On 6/6/2007 4:16:53 PM, "Dan Luke" wrote:

As to the "stale" business, in 200+ hours of using the product in the most
thunderstorm-infested region of the U. S., I have found 6-8 minute maximum
lag a non issue for avoiding CBs.

For strategic avoidance I agree but it still requires some thought. My
Bonanza is equipped with WSI downlinked weather displayed on an MX-20 moving
map, and WSI's refresh rates are normally 0 to 4 minutes old. I was under the
impression that NEXRAD could be up to five minutes old before being uplinked
to the delivery satellites (corrections appreciated). Therefore a worst-case
scenario is that the NEXRAD returns I see on my moving map could potentially
be up to nine minutes old.

At a groundspeed of 50 knots (my guess as to the average speed for a more
severe thunderstorm), nine minute-old data translates to about an 8 nautical
mile area ahead of the mature storm's direction as depicted on the moving
map. Thus, I add 8 nm to the recommended 10 to 20 nm (depending on storm
severity and type - frontal) to cover that lag time, assuming haze or IMC
prevents seeing the storm out the window.

What concerns me are those days where t-storms seem to be popping up
everywhere and returns go from light to intense in 15 minutes or less. In
those cases this relatively slow refresh rate makes flying through that zone
a bit of a butt clencher.

--
Peter