Flood — Montgomery, Pennsylvania
2011-08-28 to 2011-08-29 · near Pottstown, Montgomery, Pennsylvania
Event narrative
A 65-year-old woman on her way to work drowned in her car in the Wissahickon Creek in Fort Washington. In addition to the gaged creeks, the Unami Creek flooded in Marlborough Township.
The Schuylkill River at Norristown had major flooding and its fourth highest crest on record, highest since Hurricane Floyd in 1999. The river was above its 13 foot flood stage from 130 a.m. EDT on the 28th through 111 a.m. EDT on the 29th. It crested at 19.76 feet at 145 p.m. EDT on the 28th.
The West Branch of the Perkiomen Creek at Hillegass was above its 5 foot flood stage from 309 a.m. EDT through 110 p.m. EDT on the 28th. It crested at 5.58 feet at 830 a.m. EDT. The East Branch of the Perkiomen Creek at Schwenksville had major flooding, its fourth highest crest on record and greatest crest since Hurricane Floyd in September of 1999. The creek was above its 7 foot flood stage from 151 a.m. EDT through 429 p.m. EDT on the 28th. It crested at 12.91 feet at 1220 p.m. EDT.
The Main Stem of the Perkiomen Creek at East Greenville had record breaking moderate flooding. The creek was above its 5 foot flood stage from 128 a.m. EDT through 254 p.m. EDT on the 28th. It crested at 7.75 feet at 715 a.m. EDT. Farther downstream, The Perkiomen Creek at Graterford had major flooding and its second highest crest since July of 1935. The creek was above its 11 foot flood stage from 326 a.m. EDT through 637 p.m. EDT on the 28th. It crested at 18.20 feet at 1145 a.m. EDT.
The Wissahickon Creek at Fort Washington had major flooding and its third highest crest on record (since June of 2001). It was above its 9 foot flood stage from 1040 p.m. EDT on the 27th through 1249 p.m. EDT on the 28th. It crested at 16.22 feet at 345 a.m. EDT on the 28th.
Event rainfall totals included 7.08 inches in North Wales, 6.99 inches in Plymouth Meeting, 6.92 inches in Kulpsville, 6.88 inches in Willow Grove and 6.87 inches in Hatfield.
Wider weather episode
Irene produced heavy flooding rain, tropical storm force wind gusts with hundreds of thousands of outages, moderate tidal flooding along the Delaware River and one flooding related death in Eastern Pennsylvania over the weekend of August 27th and 28th. Moderate stream and river flooding occurred in the Poconos and Lehigh Valley and moderate to major river flooding occurred in southeast Pennsylvania. For many places in southeastern Pennsylvania, it was the worst creek and river flooding since Hurricane Floyd in 1999 or the remnants of Hurricane Jeanne in 2004. Flooding along non-tidal sections of the Delaware River was minor to moderate. There were two direct storm caused deaths: a wind related death in Monroe County and a drowning in Montgomery County. About 500,000 PECO Energy and 420,000 Pennsylvania Power and Light customers lost power in Eastern Pennsylvania. For both utilities this ranked within the top five outages of all time. Preliminary damage estimates were around six million dollars. In addition to property damage, the winds and rains badly damaged the corn crop in southeastern Pennsylvania. The Delaware Water Gap National Recreational Area was closed through Labor Day Weekend (September 5th).
Tropical storm force wind gusts overspread Eastern Pennsylvania during the evening of the 27th and persisted into the afternoon of the 28th. Peak wind gusts averaged around 50 mph. The strongest winds associated with Irene occurred at two distinct times. The first surge occurred during bands of heavier rain during the evening of the 27th and early morning of the 28th. The second peak occurred during the afternoon of the 28th when skies were clearing and deeper mixing of the atmosphere brought stronger winds to the ground. Most of the peak wind gusts occurred at this time. The rain associated with Irene overspread Eastern Pennsylvania during the late morning on the 27th, fell at its heaviest from during the evening of the 27th into the early morning of the 28th and ended during the early afternoon on the 28th. Event precipitation totals averaged 3 to 7 inches and caused widespread flooding. Because the flash flooding and flooding blended into one, all flooding related stormdata county entries were combined into one under flood events. The storm surge of 3 to 5 feet caused moderate tidal flooding along tidal sections of the Delaware River overnight on the 27th. Minor tidal flooding occurred during the high tide cycles from the 29th through the 31st.
In Stroudsburg (Monroe County), a 44-year-old man died when a tree fell on him in his backyard. He pushed his son to safety. Governor Tom Corbett declared a state of emergency for the city of Philadelphia and the surrounding suburbs. The Southeastern Pennsylvania Transportation Authority halted all commuter rail service during the evening of the 27th as multiple tornado warnings were issued. Three large shelters on the evening of August 27th in Philadelphia. The Philadelphia International Airport closed at 1030 p.m. EDT on the 27th and reopened on Monday the 29th. In Philadelphia, the storm left thousands without power. More than 500 trees fell in the city, seven buildings collapsed and twenty roads were closed. PECO Energy restored power by August 31st.
The highest wind gusts recorded during Irene were 57 mph in Mount Pocono (Monroe County), 53 mph in Allentown (Lehigh County), 52 mph at the Philadelphia International Airport (Philadelphia County), 48 mph in Reading (Berks County), 46 mph in Coatesville (Chester County), 45 mph in Northeast Philadelphia (Philadelphia County), 44 mph in Pottstown (Montgomery County), 44 mph in Newbold (Bucks County) and 40 mph in Quakertown (Bucks County). The high tide in Philadelphia reached 9.89 feet above mean lower low water during the early morning of the 28th. Moderate tidal flooding begins at 9.20 feet above mean lower low water.
Hurricane Irene formed east of the Leeward Islands on Saturday the 20th. It moved northeast and passed over Puerto Rico overnight on the 21st. As Irene moved off the island, it intensified into a hurricane. Irene just bypassed the island of Hispaniola to its north and then passed over the Eastern Bahamas on the 25th as it reached category three hurricane strength. From the Bahamas, Irene moved nearly due north and slowly weakened to a category two hurricane on the 26th and a category one hurricane on the 27th. Irene made her initial landfall near Cape Lookout, North Carolina at 8 a.m. EDT on the 27th and then proceeded to the northnortheast and went back over the Atlantic Ocean near the Virginia and North Carolina border at 7 p.m. EDT on the 27th. From there Irene paralleled the Delmarva Peninsula and the center passed about 15 miles east of Delaware between 3 a.m. and 4 a.m. EDT on the 28th. Irene made her second landfall as a tropical storm on Brigantine Island, just north of Atlantic City, New Jersey at 535 a.m. EDT on the 28th. From there the center of Irene moved along eastern parts of Ocean and Monmouth Counties and was located near Tinton Falls Township in Monmouth County at 8 a.m. EDT on the 28th. At about 9 a.m. EDT the center of Irene passed over New York City.
Irene helped shatter all time monthly precipitation records. In Philadelphia, the 19.31 inches of rain established a new all-time August as well as monthly record. It was nearly half of the normal yearly precipitation total. A new August as well as all-time monthly rainfall record of 13.47 inches was also established in Allentown.
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Source: NOAA Storm Events Database, event_id 343376. Narrative written by the NWS forecast office that issued the report.