11.   Despite chilly surface temperatures, a few solitary thunderstorms will erupt in the resulting general, broken pattern of rain across the southern Plains.

12.   El Nino occurs in tropical regions of the Pacific Ocean when trade winds slow, allowing surface temperatures in the Western Hemisphere to heat up.

13.   El Nino conditions, characterized by warm sea surface temperatures in the Pacific, impact weather conditions throughout the world.

14.   Gray said he has been reducing his forecast because Atlantic Ocean surface temperatures have been cooler than expected in April and May.

15.   He said rainfall levels in West Africa are more likely to be influenced by changes in sea surface temperatures in tropical regions of the Atlantic than by El Nino.

16.   He said that the cause of the cold spell was elusive, but probably is related to complicated shifts in patterns of ocean surface temperatures.

17.   In addition, he peered at the frothing waters below and at his radar screen to estimate wind speed, sea surface temperature and other characteristics of the storm.

18.   In addition to direct warming of the surface, he proposed that hot plumes might alter deep currents to affect surface temperatures.

19.   In Ohio and West Virginia where surface temperatures are several degrees warmer, snow will mix with or change to rain.

20.   Meanwhile, pockets of ice will fall further inland where surface temperatures hover near freezing.