(Issued: November 1, 2005)
Millersville University Weather Information Center (MUWIC)
Eric J. Horst, Director
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The last three months provided a classic study of weather extremes. The period of August 1st through September 30th was the warmest and second driest on record. A scant 2.10 inches of rain fell during August and September in aggregate. A sudden pattern change and infusion of tropical moisture then produced the wettest October on record with 9.04 inches of rain falling at the MU Weather Center.
The pivot point of the pattern change was on October 8th when over four inches of rain fell. In a mere twenty-four hours, the county shifted from being in a mini-drought to flood conditions. Two-day rainfall ranged from five to twelve inches with the heaviest rain occurring in eastern and southern parts of the county. The Conestoga Creek crested at the highest level in over 30 years, punctuating the dramatic turn of events.
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A strong, slow-moving cold front, coupled with remnant moisture from tropical storm Tammy, produced extreme rainfall across Eastern Pennsylvania on October 7th and 8th. Storm-total rainfall across Lancaster County exceeded the combined precipitation of the previous ten weeks. The village of Truce, in extreme southern Lancaster County, received a whopping 12 inches of rain.
Storm total rainfall reports:
http://snowball.millersville.edu/%7Ecws/storm_outlooks/coop_totalprecip_100805.gif
River stage and flow for Conestoga Creek (10/8-9/05):
http://snowball.millersville.edu/%7Ecws/storm_outlooks/conestoga_river_100805.gif
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Average High Temp: 64.9 F
Average Low Temp: 47.7 F
Average Monthly Temp: 56.3 F
(Departure from Normal: +2.4 F)
Precipitation: 9.04 inches
(Departure from Normal: +6.04)
Annual Precipitation: 31.84 inches
(Departure from Normal: -3.09)
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November features the largest beginning-to-end drop in normal temperatures. The month begins with pleasant average high/low temperatures of 60/38, but ends with much more winter-like normals of 46/28. Average rainfall for the month is 3.53 inches, while average snowfall is about one inch. Measurable snow occurs roughly once every four years. Extremes: Record high - 84 on 11/2/82; Record low - 1 on 11/29/38; Wettest November - 8.05" in 1972; Driest November - 0.58" in 1931 & 1938.
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In last month’s WIC Newsletter I made a confident forecast of an October pattern change that would break the multi-month trend of extreme warmth and dryness. As November begins, I have much less confidence in the evolution of the pattern in coming weeks. The month is beginning with a return of unseasonable warmth that will last through the 6th. I see, however, a strong signal of jet stream amplification over the eastern US around November 7th. If this verifies, the second week of the month will begin with seasonably chilly conditions and possibly some snow flurries in the mountains of Pennsylvania.
Still, I see no sign of us locking into a persistently cold pattern, nor do I see any indications that we’ll experience an “early start to winter” during November. Sure, most Novembers feature a measurable snowfall in the mountains of Pennsylvania and even some flurries in the Lancaster area. However, the idea that winter will commence early and strong – as put forth by numerous forecasting services – is not something the current pattern supports. It’s my sense that November will feature a wide range of conditions with periods of Indian Summer and a few spells of seasonable chill.
NOTE: Next month’s WIC Newsletter will feature my Winter Outlook!
COPYRIGHT 2005 Millersville University
Published monthly by the Millersville University Weather Information Center.
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