After a cold front dropped our temperatures into the 40s Tuesday, warmer air will move back into the region as a broad ridge of high pressure builds up across the west coast. There will be occasional cloudiness for the rest of the work week, but temperatures will climb into the upper 50s Wednesday, and then peak out in the low to mid-60s through the rest of the week. Come Sunday, we are in for a near repeat of last with another storm system coming in that will kick up some winds and bring another round of snow to the mountains with a chance of valley showers.

barometer

Yesterday, I told Marci to set her son’s barometer to the same inches of mercury reading the airport reports. But she said “It’s marked in ‘hPa,’ not inches. Does that make a difference?”

hPa chart

Indeed it does. hPa stands for hectopascal, or 100 Pascals. A Pascal is the standard metric unit of pressure. One atmosphere of pressure (the approximate pressure you will find at sea level) equals just over 100,000 Pascals. So a hectopascal is roughly equal to one thousandth of an atmosphere, and is exactly equal to one millibar.

It actually makes more sense to use hPa for pressure when it comes to the international community, but we Yanks just have to be different, and we’ve adopted inches of mercury as our public standard.

 

 

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