Bill,
You got there what we call a Microburst. It is an interesting, and
isolated severe weather storm that is localized to a small spot, that
may not even at times show up on radar. We get them now and then in
Arizona. Nothing "unusual" - so to speak, other than that they are
very powerful. I watched one rip a building apart and leave the
buildings to either side untouched. Its almost like a tornado, but no
funnel clouds. You were lucky it didn't get freaky on you and toss
any vehicles around.

At 12:44 PM -0700 8/12/02, Bill N wrote:
>We were camping on Mt. Graham in SE Arizona this weekend when a very
>unusual event occured.  There were 9 of us sitting around the
>campfire around 4 in the afternoon on Saturday.  It was partly
>cloudy and calm.  Within a 30 second period it went from calm to
>winds I would estimate at 70+ MPH, and there was no warning.  We ran
>for our '81 Westy, and others ran for their vehicles.  We heard
>trees cracking all around us.
>
>Five minutes later, it was back to partly cloudy and calm.  There
>was no rain associated with this, and the whole thing lasted a very
>short time.  We hiked around taking stock and found that seven large
>ponderosa pines (2' or larger trunk) had blown down within 100' or
>our campfire, taking several smaller trees with them.
>
>Although the poptop was up, and the sliding door was open the whole
>time, the van had no problems.  The wind direction was from the
>rear, which I'm sure helped.
>
>Any weather experts out there have any idea what causes this sort of
>thing?  I am told by neighbors that a similar wall of wind blew
>through my home area (about 40 miles away) that same afternoon.
>
Bill in the Southwest
--

Happy motoring!

Timothy in Phoenix,
84 Vanagon (named Sparkii)
69 Bus (named Buster)