Warehouse lenders increased the dollar volume of their commitments to an estimated $31 billion in the third quarter, a 3.3 percent sequential improvement, according to survey figures compiled byInside Mortgage Finance. Compared to the same quarter a year ago, commitments fell by 11.4 percent. But a commitment to lend is just that. Many nonbank borrowers rack up commitments, but the real test of the health of warehouse lending is in usage rates. At First Tennessee Bank, for example, its commitments were...[Includes one data chart]