming down within a few inches of them!
Luckily, all the trips on the motor launch, which carries passengers around Eagles Mere Lake, was suspended for the day because of the threat of severe weather. Other boats were allowed in the lake during the day, but when severe thunderstorm warnings were issued for Sullivan county, they were all called in. If they had ignored the severe thunderstorm warnings, as some of the public does, injuries and deaths could have been worse.

In Lancaster and Schuylkill counties, trees were downed in Adamstown, and hail as large as 1" (Quarter) broke numerous windows. Trees were downed across Schuylkill county, including in the city of Pottsville.

In Northumberland, Montour, and Columbia counties, trees were downed across all three counties. A 60 mph thunderstorm gust was measured in Mooresburg, wires were down in Catawissa, and trees & powerlines were down in Millville, Unityville, Benton, and just outside of Danville. Several miles west of Danville, a tree fell on a vehicle at routes 642 & 45, in Liberty township. A maple tree fell onto a house in Riverside, causing porch and roof damage. A tree branch fell on a car in Northumberland, smashing out the front and rear windows, while a tree fell on a house and opened a crack in a ceiling. Local residents described the falling trees as very loud "thuds"... jolting the whole neighborhood. Trees were down blocking roads in Milton, Watsontown, Turbotville, and Pottsgrove.

In Bucks, Chester, Lehigh, and Northampton counties, tree limbs were down in West Chester & Sadsburyville. In Doylestown and New Hope, wires were down, and a few telephone poles were snapped. From Germansville to Coopersburg, trees and wires were downed. In Bethlehem, thunderstorm winds as high as 63 mph lifted the roof off of a stage at the Musikfest celebration. Scores of trees were downed in Northampton county, especially in the northern half of it. More trees were reported down by severe thunderstorms in Bath, Fords, Bangor, Roseto, and Moore township. Numerous trees were downed in Easton, and one crushed a car. In Bath, a lightning strike started a fire that ran through a row of townhouses, leaving 6 families homeless and causing $100,000 in damage.

In Monroe county, parts of the area was hit hard by severe thunderstorm winds/downbursts, especially in Smithfield township and the Delaware Water Gap National Recreation area, along the Delaware river. Three people were injured in the recreational area, as trees and limbs fell on campers and cars. Winds in localized sections of Smithfield township were estimated to be as high as 85-90 mph at times. Wind gusts were measured up to 70 mph. The size of some of the trees that were uprooted is mind-boggling. Absolutely huge trees that have stood for 100+ years were snapped like toothpicks, and others were uprooted, letting the tremendous root span be seen. Many were uprooted in the Spring Lake Development. Four major roads were closed because of tens of trees down on them. One of them was closed for more than a day (26 hrs)! At least three homes were damaged. Windows were blown out of the East Stroudsburg High School, and wind damage occurred to the Hamilton School too.

Bradford, Susquehanna, and Wyoming counties, experienced widespread wind damage, mainly in the form of downed trees and power lines. In Bradford county, western and central sections had the most trees down, and in Susquehanna county, eastern sections (roughly east of Interstate 81) had the most tree damage. Numerous large trees were downed along route 92, and one landed on a pick-up truck. In Wyoming county, damage occurred across the county, from Mehoopany to Tunkhannock to Factoryville... again, mainly in the form of uprooted trees and power lines. However, some siding damage did occur to several buildings.

