September 27, 1998 Severe Thunderstorms

As mentioned above, the thunderstorms were ahead of a cold front. An unusually warm and humid airmass was in place over PA and surrounding areas. Record high temperatures which had stood since the turn of the century were broken in several areas. Both Harrisburg and Philadelphia reached 91 degrees! Remember this is very late September. Other records were shattered at Allentown, PA, and Binghamton, NY, airports (where official readings are taken). The Wilkes-Barre/Scranton International Airport missed their record high by 1 degree. Dew points were in the 60's across Pennsylvania... showing just how humid it was for the northeastern U.S. while approaching October. There was several hours of sunshine during the morning and early afternoon, leading to destabilization of the atmosphere. CAPE's were up to 1,000 in PA, and LI's dropped to -5. Although neither number is impressive, especially the CAPE, they were enough to support severe thunderstorms. I think that the reason a solid squall line did not form is because of the non-impressive instability factors. Probably one of the biggest things that got the severe thunderstorms going was the soupy airmass (high dew points), and heating from the sun. Just a short time after sunset in the early evening, the thunderstorms decreased in intensity as they lost their power source.

Thunderstorms developed first in southern New York State during the early and mid afternoon hours, and it took until 3:00 pm for storms to form in most of PA. A few of the thunderstorms in NY were severe, downing trees and power lines. One of the severe thunderstorms in westren NY dropped very large hail... actually some of the largest ever recorded in that part of NY. The largest stones (which were more than 3 inches in diameter - larger than baseballs!) were not able to be photographed. Still, pictures were taken of some of the large hailstones. Two of the severe thunderstorms in south central NY moved into northeast PA, namely northern Bradford and northern Susquehanna counties. Numerous trees and lines were blown down in Sayre, Athens, and Little Meadows. Large hail also fell in a couple spots, with radar reflectivities over 60. SPC issued a severe thunderstorm watch for most of PA around 3:30 pm, excluding the extreme eastern counties (also see redefining statement from CTP). The first severe thunderstorm warning in PA was issued for Clarion county in western Pennsylvania, at 3:52 pm. Severe thunderstorm warnings continued to be issued for other counties around western and central PA through early evening. One thunderstorm in Mercer county downed trees and power lines in the town of Mercer, and in Grove City... where dime size hail also occurred. One tree landed on a house and another on a porch. Large limbs were ripped out of trees in Dayton, Armstrong county, with dime size hail falling in Dayton and Templeton. Elk City in Clarion county had some damage from the severe thunderstorms, including trees down, a shed destroyed, and windows blown out of a house. Trees and lines were blown down in the town of Warren, with trees down in west central McKean county and DuBois as well. Potter county had trees and power lines blown down countywide. Hail as large as dimes fell in northwestern Butler county, namely Harrisville. Dime size hail also fell in Altoona, with trees down from the thunderstorm winds. A spotter in Plumville, Indiana county, reported winds to 60 mph from one thunderstorm cell. Zion in Centre county had tree limbs blown down, along with a few power lines.

The first real notable damage occurred in far northern Cambria county, in west central PA. Thunderstorm downburst winds cut a 7 mile long, 1 mile wide swath of tree damage... starting just east of Hastings and ending east of Patton around St Augustine. A gustnado spun up within this downburst, as damage patterns in some areas indicate. Damage was somewhat scattered until just southeast of Patton, to St Augustine. Here, winds reached peak speeds of around 70-80 mph, causing extensive tree damage (more than a hundred were blown down). A 2100 gallon water tank was moved a 1/4 mile! One house roof was damaged from a falling tree outside of Patton. Just east of St Augustine, part of a barn roof was lifted off the rafters and set back down. Crops were flattened near the barn, with rotation shown in the field. A large pen filled with Game Pheasants sustained damage when plastic netting was ripped off and blown to the north of the pen. Some pheasants flew away, while a couple dozen were killed. Dime size hail fell in Hastings. Roads were also blocked from trees and power lines.

