NOAA REPORTS JULY COOLER, WETTER
THAN AVERAGE IN THE EAST,
August 14, 2003 ó In much of the East, rainfall was unusually heavy and average monthly temperatures were generally cooler than average. Record and near-record heat affected a large part of the western United States in July, and below-average precipitation contributed to persistent or worsening drought conditions throughout much of the region, according to scientists at the NOAA Climatic Data Center in Asheville, N.C.
NOAA scientists report the average temperature for the contiguous United States in July (based on preliminary data) was 75.7 degrees F (24.3 degrees C), which was 1.4 degrees F (0.8 degrees C) above the 1895-2003 mean. It was the twelfth-warmest July since national records began in 1895.
Numerous daily and monthly all-time records were established across the West, as a dominant high pressure area persisted throughout the month. The monthly mean temperature in every western state—except California—was much warmer than average, and Idaho had its warmest July on record. In Phoenix, Las Vegas, Cheyenne, Wyo., and Grand Junction, Colo., July 2003 was the warmest month on record.
The Western warmth contrasted sharply with cooler-than-average temperatures in much of the East. Twelve states from Mississippi to Pennsylvania were significantly cooler than average. Upper-level winds in the atmosphere pushed unusually far south in the eastern United States in July, leading to generally cooler and wetter-than-average conditions. This continued a pattern that has persisted for much of the spring and summer.
Seventeen states east of the Mississippi were significantly wetter than average in July, and May-July was the wettest late spring-mid summer period in four states (Alabama, Tennessee, Virginia and Ohio). The same three-month period was the second wettest on record in four other states (Georgia, South Carolina, West Virginia and Indiana).
While wetter-than-average conditions covered much of the East, the same ridge of high pressure that brought record heat to the West also resulted in below average precipitation in many states. Fourteen states west of the Mississippi were significantly drier than average for July. Four of those states (Kansas, Colorado, Wyoming and Montana) were much drier than average, and New Mexico had its driest July on record.
The heat and lack of precipitation occurred in many of the same states that have experienced drought for the past three to five years. At the end of July, 70 percent of the West was in moderate to extreme drought, based on a widely used measure of drought, the Palmer Drought Index. This was an increase of 11 percent since June and 21 percent since the end of May, continuing the reversal of a short-term trend toward improving conditions that had begun late last year. The most widespread drought on record occurred in July 1934 when moderate to extreme drought affected 97 percent of the West. The persistence of unusually warm and dry conditions over the last several years has created conditions that rival those experienced during the drought years of the 1930s and 1950s in parts of the West.
Land surface temperatures for July were the third warmest in the historical record. Much warmer than average temperatures were widespread across Europe, which was affected by a severe heat wave during the month. Daily high temperatures routinely exceeded 90 degrees F (32 degrees C), and at times 100 degrees F (38 degrees C), across many areas from France and Switzerland southeastward across the Mediterranean region.
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