Contact: Stephanie Kenitzer FOR IMMEDIATE RELEASE
Kimberly Comba 6/26/96
Oklahoma experienced its driest October-May period since record keeping began in 1895, and it may be at least a few more weeks before conditions improve for several drought-stricken states in the southern Plains and Southwest, according to a recently released Special Climate Summary by the National Weather Servicežs Climate Prediction Center in Camp Springs, Md.
The long-term drought is adversely affecting agriculture and creating prime wildfire conditions in the southern Plains and Southwest.
The special climate summary suggests that at least two short-term climate factors appear to be interacting, thereby contributing to the severity and longevity of this drought.
"One important climate factor that is contributing to the drought is the transition from an El Ni¤o warm episode to a La Ni¤a cold episode in the tropical Pacific Ocean during the past year," said Gerald Bell, Climate Prediction Center meteorologist and co-author of the summary. "Cold episodes often go hand in hand with a high pressure system over the Southwest, which diverts the jet stream and storm track northward, away from the drought-stricken region. The result is below normal rainfall across the Southwest."
The second climate factor is a persistent negative phase of the North Atlantic Oscillation, a naturally-occurring fluctuation of the atmosphere over the North Atlantic Ocean that influences temperature, precipitation, jet stream and storm track patterns from eastern North America to Europe. Over the past months, the oscillation has been "stuck" in a negative phase which features unusually high pressure at high latitudes of the North Atlantic Ocean and unusually low pressure over the central latitudes of the Ocean.
The combination of the La Ni¤a conditions and the negative phase of the oscillation during the past nine months are shaping the circulation patterns not only in the drought-ridden areas but across much of the Northern Hemisphere. Examples are a cold and stormy winter in the East, spring flooding in the Ohio Valley, and long-term cool and wet conditions reaching from the Pacific Northwest eastward to the mid-Atlantic states.
As of mid-June, the worst drought conditions were in New Mexico, Texas and southern and western Oklahoma, where less than 50 percent of normal total precipitation has fallen since October 1995, said Richard Tinker, a meteorologist at the Center and lead author of the special summary. The October-May period has been the second driest since 1895 for Texas, and the fifth driest for New Mexico.
The Center's 90-day forecast for July through September shows an equal chance for above-normal, normal and below-normal rainfall in the Southwest. However, the forecast shows that above-normal temperatures are most likely to occur in the region during the three-month period. Meteorologists at the Center use satellite data, atmospheric computer models and historical analyses to prepare these long-range forecasts.
"The most realistic chance for a significant break from the drought is during the late summer or early autumn monsoon which normally begins in July and ends in September or October," said Tinker.
The Special Climate Summary discusses the impacts and characteristics of the drought as well as outlooks and forecasts and is available on the Climate Prediction Center World Wide Web Home Page, http://nic.fb4.noaa.gov or the direct address is: http://nic.fb4.noaa.gov:80/products/special_summaries/96_2 Additional drought information is available through the National Drought Mitigation Center at enso.unl.edu/ndmc
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