Reliable ETA80 Grib data containing dewpoint data

[Daniel Leins]

List,

I'm attempting to download and plot eta80km model data in skew-t and
plan view format.  I don't have any problems getting the data or
plotting what I want to, however I've noticed that the grib files don't
contain dewpoint data for all the levels available, or sometimes, the
grib file doesn't contain dewpoint data at all.  I've been downloading
from ftpprd.ncep.noaa.gov, and pulling in the nam.tXXz.awp211ZZ.tm00
files (the eta80km), but this doesn't contain dewpoint data.  Or, when I
download the grbgrd##.tm00, which I think is the eta40km, it contains
dewpoint data, but only at 6 levels.

Likewise, when I move away from downloading entire data sets, and
"'sdfopen
http://nomads.ncdc.noaa.gov:9090/dods/NCDC_NOAAPort_ETA/200504/20050414/meso-eta_212_20050414_1200_fff'",
no dewpoint data exists here either.

Does anyone know of a location where I can either download a full set of
grib data, one that contains as much dewpoint data at as many levels as
possible, or might anyone know of a dods server where I can get this
information?

I had another thought, since RH and temperature are available at every
level.  Would it be possible to derive dewpoint at every level using an
extremely re-arranged form or RH=100*(e/es).  Does anyone have an
equation spelled out in Grads that would solve for Td in this equation?
Is this even a reliable method though, does vapor pressure vary with height?

Any help would be appreciated,

Thanks,
Dan Leins