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Interesting day at the top of Mt. Washington

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  • steve_03222
    17:38 PM Mon Oct 9th 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
    Message 1 of 1 , Oct 10, 2006
      17:38 PM Mon Oct 9th

      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
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