Northern and central Luzerne county, as well as Lackawanna county experienced wind damage. Large trees were uprooted in Harveys Lake, and more trees and utility poles were downed Glen Lyon and Jackson township. A mobile home was violently ripped off its foundation near Fleetville and split in two. A tree was then thrown into it. In the town of Wyoming (not Wyoming county), many trees, some large, were downed. A light pole and a couple utility poles were also snapped right in half. At Pocono Downs Raceway, in Plains township, large utility poles and transformers were brought down by the thunderstorm winds. A window was also blown in. They lost an estimated $40,000, since they had to close that night. In Pittston township, at least three homes lost their roof shingles. In the city of Wilkes-Barre, many roads were completely blocked by downed trees and powerlines. A few large advertisement signs, with steel braces, beside roadways in the city were blown down, one ripped apart. In Scranton, more trees and power lines were down, some on houses. In southern parts of Nanticoke, the steeple was blown off a church, falling to the ground and cracking in half. Trees and power lines were downed in the area too. Some large trees were downed, crushing a few cars. In South Abington township, a wedding reception was nearly destroyed. Winds blew trees down, threw tens of chairs across a field, as well as other objects. A SKYWARN spotter measured a 58 mph thunderstorm gust in Moosic township, and many trees and power lines were knocked down in East Benton and Baylor's Lake. Some of the trees were absolutely tremendoes. One residence suffered considerable damage from falling trees. One of them fell straight through the roof of part of his house, and came to lay on the floor inside. The second one destroyed half of their deck, while another sandwiched the families station wagon. Yet another one, probably the largest, missed his house and car, landing on the lawn when it was uprooted. This was a huge cherry tree, with a very large root span. A bulldozer was needed to remove it. Power lines were a tangled mess around the area. A few of the neighbors said they'd lived there for 40 years and never seen anything like this. The father of the damaged household rushed his family to the basement when he noticed the strong winds developing... likely saving their lives.

Pike and Wayne counties were also hit with damaging thunderstorm winds. We'll start in Wayne county, where a man was killed when the strong winds capsized the boat he was in, on Lake Wallenpaupack. A severe thunderstorm warning was issued for the area, but unfortunately he did not heed it. Numerous other residents in the area said that they had a NOAA weather radio and took shelter in a strong building when the severe thunderstorm warning was issued. Many large trees and power lines were downed from Lake Ariel to Hawley, as numerous downbursts slammed onto earth. In Pike county, a narrow swath of tree and power line damage moved across the northern portion of the county, roughly from Lackawaxen, southeast to Milford and Matamoras.

New Jersey damage from weakening derecho event--

In Warren and Sussex counties, trees and powerlines were down in Warren county, mainly along the Delaware river. However, trees and lines were down in a few other locations around the county. In Sussex county, a bit more damage occurred, from Colesville to Stanhope. However, most of the wind damage was in the northeast half of the county. A 64 year-old man was killed when a tree fell on him outside of his home in Green township. Franklin borough was especially hard hit, and a limited state of emergency was declared. 6 major roadways were closed within the borough. Several trees fell on houses and damaged them moderately. Siding was ripped off other houses, and on others, railings were ripped off of decks. A couple homes had the entire deck torn off of their house. Part of Hardin Lumber's roof was torn off. Lightning set two houses on fire in the town also. The borough of Sussex was hit hard as well, with a state of emergency declared. Again, 6 major roadways were closed, with other backroads also closed. A few of the roads were closed for more than a day. At the Sussex airport, a couple planes were flipped over, with pieces from them landing in the woods. Trees up to 150 feet tall were uprooted by the damaging thunderstorm winds! Other locations reporting wind damage are Sparta township, Fredon township, Hopatcong, Lafayette township, Vernon, and Wantage. Wind gusts throughout the damaged areas were in the 60-70 mph range.

In Hunterdon and Morris counties, more fairly widespread wind damage was reported. Scores of trees and powerlines were downed in Hunterdon county, with a tree falling on a person. This person suffered serious injuries and was brought to the hospital immediately. A SKYWARN spotter recorded a 60 mph thunderstorm wind gust in Flemington. The hardest hit areas include Flemington, Clinton, Glen Gardner, Quakertown, Raritan, and Ringoes. In Morris county, more widespread trees were downed, as well as power outages occurring. A 53 year-old man from Denville died from a heart attack, after being hospitalized for injuries caused from being hit by a four foot wide tree limb. There were so many downed wires on state route 10, that it looked like spaghetti. Trees fell and blocked parts of Interstate 287. The borough of Mountain Lakes had 36 reports of downed trees! In Montville township, a home had a 100 year-old tree come right through their roof. One house in Boonton township was so badly damaged by fallen trees, that officials feared it would have to be condemned. Other towns reporting trees down include Denville, Chatham, and Rockaway.

In Somerset, Middlesex, Monmouth counties, a few trees and lines were down in Somerset and Middlesex counties. In Monmouth county, a severe thunderstorm ripped down trees and limbs in Holmdel. A 34 year-old woman was killed when a tree fell on the car she was driving. In Asbury Park, lightning ignited a fire in the second floor of a two story building. $15,000 damage resulted.

