Question:

Can you break down the 700 mb maps? How do the variables coincide? and more specifically what is 
the importance of the relative humidity? When the map says "GFS Thinned" what does that mean exactly?

For the last column. What maps are we using to find the Z_1000 values? 

We are also curious about our method in solving for GRVT... first, we calculated LTHAD by multiplying 
the nLTHAD value obtained from the map by -9.8/f, and then used the known relationships to get LAD and 
LDIA. We assumed that the -9.8/f was then accounted for in the LAD and LDIA terms, so all we had to do 
wasad d GAVA + LTHAD + LAD + LDIA to get GRVT. But at the same time, our LTHAD, LAD, and LDIA terms were 
all negative, causing the GRVT to be negative, indicative of a weakening cyclone. 

Answer:

The 700 mb maps are to aid in the assessment of LDIA. Recall that LDIA is either "+" (contributing to
cyclogenesis) or zero. We are assuming latent heat release (LHR) is the only diabatic effect that is
important. LDIA is positive if the 700 mb RH and vertical velocity requirements are met; RH greater 
than or equal to 70% and upward vertical velocity. LDIA is zero if RH is less than 70% OR vertical
velocity is downward. GFS Thinned is the GFS model forecast fields with some of the output at some
isobaric levels removed (thinned) to keep the file size more manageable.

We discussed in class how GRVT and isobaric height tendencies are inversely related. You can use the
Project #9 case study to help figure out an estimate of an actual function by comparing known GRVT
and height tendencies from that case and fitting some sort of linear (or other polynomial) function
between GRVT as the independent variable and height tendency as the dependent variable. Whatever you
decide to do, be sure to spell out your methodology in your project description document.

You are correct in your nLTHAD calculations, the maps of nLAD will give you opposite the sign of the 
LAD term, so you technically need to multiply your nLAD value by "-1" to get the proper LAD sign. As
mentioned in the first paragraph, LDIA should never be negative. It is either positive or zero.

As you are experiencing, the sign of GRVT is pretty sensitive to your predicted future cyclone 
position. If you are consistently getting negative GRVT, but the 500 hPa map is indicative of a 
developing cyclone, you might want to consider that your future cyclone position might be off. If
this is true, you might investigate future cyclone positions that are showing signs of GAVA and LTHAD
that are consistent with a developing 1000 mb cyclone.