Question

For scientific issue #1, when you say estimate, would you like a 
finite number or whether the sign is positive or negative? Also 
how are we supposed to find the 1000hPa GRVT when all we have is 
the 500hPa GRVT?


Answer

Calculating the full number can tell you the strength of 
intensification or weakening by the 1000 hPa cyclone from one
period to the next. If you examine the approximate form of the
P-S Development Equation at

http://www.atms.unca.edu/dmiller/atms410/at410_fnlpro2013.html

you'll find that the ( )p0 in the GRVT term implies that this
equation gives you the geostrophic relative vorticity tendency
at the 1000 hPa level (this is what the "p0" indicates).