MUWIC Newsletter - September 2005

(Issued: September 6, 2005)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: “Third Warmest August on Record”

Hazy, hot, and humid. Add “dry” to the list, and you have a good summary of August’s weather conditions here in the Susquehanna Valley. The Bermuda high pressure system that developed in mid-July remained the controlling factor throughout most of August. This stable airmass suppressed the development of afternoon showers, despite plentiful low-level moisture in the form of unusually high dew points. Barely an inch of total rainfall was measured at the MU Weather Information Center, growing the year-to-date rainfall deficit to over five inches.

Temperature-wise, August 2005 was the third warmest on record with a temperature anomaly of +4.6 degrees. While high temperatures reached the 90-degree mark on nine days, the unusually high overnight lows (averaging 6.5 degrees above normal) were most remarkable. This trend of above normal overnight lows and unusually high humidity has been a hallmark of this summer across our region.

Departure from Normal (DFN) of High & Low Temperature Summer 2005

High DFN Low DFN Overall (comment)

June +1.7 +5.3 +3.5 5^th warmest

July +0.5 +4.2 +2.4 11^th warmest

August +2.7 +6.5 +4.6 3^rd warmest

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EVENT OF THE MONTH

This month’s event—Hurricane Katrina—will go down as the “event of the year” and “event of the new century.” Category 5 storms are extremely rare, and this vicious storm unfortunately made landfall (as a Category 4) on a large city that’s mostly below sea level. While the story is still unfolding, it seems apparent that Katrina will gain the infamous distinction as the most costly natural disaster in American history.

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AUGUST CLIMATOLOGY (MU Weather Station)

Average High Temp: 86.8 F

Average Low Temp: 68.3F

Average Monthly Temp: 77.6 F

(Departure from Normal: +4.6 F)

Precipitation: 1.08 inches

(Departure from Normal: -2.89)

Annual Precipitation: 22.82 inches

(Departure from Normal: -5.49)

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SEPTEMBER NORMALS, RECORDS & FACTS

Fall officially arrives at 6:23 p.m. on the 22nd (autumnal equinox). Normal rainfall for September is 3.62 inches, and normal high and low temperatures range from 82/59 (high/low) on the 1st to 71/47 on the 30th. On average, there are eight days with measurable precipitation (third lowest monthly average) and two days with a high temperature of 90F or above. The record high for September is 99F (9/3/53) and the record low is 27F (9/26/22).

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SEPTEMBER OUTLOOK

The mild and dry conditions we experienced over Labor Day Weekend will continue for the next seven to ten days as I see very little change in the overall pattern anytime soon. High pressure will maintain the trend of mostly sunny and pleasant days; this combined with dry ground conditions and westerly wind flow means that daytime highs are likely to remain a couple degrees above normal. Fortunately, the source region of low-level air is increasingly from southern Canada, making for lower, more comfortable dew points and overnight night temperatures.

Given the above pattern, there will be little chance of significant rainfall outside the possible input of tropical moisture from the deep south. The active hurricane season looks to continue this month with several systems developing in the Atlantic and, possibly, one or two storms threatening the Gulf or East coasts. One such storm will meander near Florida and the southeast coast through September 10^th—beyond that, it’s uncertain if the system will turn northward towards our region or track into the Gulf (and potentially threaten the central Gulf coast).

Outlook Summary:

Ø Temperatures will average 1.5 to 3.0 degrees above normal

Ø Precipitation will average below normal (<3.62”) barring a tropical event.

Ø Another tropical storm or hurricane is likely to make landfall somewhere along the Gulf or East coasts.