MUWIC Newsletter - June 2007

(Issued: June 2, 2007)

 

Millersville University Weather Information Center (MUWIC)

Eric J. Horst, Director

 

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LEAD STORY: May Turns Warm and Dry

 

After a cooler- and wetter-than-normal April, a reversal in the weather pattern yielded the tenth-driest May on record. The month began with a beautiful nine-day stretch with mainly clear skies, near-normal temperatures, and not a drop of rain. Following the damp April, this extended period of sunny days made for a dramatic start to the local growing season.

 

The second half of the month turned definitively warmer as high temperatures reached into the 80s on eight days. A summerlike pattern—complete with a Bermuda high pressure system—then set in for the Memorial Day weekend. The result was July-like heat and humidity that eventually led to some late-weekend showers and thunderstorms. Still, the month’s total rainfall (MU Weather Center) only tallied 1.24 inches (just one-third of normal rainfall for May). Surprisingly, current stream flows and ground water levels remain at or above normal, despite drying soil conditions.

 

You may be wondering if the recent dryness is a precursor to a summer drought. Perhaps. A review of similarly warm and dry Mays (what we call “analogs”) reveals a strong signal for a warmer- and drier-than-normal June to follow. Fortunately, the weather pattern in the coming days looks to turn increasingly unsettled with a good chance of widespread and frequent shower activity. Should we receive an inch or more of rain in the next week, this would greatly improve surface dryness and lower the threat of developing drought conditions.

 

2007 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)

 

TOTAL: 14.67 (-1.28)

 

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EVENT OF THE MONTH

 

Sunday, May 27th brought a few heavy storms across the Lancaster area. Hail was reported many areas, and gusty winds resulted in several power outages. Total rainfall, however, was modest with less than a half in falling in most locations.

 

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MAY CLIMATOLOGY (MU Weather Station)

 

Average High Temp: 76.5 F

Average Low Temp: 52.0 F                                                   

Average Monthly Temp: 64.3 F                                         

(Departure from Normal: +2.4 F)

                  

Precipitation: 1.24 inches  

(Departure from Normal: -2.38)   

Annual Precipitation: 14.67 inches              

(Departure from Normal: -1.28)

 

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JUNE NORMALS, RECORDS & FACTS

 

Normal high/low temperatures range from 80/54 on June 1st to 85/61 by month’s end. The record high for June is 103 degrees set on the 20th of 1923 and 29th of 1934. The lowest temperature recorded in June is 33 F set on the 5th of 1921 and the 8th of 1932. Normal liquid precipitation for the month is 3.88 inches. The rainiest June on record (14.14 inches) occurred in 1972 when the remains of Hurricane Agnes moved through the region. The driest June was in 1966 when only 0.54 inches fell. Summer officially begins on June 21st at 2:06 p.m.

 

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JUNE OUTLOOK

 

As stated above, analog forecasting techniques signal a high likelihood for a continuation of the warm and dry trend into June. Only three out of ten May analogs were followed by a wet, cool June. Thus, it can happen; but the analog signal supports a normal to warmer-than-normal month ahead.

 

The wild card in the June Outlook is the outcome of this weekend’s weather. An uncommon confluence of two systems—a potent jet stream trough from the Plains and a very moist system from the southeast—could produce heavy rainfall across the Mid-Atlantic region. Should we receive one to three inches of rain over the first week of June, that would not only alleviate the current surface dryness, but it also would help moderate the daily high temperatures by a few degrees.

Nationwide, I expect the mean trough position to remain in the West with ridging from the Plains eastward (in the mean). This would lead to above-normal temperatures across the nation’s midsection—and this heat will frequently expand eastward to the Mid-Atlantic and into the Southeastern states. Temperatures will likely exceed 100 degrees in the southern Plains, as well as in some of the parched areas in the Southeast (and perhaps Mid-Atlantic). The bottom line: I fear a hot, dry summer across much of the nation’s heartland and portions of the East—in fact, above-normal warmth could continue right into the Fall season.

 

COPYRIGHT 2007 Millersville University

 

Published monthly by the Millersville University Weather Information Center.

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