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Dear Tom, In the todays Tribune weather page (March...

March 11, 1998|By Tom Skilling, chief meteorologist at WGN-TV.

Dear Tom,

In the todays Tribune weather page (March 9) it says that the Meigs Field temperature is 37 (degrees) and the dewpoint 46 (degrees). This makes the relative humidity 141%. Is that possible? Or is it a measurement mistake? I thought that the humidity could never be higher than 100%. Thanks a lot.

Fr. John Pearson, Notre Dame, Ind.

Dear Father John,

Indeed the relative humidity cannot be higher than 100% since relative humidity measures the water holding capacity of the air. Reports of dewpoints higher than the temperature have been reported by weather equipment for years. These errors were usually caught by the human weather observer at the sight and corrected.

In recent years, these human weather observers have been replaced by completely automated systems, and it becomes necessary for a sharp-eyed forecaster at a distant sight to catch the discrepancy. In this case, the error was missed by the Tribune weather staff as well.



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