MUWIC Newsletter - October 2004

(Issued: October 1, 2004)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: "Frances, Ivan, and Jeanne Soak Commonwealth"

Three intense hurricanes made landfall on the US mainland in September and each brought some rain to the Commonwealth. First came Frances, which dropped up to six inches of rain across the western half of the state on September 8th. With a track well to our west, however, Frances brought only a few showers to the eastern third of the state. Ivan was the month's big event as his widespread heavy rain produced the most significant flooding of the Juniata and Susquehanna rivers in almost a decade. Then came Jeanne on September 28th, who fortunately produced only two to three inches of rain across the area, though, parts of the Delaware Valley received up to six inches of rain.

All totaled, September was one of the more rainy months on record across central Pennsylvania. Williamsport and Altoona recorded remarkable rainfall of 10.3 inches and 14.2 inches, respectively. Still, the impacts locally don't compare to that suffered along the Southeast and Gulf coasts. Damage estimates of 20 billion dollars make this one of the most costly hurricane seasons.

View tracks of this year's storms:

http://www.wunderground.com/hurricane/images/at2004.gif

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EVENT OF THE MONTH

The remnants of hurricane Ivan crossed the Commonwealth on September 17th and 18th dropping between one and nine inches of rain. The heaviest rain fell across the central counties with many locations receiving between five and eight inches. Rainfall amounts rapidly tapered off southeast of the mountains with some locations in southern Lancaster and Chester counties receiving only an inch of rain. Still, the widespread heavy rain across the Susquehanna River basin resulted in main stem flooding and the highest river stages since January 1996.

View plot of Ivan's rainfall:

http://www.erh.noaa.gov/ctp/features/Ivan/images/full_pa20040918.gif

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SEPTEMBER CLIMATOLOGY (MU Weather Station)

Average High Temp: 78.3 F

Average Low Temp: 58.7 F

Average Monthly Temp: 68.5 F

(Departure from Normal: + 3.5 F)

Precipitation: 4.38 inches

(Departure from Normal: +0.76)

Annual Precipitation: 34.22 inches

(Departure from Normal: +2.28)

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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 1932 (8.39 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 30th.

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OCTOBER OUTLOOK

October will begin with a couple above normal days, however, two strong cold fronts will move through in the days that follow. Seasonably chilly air will dominate across the Commonwealth from October 3rd to the 7th with the first widespread frost likely on the 6th or 7th. Following that, expect a spell of Indian Summer for the end of the week, as the pattern repeats itself into mid-month.

What I've outlined above is pretty much "normal" for October-that is, a progressive pattern featuring both tastes of Fall and brief flashbacks to late-Summer warmth. Such a pattern tends to be rather dry with only garden-variety showers as cold fronts move through. Large mid-latitude cyclones are rare in October, so any big rain events tend to be with the remnants of tropical systems.

Regarding the tropics, the worst is likely past for this season. Climatologically, three-quarters of named storms develop before the end of September. Still, I can't rule out a few more storms, and we'll have to keep watch on the Gulf of Mexico and Caribbean. As large chilly high pressure systems build south across the eastern US, strong easterly flow across the Gulf of Mexico can increase the chance of storm development. Thus, I will speculate that a tropical storm might form in the Gulf of Mexico or western Caribbean sometime between October 4th and 12th.