MUWIC Newsletter - July 2007

(Issued: July 18, 2007)

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

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LEAD STORY: “Mellow Start to Summer”

A spring-like weather pattern dominated throughout the month of June as persistent northwest flow brought frequent cold fronts and scattered showers. While temperatures surged into on the 90s on five days, there was a notable absence of sustained heat. In fact, the average high temperature for the month was nearly one degree below normal.

Meanwhile, a jet stream ridge remained over the western half of the country leading to widespread extreme heat from the Rockies to the West coast. Drought and fire danger continued across much of the west, while the East continued in a moderate pattern with frequent showers. Locally, year-to-date rainfall is within the normal range.

Lancaster Rainfall by Month (departure form normal)

January – 2.33 (-0.68)

February - 2.40 (-0.07)

March – 3.66 (+0.28)

April – 5.04 (+1.57)

May – 1.24 (-2.38)

June – 3.77 (-0.11)

TOTAL: 18.44 (-1.39)

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STAT OF THE MONTH

After the tenth driest May on record, measurable rain fell on 15 days in June. Total rainfall for the month varied widely (depending on thunderstorm tracks) with between 3 and 6 inches recorded by various gauges around the county.

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JUNE CLIMATOLOGY (MU Weather Center)

Average High Temp: 81.7 F

Average Low Temp: 62.5 F

Average Monthly Temp: 72.1 F

(Departure from Normal: +1.8 F)

Precipitation: 3.77 inches

(Departure from Normal: -0.11)

Annual Precipitation: 18.44 inches

(Departure from Normal: -1.39)

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JULY NORMALS, RECORDS & FACTS

Climatologically the warmest month of the year, daily average temperatures peak on July

18th and 19th with a normal high/low of 88/63. The record high for July is 104 degrees set on three different occasions (July 3, 1966, July 10, 1936, and July 21, 1930) and the

record low is 42 set on Independence Day in 1918. Normal precipitation for the month is

4.51 inches. The rainiest July on record occurred in 1941 when 9.48 inches fell. The

driest July was in 1955 when only 0.60 inches fell.

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LATE-SUMMER OUTLOOK (Issued: July 19, 2007)

At the mid-point of meteorological summer (June, July, and August), lack of extreme heat is the most remarkable aspect. High temperatures have reached the 90-degree benchmark only ten times—that’s five times few than what is normal at this point of the summer. Furthermore, the warmest day (July 10^th) featured a high of just 93 degrees; by comparison most summers produce at least a couple highs in the mid to upper 90s by mid-July.

Looking ahead, however, I do see a changing weather pattern. The recurrent trough and parade of cold fronts into the eastern states looks to be fading. An upper-level low will linger over the Northeast through July 25^th, and therefore prevent any 90-degree days in the next week. However, the Plains ridge will expand eastward by the last few days of July and I do believe that a Bermuda high may take hold into early August. As a result, I do expect several more 90-degree days in the coming weeks and there will likely be an extended period of hazy, lazy Dog Days conditions in August. However, I do not see temperatures ever reaching the century mark this summer, nor do I think we’ll reach the normal number of 90-degree days (25) for the summer season.