Hopewell Furnace National Historic Site And Valley Forge National Historical Park: Weather Of 2008

Knight, Paul; Wisniewski, Tiffany; Bahrmann, Chad; Miller, Sonya

The purpose of this report is to provide a concise climate summary for 2008 at Hopewell Furnace NHS and Valley Forge NHP, as part of the Mid-Atlantic Network's Weather and Climate Monitoring Program. Specifically it contains summaries for weather, temperature, and precipitation and descriptions of observing stations, stream flow, and draught status. The winter months were unseasonably mild, averaging nearly 1.9°F (1.1°C) above normal, while the spring months (April–June) were also warmer than average; due, in part, to the 19th warmest April on record which had more than a third of the days reach maximum temperatures of 70°F (21.1°C) or higher. The summer was slightly cooler than average, while autumn was the only three-month period of the year that was unseasonably cool, compared to the long-term means. Overall, 2008 was warmer than normal (though a tenth of a degree cooler than the previous year), ranking as the 31st warmest year on record (57 is average). Though drier than in recent years, 2008 was considerably wetter than normal. The wettest period of the year was the second week in September, during which 5.1 in (130 mm) of rain fell in a 7-day period. This was aided by rains from Tropical Storm Hanna on September 7, which dropped over 3 in (76 mm) in a 24-hour period. The driest periods of the year were the first two-thirds of October, as well as the middle of August. The dryness of the late summer and early autumn was reflected in the flow patterns of Valley Creek and French Creek. The snowiest month was January, when 4 in (10 cm) of snow fell, including 3 in (6 cm) on the January 18, the highest single-day total of the year. Additionally, a severe weather outbreak on June 10 resulted in reports of hail as large as 1 inch (25 mm) in diameter and numerous downed trees and power lines. The highest temperature recorded during the year was 98°F (36.7°C) on June 10, while the lowest temperature was 11°F (-11.6°C) on February 11. There were 12–19 days on which the temperature reached at least 90°F (32°C), which is lower than the 30-year mean (Table 1). However, there were only 9–12 days when the maximum temperature failed to reach 32°F (0°C), six to nine less than the expected value. There were 10–14 days when precipitation totals met or exceeded an inch (25 mm), which is close to the 30-year average. However, a mild winter resulted in only 12–15 in (30–38 cm) of snowfall, below the 30- year mean of 19 in (49 cm). Despite the lack of snowfall, moist conditions were prevalent during the winter and autumn seasons, which is shown by the Palmer Drought Severity Index for PA Climate Division 3, which encompasses most of Hopewell Furnace NHS and Valley Forge NHP. The trend of increasing solar radiation continued in the long-term despite being in a solar minimum since 2007.

Hopewell Furnace National Historic Site And Valley Forge National Historical Park: Weather Of 2008

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