In Passaic, Essex, Union, Hudson, and Bergen counties, numerous trees, some large, and power lines were downed. Some roadways were blocked. A tree fell onto a house in Maplewood, and a shed was blown away in Ringwood. Traffic lights were downed in Woodridge. Three people were injured in these counties, one in Newark, when a tree fell and pinned the person. A 58 mph peak wind gust was recorded at the Caldwell airport. Heavy rain flooded roads in central Passaic county, including in Totowa. When water got to deep, roads were forced to close.

Long Island & New York city damage from weakening derecho--

By now the derecho has weakened considerably, but still caused damage and death. First in Westchester county, the southern most county in NY state (excluding LI), three people were injured in Yorktown Heights from falling trees/limbs. In Manhattan, a roof blew off a building and was deposited on train tracks at the 125th street Broadway subway station. A 58 mph thunderstorm peak gust was measured at Central Park. In Bronx, thunderstorm winds downed a tree that crushed and killed a woman, and critically injured her two children. In Nassau county, thunderstorm winds overturned a boat in Oyster Bay. A man and woman fell overboard, and the man was injured and rescued. The woman, unfortunately, was accidently run over by a power boat and died soon after. A 58 mph thunderstorm gust was reported in North Massapequa, and numerous trees and powerlines were downed in Garden City, where a person was injured. The line of thunderstorms weakened even more over Suffolk county, not producing any reported damage.

Unfortunately, quite a few people died and were injured throughout this severe thunderstorm event, all but one resulting from damaging thunderstorm winds. Virtualy every derecho event that occurrs claims lives, some more than others. Most of these deaths and injuries could be prevented. How? HEED SEVERE THUNDERSTORM WARNINGS!! The National Weather Service issues these warnings to protect life and property, and only that. If a severe thunderstorm warning is in effect for your area, don't go out and get the mail, or take a walk in the park.... which is how two of these deaths and injuries occurred. If you're on a lake or near coastal waters and a warning is issued, GET TO SAFETY NOW. A few of the deaths were attributed to the neglect of seeking safety out of lakes/seas when a severe thunderstorm warning was issued. However, credit must be given to the people at Eagles Mere Lake, Sullivan county, who did listen to the severe thunderstorm warning. It is almost certain that more deaths and/or injuries would have occurred otherwise. Thunderstorm winds can overturn boats and create high waves fairly easily. Even a large vessel can be overturned by a strong downburst. It has happen before, with tragic consequences. The reason airplanes don't take off or land anymore near most thunderstorms is because of the microburst danger. Hundreds of people have died in plane crashes as a result of thunderstorm microburst winds.

With the normal severe thunderstorm, winds do not exceed 100 mph, but rather range from 55-65 or 70 mph. Thunderstorm winds of these speeds are capable of blowing down trees and power lines, overturning unanchored mobile homes, damaging some homes (with peak gusts), and pushing moving vehicles off the road. Although all thunderstorms don't produce downburst winds over 100 mph, some do. Thunderstorm wind gusts have been recorded at 158 mph once, near Washington DC. Normally, these type winds (80, 90, 100 mph+) are seen in bow echo or derecho events, but even small thunderstorms can occasionally produce these type wind speeds. When a severe thunderstorm warning is issued for your area, if you live in a very well built home, the "average" severe thunderstorm won't severely damage it. However, the "average" severe thunderstorm is capable of blowing in windows, which can result in serious injury. For your protection, move in an area without windows or glass doors. Also, do not seek shelter in sheds or other outbuildings, as they are also damaged or destroyed by the average severe thunderstorm. Mobile homes that are not tied down are very easily overturned by light severe thunderstorm winds. Tie them down or get out when a warning is issued! When thunderstorms are producing wind speeds of over the average severe storm (say, 75 or 80 mph+), all residents should take shelter in the lowest level of their home, of course away from glass. Thunderstorm wind speeds of this magnitude can damage virtually anything in its path. Remember, a thunderstorm wind gust is stronger than any other type of sustained wind of the same speed. This is the reason that a 75 mph sustained hurricane wind does little or no damage, but a 75 mph thunderstorm gust will cause enough damage.

A complete listing of all images/text available for this event can be found here.