Garmin 396 Weather avoidance..

Dan wrote:
For those of you with a Garmin 396, how do you avoid dangerous weather,
avoid yellow and steer clear of the lightning strike indications? I am
considering the purchase of one and am wondering how to use the info
safely, but yet with the maximum utility.

Dan,

I have only been in a few such situations since I bought the 396 last
year, and my experience is that you can fly through green all day long.
Yellow is okay as well provided it's not convective (forecasts, a
nearby lightning strike or cell data icon are a few ways one may
determine that). I always stay clear of red, since it's always
convective. The deep orange color can go either way -- I remember a day
of soaking rains that were displayed as yellow and orange, but there
were no thunderstorms in the area because the temperature and
atmospheric conditions simply didn't support convection on that scale.

I have also confirmed the lag in delivery and concur with the other
poster who suggested you determine the direction of movement and
circumnavigate on the upwind side of the cells only. I was flying
commercially one day, relocating an aircraft for some jump operations,
and had to wind my way through many cells.

I expedited my departure from the Danbury, CT airport as I watched one
cell about 10NM in diameter approach the airport. The outer edges of
the cell, depicted as green, reached the edge of the airport where I was
doing my runup when light rain started. But that cell was crawling --
almost stationary.

Enroute, I watched one cell literally explode and move at better than
30K. It took a mere three updates (15min) from this to go from one
pixel, or 2sq nm green (a "harmless shower") to a cell being tracked
upwards of 25K feet with lots of red in its core. As I watched it in
real time outside the window, it was clearly several (7-10) miles ahead
of its indicated location, though the diameter of the rain shaft
appeared roughly correct.

I just flew from NJ to SC and used the 396 for its true intended purpose
-- peace of mind. I could see the top-down weather picture and make
sure that the weather was not developing outside the scope of the
forecast. That is the way the 396 weather capability should be used --
not for close-in tactical avoidance. If you want to play that game, get
on-board radar and a stormscope...and even then second guess whether you
want to fly in those conditions.

A few caveats:

Keep in mind that I've seen shower activity (level 1, maybe 2) that does
NOT show up on the Garmin AT ALL. Do not expect to use the 396 to stay
dry. For whatever reason, it doesn't work that way.

Also, the 396's lightning data is derived from a network that records
cloud-to-ground strikes only. Cloud to cloud strikes are thus not shown
on the 396 -- you need a stormscope to see those.

Hope this helps. Safe flying,

-Doug

--------------------
Doug Vetter, ATP/CFI

http://www.dvatp.com
--------------------

"Doug Vetter" wrote:
I always stay clear of red, since it's always convective.

Not always, but it is probably safest to assume it is.

--
Dan
C172RG at BFM