Near the Clinton/Lycoming county border, areas around Avis and Jersey Shore were also hit by severe thunderstorms. Trees were down, power poles were snapped, and a roof was torn away from a house by the damaging thunderstorm winds. A tree damaged a house as well. Radar showed the severe storm at the approximate time of the damage. As the thunderstorm moved southeast into northeastern Union county, it became very intense and showed some rotation. A hook echo was even shown for a time. A tornado warning was issued at 6:16 pm for Union county. The thunderstorm continued to grow in intensity, and radar at 6:26 pm showed a rare 70 dbz over northeast Union county! For a brief time, radar even showed a very small area of 73 dbz! Sizeable hail was falling at this time, and a powerful burst of thunderstorm winds was in the process of being produced in White Deer township. The downburst/microburst moved parallel and just south of Interstate 80, for 7 or 8 miles. It started several miles west northwest of New Columbia and continued east southeast into New Columbia. Along the edge of this microburst, the NWS says an F0/F1 gustnado was produced, which had a 2 1/2 mile path length and a 1/4 mile width. Between both the thunderstorm and tornadic winds, hundreds (perhaps over a thousand) of trees were blown down!! Almost all of the damage was from the downburst thunderstorm winds. I'm not sure I agree with the NWS confirmation of a gustando, which you will read in my storm survey linked below. Although houses are hard to come by in that particular area, one was damaged by falling trees. Damaging winds destroyed several sheds, and ripped off parts of roofs from three barns. A metal silo also collapsed. Peak winds were estimated to be around 85 mph. A swath of large hail also fell, causing damage/destruction to thousands of acres of crops. Two days after the damage occurred, on the 29th, I completed a storm survey of the area. It took a good 3 hours, and my report is here, with numerous damage pictures included.

The severe thunderstorm continued into northern Northumberland county, producing another downburst and gustnado... roughly 3 miles east of Milton... in Turbot township. The tornado/gustnado was rated a low F1... with peak winds probably not over 80 mph. Again, like the damage in Union county, most of the damage was from downburst winds. Parts of roofs were ripped off of two barns. The large metal section of one landed in the owner's driveway. Numerous trees were downed by the localized storm, with one limb being thrown with such force that it went through the wall of a house! Dime to quarter size hail also fell with this severe thunderstorm. At 6:36 pm radar showed the severe thunderstorm in the vicinity of Milton. It was about now when the damage was occurring. Worth of note, I live just a few miles north (outside of Watsontown) of the damage area and I recorded thunderstorm winds to just 24 mph, and had mostly moderate rain (was heavy for 40 seconds). At that time, it was hard to imagine the violence that was ocurring so close...

The severe thunderstorm continued to move east southeast into Montour county. Although the base reflectivity data showed a decrease in intensity 10 minutes later, at 6:46 pm , remember that the reflectivity data does NOT show wind, but rather the intensity of precipitation, such as rain and hail. At this point, wind was the primary threat. The thunderstorm produced its last damage, before weakening below severe limits, in downtown Danville (southern Montour county). Winds ripped through the city streets, sending debris flying. Part of the roof of a business was ripped off and landed on the steps of the building next door.. the post office. It tore down a light before hitting the pavement. A couple blocks away, a garage roof was blown off and landed on a pick up truck, which received damage. Trees were also blown down in the town. One landed on a van, belonging to a church. The van was crushed/totaled. On the outskirts of Danville, a barn roof was torn away. A severe thunderstorm warning was issued for northern Northumberland and Montour counties before the storms hit. It appears that quite a large number of local residents were watching TV as the warnings went out, and were able to hear them. They took the proper actions to protect themselves, as they told the media. Note: unlike the damage in Northumberland and Union counties, where a tornado/gustnado was partially involved, the damage in Danville was all due to thunderstorm winds.

This was the last damage reported due to the thunderstorms on this date. The notable aspect of these thunderstorms were this: They were scattered, never a solid line, but there was several areas of considerable damage. The thunderstorm that started in Clinton county produced several distinct areas of damage in 5 counties. LSR's and PNS's are archived for the event.

A complete listing of all images/text available for this event can be found here. Included are numerous radar images not linked above.