Fog, Fog, Fog

2010-02-21 21:43:34.000 – Mike Carmon,  Staff Meteorologist

The week’s highlight vista

Due to the fact that fog is pretty much the lot of what we’ve experienced so far this shift week (5 days and counting…), I’ve had a pretty foggy mind, and would like to clear it by sharing some foggy bits with you.

There are many references to the phenomenon of fog in popular culture. In fact, part of my inspiration for this comment came from one of these references. A stand up comedian by the name of Eddie Izzard, in describing San Francisco during one of his stand-up routines, talks about its fog-a fog which sounds suspiciously like the fog we experience. I’ll quote him here, but just reading the words does not give the routine ANY semblance of justice.

‘ ‘I can’t see! I can’t see! Fog! There’s fog!’ I saw John Carpenter’s film The Fog…and I thought, well, that’s Hollywood…fog moving that fast…But your fog is that speed…It could be late…to…get in someone’s face somewhere…It runs down the road.’

That transitions nicely into my next pop culture reference-John Carpenter’s film The Fog, released in 1980. The film is set in the town of Antonio Bay, CA. The town, on the eve of its centennial celebration, experiences a number of supernatural events characterized by an ominous fog. The film stars Janet Leigh and Jamie Lee Curtis. The movie was recently remade in 2005, with a fairly identical storyline, and recast with contemporary actors such as Tom Welling (most famous for his role as the young Clark Kent on Smallville) and Maggie Grace (most famous for her role as Shannon Rutherford on Lost). Neither film was a blockbuster, but nonetheless, both are great pop culture affirmations of the menacing connotation so often associated with fog.

A much more realistic and morbid example of ‘killer’ fog was all too genuine for the residents of London in 1952. During an early-December week, a mix of dense fog and black coal smoke (smog) killed approximately 4,000 of its citizens, which is one of the deadliest environmental episodes in recent memory. A strong temperature inversion combined with relatively windless conditions trapped airborne pollutants over London. The soot and tar particles that make up coal smoke reacted with sulfur dioxide in the air to form a solute sulfuric acid. The deadly smog filled the streets and intruded homes, contributing to lethal conditions such as pneumonia, bronchitis, tuberculosis, and heart failure. Those with pre-existing conditions, such as asthma, died of respiratory distress, while others succumbed to cardiac distress and asphyxiation. Although this event is currently buried in obscurity, at the time, it was a colossal wake up call to the British and the world to take action in improving and preserving air quality.

On a lighter note, a poem by Carl Sandburg illustrates his observations of the fog phenomenon:

The fog comes
on little cat feet.

It sits looking
over harbor and city
on silent haunches
and then moves on.

As you can see, fog is all around us (especially on the summit of Mt. Washington) and will most likely always carry a mystical and somewhat sinister reputation with it.

So let’s turn around now and speak of fog from a more scientific standpoint. What exactly is fog? Its simplest definition is a cloud on the ground. When the air becomes saturated with water vapor, vapor will begin to condense into liquid water droplets. This is how clouds form. So, when the air is saturated at the surface of the earth, a cloud forms on the ground, and we call it fog. Think about it in this manner: if you’re in a plane, and you fly directly into the heart of a billowing cloud, how does the inside of the cloud appear? Does it not suspiciously remind you of fog?

Fog has a technical definition, according to the Federal Meteorological Handbook, No. 1, prescribed by NOAA. Fog (FG) is defined as ‘a visible aggregate of minute water particles (droplets) which are based at the Earth’s surface and reduces horizontal visibility to less than 5/8 statute mile and, unlike drizzle, it does not fall to the ground.’ If visibility is greater than or equal to 5/8 statute mile, but less than 7 statute miles, weather observers will report the phenomenon as mist (BR). Observers can further describe fog with other adjectives, such as shallow (MI), partial (PR), patches (BC), and freezing (FZ).

One of the many phenomena the observers up here on the summit can report in a weather observation is valley fog (VLY FG). This is a great demonstration of the atmospheric processes that result in a thick fog. During the night, air on the slopes of mountains cools, becomes denser than its surroundings, and descends into the valleys below. A pool of cooler air eventually forms in the valley, and if the dew point is reached, will form a thin layer of fog. Very often, on clear nights and mornings, our weather observations will contain the remark ‘PTCHY VLY FG’, meaning patches of valley fog are visible from the summit.

I am hopeful that I will be able to do an observation in the clear before I leave on Wednesday, but as of right now, my hopes for that occurrence are hastily dwindling. This is my fifth night working during this shift week, and I have yet to take out the sling psychrometer to perform a non-fog observation. As of 9:30 P.M. Sunday evening, my shift has performed 107 observations, and we have been immersed in the fog for 104 of them. I think that justifies my fantastically foggy comments here.


Mike Carmon,  Staff Meteorologist

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