Relative humidity

2006-10-09 17:38:40.000 – Ryan Knapp,  Meteorologist

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The summit has, in effect, been a desert for the past three days. With strong subsidence beneath a massive ridge of high pressure the air was compressed and warmed. There was no feed of moisture from any direction as winds were nearly calm through a considerable portion of the lower atmosphere. The result was progressively lowering relative humidity values which bottomed out last night at 1.4%.

Let me say that again, 1.4%.

That is extreme.

What is even more impressive, between the 4 am and 5 am observations, subsidence ended which allowed the temperature to go from 48.5 degrees Fahrenheit with humidity of 4.2% down to 41.3 degrees Fahrenheit with humidity of 83%. When I was forecasting this morning, I did not expect us to moisten up as quickly as it did. I was expecting it to gradually rise through the day not shoot up in one hour. But this example illustrates how rapidly the weather can change on the summit and to remind visitors to always be prepared for rapidly changing conditions.

Ryan Knapp,  Meteorologist