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July 31, 1979 STORM-TRACK Vol. 2, No. 5

3415 Slade Court $2.10/year Bi-monthly
Fairfax, Virginia

I. COMMENTARY [by David Hoadley]
In case you missed it, the June 18 issue of Time carried a 3 page article on the pre-eminent
tornado chaser, Gene Moore. It is written around Gene’s participation in the NSSL chase program
and conveys some of the chase experiences familiar to all of us. Although it tends to exaggerate
the dramatic, the mood and tempo of the chase are realistically conveyed, and the writer suceeds
in putting everyone in the back seat with Gene. As already noted, this article relates Gene’s
experiences in support of NSSL. It does not, publicize chasing -as such- as a hobby but, as a
scientific aid to storm research. Thus, I was relieved to find no particular encouragement to the
lay public to take this up as a casual past time. It is indeed rare when something that, one is
totally dedicated to is also that in which one excels and achieves national recognition, as well.
Here’s wishing all the best to Gene. I trust that his well deserved reputation will now lead to
even better things for him.

Here is an address change for a previous Roster entry:
Name Address Chase country-range
John M. Brown 3960 Darley Avenue
Boulder, Colorado 80303

Dr. Walter A. Lyons, Certified Consulting Meteorologist and President of MESONET, INC. is looking
for cloud and storm slides to develop and expand his new “Weather Graphics Service” for television
weathercasters and educators. MESOMET is a multifaceted meteorological and environmental firm, and
its Weather Graphics Service provides slide packets at a subscription fee, including all types of
clouds, from fog and stratus to high clouds and all the severe clouds between. MESOMET’s
collection of over 20,000 slides “will be improved and updated” periodically, and slide packets
will be upgraded accordingly to provide variety -over time.

Dr. Lyon’s credentials are impressive and include the AMS Seal for Television Weathercasting and
appearances on the ABC network as well as various technological advancements, including the first
color radar echo animation system.

Dr, Lyons has developed a comprehensive Slides Usage Agreement that clearly spells out his
obligation to the slide contributor. I will not elaborate on the terms of the Agreement, but the
contributor is promised 20% of receipts attributable to slide usage. For additional information,
write to Dr. Walter A. Lyons, President, MESONET, INC., 190 North State Street, Chicago, Illinois

FUNNEL FUNNIES: A Stop for Road Directions

— contributed by David Hoadley


VI. FEATURE – Severe Windstorms in Colorado [by John M. Brown”>
When I moved to Boulder from Ames, Iowa, about a year ago, I figured that chances of experiencing
any severs weather of consequence nearby were minimal. I had heard of Boulder’s reputation for
strong winds, but an intense Iowa thunderstorm is hard to beat. My opinion on this latter point
hasn’t changed, but Boulder windstorms have proved to be both enigmatic and fearsome.

The most wind-prone areas average 5-10 days a year during which the peak gusts are at least 75
mph, and 1-2 times a year on which gusts to 100 mph or more occur. The peak gust reported in the
Boulder area during the past 10 years or so is 147 mph on top of a building at NCAR (National
Center for Atmospheric Research). January is the month with the highest frequency of very strong
winds, but high winds can occur any time of year (August 14, 1978 a peak gust to 88 mph was
reported and substantial tree damage).

These strong winds always blow from the west and are -thus- downslope. A schematic sketch of the
gross aspects of the flow during a typical event, depicted in cross section, is given in the
figure below. The dominant feature is the large-amplitude “mountain wave” shown by the streamlines
with arrows. This feature has been observed by research aircraft flying traverses across the
mountains. The inversion (or stable layer), indicated west of the Divide, is thought necessary to
induce the tremendous amplitude of the wave. Forecasting strong winds in Boulder, then, requires
an accurate forecast of conditions over and upstream from the Continental Divide. The west winds
east of the Divide rarely extend far out into the plains. Boulder, being adjacent to the
foothills, receives more strong winds of this type than any other city in Colorado (or the USA).
Denver, 30 miles SE, is almost never affected (although suburbs west of Denver are).

Figure showing schematic airflow in a west east cross section across the Boulder area, The curved
lines with arrows are streamlines; the spacing between these is approximately inversely
proportional to wind speed. Typical locations of clouds are shown. The cloud over the plains just
east, of Boulder is lenticular in form. The cap cloud along the Divide usually obscures the
mountain peaks.

The strongest winds I have experienced so far came the afternoon of December 4, 1978. At NCAR,
which sits atop a 6,000′ mesa jutting eastward from the nearby “foothills” of 8,500′ and overlooks
Boulder 500-800′ below, two gusts to ll5 mph were reported. In Boulder itself, rapid melt of a
heavy snowfall 3 days earlier led to intermittent blowing of spray and sand (from earlier street
sanding), making for difficult driving. I also heard, for the first time in my life, a continuous
“freight-train roar” such as is sometimes described by tornado survivors.

In the parking lot, at. NCAR late that afternoon, I spent several minutes observing the following.
The wind was less than 20 mph about 60% of the time! However, there was a low background noise of
wind roaring through pine trees. Soon, this would become concentrated to the west and grow louder.
Suddenly, a dominating screech would emanate from the NCAR buildings (150 yards west), lasting
only a few tenths of a second, as the gust hit wires on the roof. Then the roar grew louder as I
prepared for the onslaught by turning around to face east, squinting and bracing myself. Thus
prepared, I succeeded with difficulty in remaining on my feet. The onslaught lasted only a few
seconds and was over, the roar passing to the east,. This pattern repeated 4-5 times in the 5-10
minutes that I stood in the parking lot, observing it.

Surprisingly, only minor damage was reported in Boulder, mostly broken windows. IS such a storm
were to strike Ames, particularly in summer, damage would have been much more severs. My hometown,
San Diego, would be completely paralyzed by such a storm. In Boulder, many storms of similar or
greater intensity have occurred over the past 10 years, leading to strict building codes and
widespread public awareness of wind related hazards.

Next issue will feature my own experience with a tornado like roar.

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