August 09, 2001 11:00 pm

By Alice Perry Linker

Observer Staff Writer

Union and Cove were blanketed by smoke for a short time Wednesday, and the western end of the Grande Ronde Valley was hazy from field burning smoke Thursday afternoon.

A wind shift and change in the atmospheric pressure apparently caused the low smoke Wednesday afternoon, and a meteorologist said that by early Thursday morning, computer models were projecting poor ventilation and lighter winds poor burning conditions.

Burning was halted Thursday afternoon, said Steve Henderson, manager of the Union Countys Smoke Management Center. He acknowledged that the center received complaints both days.

The Department of Agriculture provides one morning weather forecast each day for the center, said meteorologist Irving Tillung.

By Thursday, the models indicated a more stable atmosphere, Tillung said. The smoke wont go up as high and will layer out.

This morning (Thursday), I found the mixing (of air currents) only half what it was yesterday and so I indicated a much lower mixing index, he said.

Lower mixing indicates that smoke will not rise in a plume but probably will spread across the valley.

A spokeswoman from the smoke management center at Imbler said a weather balloon launched Thursday morning indicated conditions were good.

Propane burning, not open field burning, caused smoke problems Thursday, Henderson said.

We put our propane to work with the wind, but the south wind didnt carry it out, he said. We had one small open burn in the north end Thursday.

Meteorologist Tillung said that the forecasting center does not receive information about the weather balloon results from the Imbler center.

We never know when theyre burning; we never see the piballs (weather balloons), and we dont know where they go, he said.

But Henderson said piball results are regularly faxed to the Department of Agriculture.

Weather forecasting is just another tool, he said. Theyre not perfect; we do use it a lot more (than in past years).

Tillung is predicting poor burning conditions for the next few days, as a high pressure system is causing hot afternoons and poor mixing heights, conditions that are not good for burning.

A committee appointed by the Union County commissioners spent several months during the winter and spring working on ways to improve forecasting and the measurement of air pollution. A new data ram measuring particles in the atmosphere has been installed at the Ag Services Center, but it has not yet been connected to the Imbler center. Henderson said the software for the program was received Thursday.

Commissioner John Howard, who organized the committee, said this morning that he does not know enough about the situation to comment, but he said, If it needs to be improved, well have to make the improvements.