By Bill Robinson
Although his forecast of normal temperatures and rainfall for this past summer was way wide of the mark, state climatologist Dr. Stuart Foster is not afraid to offer a winter forecast.
Based on the best available data and scientific models, the National Weather Service expects Kentucky to have a winter that is cooler and drier than normal.
No one expected the cool, wet summer that Kentucky experienced this year, Foster said. The season included the coolest July on record.
The surprising weather was caused by the jet stream – a high-speed river of air in the upper atmosphere that has a strong influence – dipping much farther south than normal, he said.
Climatologists base long-range predictions on “mega factors” such as the jet stream, the high pressure cell that hovers over the North Atlantic in the summer and the temperature of the South Pacific Ocean, said Foster, who directs the Kentucky Climate Center at Western Kentucky University.
When the South Pacific’s temperature is slightly higher than normal, the phenomenon is called El Nino, Spanish for little boy. A slightly cooler ocean temperature is called La Nina, or little girl.
Even a slight variation in the distant southern ocean’s temperature can have far-reaching effects on weather in North America, Foster said.
His prediction of a cooler, drier this winter is based on the development of a moderate El Nino, he said.
Unfortunately for forecasters in the Ohio Valley, the El Nino and La Nina effects are felt more consistently in the north Central Plains and in the lower southeast.
The current El Nino should mean above average temperatures this winter in northern states such as North Dakota and Montana and below normal temperatures in Florida and the Gulf Coast.
The Ohio Valley, including Kentucky, is “betwixt and between” in another way that also makes weather prediction problematic. It is where the warm, moist air coming up from the Gulf of Mexico converges with cold air coming down from Canada.
In past interviews, Foster has called Kentucky a weather battleground.
Kentucky’s fall, as well as its winter and summer, also was unusual this year, said Dr. Greg Goodrich of the climate center.
October ranked among the wettest in the state’s history, he said. The month was followed by a November that ranked among the driest. Most of the state received less than one inch of precipitation in November.
Paducah received more than 10 inches of rain in October, a record. In November, a little more than half an inch of rain fell in the western Kentucky city, another record.
Jackson, where the National Weather Service maintains a radar station, also had its driest November on record.
For most of the state, November was three to four degrees warmer than normal.
Historically, it is very rare for a wet October to be followed by a dry November, Goodrich said.
Most private forecasting firms, such as nationally published almanacs, use El Nino averages, Goodrich said, but they also include things like the weather patterns over the previous summer and the strength of the previous hurricane seasons in their outlooks.
Since summer 2009 was below average in temperatures with above average precipitation, the private firms believe that this pattern will continue through winter and lead to above average snowfall, he said.
The Farmer’s Almanac is predicting a “very cold and snowy” winter for the southern Ohio Valley.
Most meteorologists discount the almanacs’ predictions, Goodrich said, because they tend to predict more extreme weather,
“As far as ice storms are concerned, there really is no way to predict the frequency of heavy ice,” he said. “But, an El Nino pattern can lead to the type of conditions associated with ice storms. However, the likelihood of having another historic ice storm this winter is rare.”
Bill Robinson can be reached at firstname.lastname@example.org or 624-6622.