Unsurpassed Clarity

2006-11-22 08:28:45.000 – Neil Lareau,  Meteorologist

Monroe Monday Sunrise

Yesterday. Yesterday was a good day.

By mid morning the persistent undercast that had allowed for nearly half a week of breath taking conditions had evaporated; its only trace was a collar of bright rime between 3500ft and 5500ft around the mountain. Looking at the photo (taken by Jon), you can see the history of the undercast marked in white. Flowing through the saddles from the west and descending into the Great Gulf. Rarely building into the Gulf from the east and banking against the interior slopes. The trace of cloud flow is as clear as high tide lines on a beach.

By noon relative humidity had dropped to 6%. Skies overhead were uninterrupted blue, and winds slackened.

By evening the air was clearer than I have ever seen; ever. The three of us – Jon, Mike, and I – all stood on the observation deck in awe of the resolution that the world had taken on. I’ve seen many incredibly clear days here; I’ve seen Mount Marcy 131 miles away many a time and yet never as clearly as yesterday. Standing in the weather room I could casually glance out the west windows and decipher with the naked eye the pyramidal form protruding from behind the Green Mountains. The clarity was in large part due to extremely low humidity and to a strong temperature inversion below the height of the summit. Inversions in effect provide an ultimately stable atmosphere (warm on top and cold down low) which prevents the mixing of pollutants and even moisture to the mountain top level of the atmosphere. Such a scenario also produces interesting optical effects as we look down into a layer of air with very different properties. In effect this is like looking at your feet while wading, diffraction (or bending) of the light occurs at the interface of the two layers. Extended over long distances, say 131 miles, this can amount to an effect called looming. Objects that would normally be hidden from view, like Mount Marcy, loom up above the horizon taking on a greater visual height than strict geometry would allow. Thus Mount Marcy was visible were typically I would see nothing…incredible. Oh and to top it off, inversions like yesterday’s are also very good at producing a ‘green flash’ when the sun sets. Last night didn’t disappoint. Mike Renzi enjoyed it.

This morning the good visibility is still with us, clouds from a coastal storm off the Carolinas are moving in overhead, and all of the region’s ski areas have fresh dollops of man-made snow contrasting an otherwise drab November landscape.

Neil Lareau,  Meteorologist