MUWIC Newsletter - October 2006

(Issued: October 3, 2006)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: “Fall-like Weather Arrives Early”

Although Fall didn’t officially arrive until September 23^rd, an end-of-August pattern modification brought what felt like a change of seasons for the Labor Day weekend. A cool, damp start to the holiday weekend did give way to a sunny finish, however temperatures remained below normal throughout the weekend. This early chill was a harbinger of things to come—in fact, the month concluded as the coolest September in ten years!

Although the aggregate temperature anomaly for September was just one degree below normal, the average daily high temperature averaged nearly five degrees below normal. September normally features about ten 80-degree days and two 90-degree days—this year high temperatures reached 80 just three times and failed to reach the 90-degree benchmark.

Meanwhile, the topics continued to be uneventful for the United States as the four Atlantic basin storms named in September all remained offshore. View tracks of this year’s storms: http://www.wunderground.com/hurricane/images/at2006.gif

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EVENT OF THE MONTH

Severe thunderstorms crossed the county late on September 28^th. Rainfall topped two inches in a few locations, while hail and damaging wind gusts were reported in northeastern parts of the county.

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SEPTEMBER CLIMATOLOGY (MU Weather Station)

Average High Temp: 72.2 F

Average Low Temp: 56.0 F

Average Monthly Temp: 64.1 F

(Departure from Normal: -0.9 F)

Precipitation: 5.87 inches

(Departure from Normal: +2.25)

Annual Precipitation: 36.74 inches

(Departure from Normal: +4.81)

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OCTOBER NORMALS, RECORDS & FACTS

Normal rainfall for October is 3.00 inches making this the third driest month of the year.

The wettest October on record was in 2005 (9.04 inches); the driest was in 1963 when no

measurable precipitation fell. Normal high and low temperatures for October range from 71/47 (high/low) on the 1st to 61/38 on the 30th. The record high for the month is 95F (set on the 4th in 1941); the record low is 19F (set on several different days and years). Finally, Daylight Savings ends on the 29th.

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OCTOBER OUTLOOK

October is a month of seasonal transition and, thus, sussing out an overriding trend or bias is often difficult. This month is beginning with very active, fast flow as evident by the rare fall-time severe weather that’s occurred from the Midwest to the Mid-Atlantic region. Such flow will likely continue into mid-month with several strong cold frontal passages and resultant highly variable temperatures. The next few days will provide a nice case study of this pattern as a notable warm-up unfolds on October 3^rd and 4^th before a potent front ushers in unseasonable chill for October 5^th through 7^th. This pattern will likely recycle itself a couple of times through mid-October.

Beyond that it’s a very tough call, and I’m left with more questions than answers. Will there be a late-season burst of tropical activity? Will the jet stream lock into a pattern that brings us persistent chill or warmth? Or, will the current progressive flow and bipolar temperature tendencies continue through month’s end? My gut feeling is that late-October will bring an increasing bias for jet stream ridging in the western US while troughiness and increasing chill dominate in the Northeast. If I’m right, the higher elevations of northwestern PA may see their first snowflakes before Halloween.